I watch a lot of geology, anthropology, archeaology, history, and science channels on TH-cam. I enjoy your channel, it’s one of my favorites. Thank you.
@geogirl The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. It could have happened over the area in the sky a small rock exploded in 1908 killed no one but destroy 200 miles worth of land imagine if it was ten times the size during 12800 yrs ago we pass through Torid meteor ☄️ showed twice a year June and September this scientific facts
@@GEOGIRL The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. We pass through torrid meteor ☄️ showers twice a yr June and September imagine if the rock that hit 12800 yrs ago exploded over land it wiped out megafauna and most of the Clovis ppl
@@suprememarkee1018 The best estimate I've seen for the Tunguska explosion is 15MT at a five mile altitude, in other words a high-altitude airburst version of the March 1, 1954 Castle Bravo shot.
Latest cause I've found (read about) WAS a meteor strike around that time ! It coincides with a crater found under the ice in Greenland that supposedly occurred in that time frame, and was the most likely cause of the renewed cooling !
Super nice summary of the YD cooling event. One puzzling thing about the YD, that has been the focus of my research and others who work in Chukotka, NE Siberia and parts of Alaska, is the apparent absence of a YD cooling in quite a few lacustrine and terrestrial depositional records.
Is that potentially a seasonal bias in the temperature proxies (i.e. too much summer signal, less affected, and not enough winter)? Alternatively, perhaps NE Siberia/Alaska lack cooling as a function of longitudinal position on the planetary wave structure induced by AMOC reductions (meaning SW flow is enhanced to warm the region). Over the Urals, the wintertime cooling was exceptionally strong and brought permafrost down to nearly 52°. Possibly the same in central/west Siberia, from our records.
The impact could have happened over the ground and destroyed the mega fauna and took out most the Clovis ppl! The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. No one was hurt but it was small rock 🪨 from space destroyed everything within 200 miles Imagine if this was a much bigger asteroid
Thanks for your videos! I was able to get my professional geology license in no small part to watching all your videos on repeat. Such good content and your presentation is great!
Sometimes it's more then 1 thing,what I've seen the last time supervolcano erupted in Europe was Italian 1 around 40,000 years ago.Neanderthals disappearance was around 39,000 years ago but I'm guessing they were already stressed European neanderthals had been isolated for like 100,000 years then came in to contact with CroMagnon I'm guessing they were getting exposed to alot of new diseases think I read somewhere measles entered into Europe with CroMagnon.Glaciers expanding & retreating a lot of mobility probably caused new pathogen to do a lot of damage.African Cheetahs & Lions were originally indigenous to North America they migrated into Africa.Last mammoths went extinct like 4000 years ago in Siberia right?
Your presentation only seems to get better with each video. Love your content and I learn so much with each video. It's so easily digestible as a layman. Also great bedtime/sleep video as well. Looking forward to the next one!
She failed to mention that there are over 160 peer reviewed papers that support an impact. She fails to imagine a shower of Tunguska size fragments of a disintegrating icy dustball comet hitting over large swathes of Earth. Remember South America, Europe and Siberia lost megafauna too and there are sites in the Levant where the destruction debris of whole settlements show multiple impact proxies. There is enormous bias against the YDIH from a a very few tenured Clovis First schooled professors who write deeply flawed papers titled The Younger Dryas Impact Hypothesis: A Requiem. I am undecided on what happened but I have had 50 years of daily exposure to the 'latest' science and understand almost every theory has a shelf life. I have also spent a year inside the climate industrial complex as a salaried employee of a leading environmental charity where as part of my post I would be in daily contact with other charities, NGO's, scientists and Politicians. The actual theory and evidence for anthropogenic climate change as put in this video is so corrupted as to make it all useless. It is cherry picked by the IPCC for a political agenda and challenged by literally 100s of solid scientists who are legally prevented from appearing on TV news, debates etc. From my perspective I have actually taken part in choreographed 'protests' on a climate change blamed issue where we arrived as the TV news camera's showed up, performed our little costumed chants just before the relevant minister came out of the parliament and did his piece to the same camera. The whole thing just a set up to introduce another restriction on our liberty in the name of climate change. The truth is as a species we are up to making adaptive measures to make a warming climate work for us. Annual Global Biomass production is up significantly with the warming. There is more life and its thriving. Good stewardship of the planet does not hinge on CO2. What the YDIH does is show us not just that a cometary snowball disintegrated on its trip round the sun, not that our barely prehistoric forefathers not just coped but thrived while the seas rose 80ft , country sized huge ice sheets suddenly vanished and continents burned. The changes they were forced to adapt to birthed civilisations as we know them. The YDIH raises inconvenient data that shows massive dramatic climate change that dwarves any anthropogenic induced effects that are barely understood due to agenda manipulation.
It occurs to me that a spike in iridium concentration in a rock layer doesn't necessarily have to mean a single large impact. It could still be from a sudden influx of iridium, but that iridium might have arrived in multiple objects. We have the various meteor showers (leonids, perseids, etc.) from objects that left a lot of material in an orbit that intersects ours. Given iridium's status as a siderophile, I expect it to be much more abundant in metallic objects derived from the cores of differentiated protoplanets, than in the kind of outer-solar-system objects that cause meteor showers. But if a high-eccentricity object such as a comet collided with a low-eccentricity one that could be metallic, a large amount of iridium could be left to arrive as meteor showers, with centuries' worth arriving over a few decades. Or a comet could just be so large that its meteor shower leaves enough material to produce a measurable iridium spike. Alternatively, it might be possible, given a sufficiently stable location, get a small local iridium spike by having deposition from terrestrial sources cease for decades while meteor dust continues to arrive at the usual rate. I imagine a snow field that accumulates year after year on flat land, getting almost thick enough to flow as a glacier but not quite, in an area with lower than average influx of terrestrial dust. Outflow of melt water could concentrate the meteor-enriched dust from the snow field in a few locations at the edge.
As an avid Native American projectile point collector, I can assure you the Clovis never went anywhere. We can see a direct progression in lithic types spanning thousands of years without interruption. First Clovis, then Redstone, Folsom, Cumberland, Beaver lake, Dalton, etc, etc.. All very closely related. In fact, they're still here.
There's a theory though Clovis point found in northern Europe that Clovis people were seal hunter that traveled along glacier,there seem to be more Clovis settlements on east coast.Then idea of later immigration along west Coast from Alaska
You're the 4th or 5th YT paleontology channel (Eons, Raptorchatter, North02, et al) I've seen having to debunk the YDIH; and have done the best job explaining it. The visuals help a lot!
Thanks - very cool and objective coverage of the YD. I read somewhere that the YD also caused arid conditions in the fertile crescent that led to, or at least coincided with, the origin of agriculture.
Thank you, Doc, -- another fascinating presentation -- my side focus in grad school was the old KT impact -- and all the subsequent impact events -- I look forward to all your ideas.
You continue to amaze me given your busy busy life. I loved this video & I also loved your strategic call today, the reaction here was actually acceptance 😊😉 and acknowledgement of your good judgement. ❤️
Nice analysis! Some five cents that I know from a random commenter: 1) Some proponents of the impact actually propose multiple, even prolonged, impacts from a comet debris field 2) Humans arrived in Americas long before the Younger Dryas cooling, at least 10000 years before according to confirmed sites, and human estimated population doesn't seem to be enough to cause over-hunting of the megafauna
Thank You Dr. Rachael. Wow second episode in just a few hours. That means when I focus on "Geo Girl" my thinking cap is on my peanut brain and I am trying to absorb as much as possible, whew..TM
A few corrections/comments: 1) you showed reconstructed temps is Greenland to explain the Younger Dryas (YD) - those are not global temps. Temperatures did not decrease in the southern hemisphere during the YD. Note that sea levels rose during the YD, so the ice sheets continued to melt during the YD. Global temperatures warm during at least the later half of the YD. 2) Because the YD is ~1300 years long, I have not seen any claims of a meteor/comet-induced (or volcanic) global winter connected to YD cooling. Impact or volcanic cooling would be very short-lived (less than a decade). The YDIH papers generally avoid explaining how an impact caused the YD, and instead focus on evidence of an impact around the YD. 3) There's no question that the Atlantic Meridional Overturning Circulation disruption is associated with the YD, and would cause cooling in the north hemisphere (esp. Greenland and Europe) and warming in Antarctica. The YDIH needs the impact to affect the AMOC to be relevant to YD cooling. 4) The ice sheets were shrinking long before the Bolling-Allerod (B/A) - global sea level rise is a good proxy for meltwater production, and sea level starting rising around 20,000 years ago (the B/A starts around 15,000 years ago). 5) its the shift in meltwater drainage in North America that would affect the AMOC. As the Laurentide Ice Sheet shrinks to within the Arctic drainage basin, a major component of meltwater would be routed away from the Gulf of Mexico into the Arctic and/or St. Lawrence (Atlantic) watersheds. This would happen at the end of every glacial cycle.
@@fp-ko7vg Try Google Scholar for finding papers. (1) Osman et al 2021 in Nature "Globally resolved surface temperatures..." is good for seeing global temperatures through the deglacial. (2) Look at any YDIH paper, and they don't spend time connecting how an impact causes the YD. (3) Wikipedia is fine for this - note the line "scientific consensus is that severe AMOC weakening explains the climatic effects of the YD" - and a citation.(4) Wikipedia "past sea level" has sources for global sea level since the last glacial maximum. (5) this is sort of self-evident. when you have a big North American ice sheet, it expands into the Mississippi drainage, and then at some point, when ice recedes, much of meltwater would shift into the Arctic and North Atlantic drainages.
This has always been one of my favorite topics that I could never fully keep up with-great overview! If you're interested, we looked in detail at the precise timing of Younger Dryas cooling and its synchroneity with Asian Monsoon weakening, using speleothems from W. Europe, China, and Brazil. We concluded that the inception of cooling predated the impact, which had minimal effect: Cheng et al., 2020, PNAS, doi:10.1073/pnas.2007869117
The latest YDIH I heard is that it was probably Percids meteor shower, with a chain of small impacts across northern american ice shield. This resulted in local shock diamonds and iridium deposits, but the combined effect added up to global cooling, maybe included another big impulse of fresh water leading to ocean circulation shutting down. "shrugs"
to the best of my knowledge, physics experiment show us that small impact over ice sheet leaves no crater, only broken ice and melted water. @@gravitonthongs1363
Part of the impact hypothesis is that modest size impacts *into 2 kilometer thick ice,* can leave very little evidence on the ground underneath while still having significant global effects. Small scale tests of hypervelocity projectiles have bolstered that. Also that YD event may have been multiple fragments hitting the ice sheets.
@@posticusmaximus1739 It's like yesterday in geologic time but 2km of ice is not trivial, it's fairly strong "rock" but lower density than most. Even among the biggest impacts don't leave km deep craters on dry land.
Hi there Geo Girl, as you know this is one of the favorite debates that I follow. While I tend to favor Impact, I enjoy hearing all the ideas and information. gfs
Rachel, that was a very interesting and concise illustration of the Younger Dryas. I have seen and read about it, but your presentation totally made it clear to me what likely happened-the AMOC collapsed. Thanks!
I'm glad you did a follow up on this extinction. It's interesting that impact proxies can be caused by terrestrial processes. But what can cause nano-diamonds or iridium deposits? Even if there was an impact, it doesn't mean it caused YD cooling or extinctions. This video kind of left me feeling there was more consensus about the K-Pg event than the YD, yet you clearly present the AMOC disruption as the accepted explanation for the Big Freeze. I'm guessing YDIH is more fringe? Anyway, I love these deep dives. It's great to have you explain subjects in a way I can understand and follow.
Thermal expansion of the oceans is much more important than the retraction contraction of ice over land when temperature rises. Talking about ice retracts and not talking about ocean expansion is very confusing because people tend to ignore the very big thermal expansion of the water in the oceans. Water has a volumetric expansion coeficient of 210 parts per million per each Kelvin or Celsius degree, but the apparent expansion coeficiente is much higher from the concentration of the volume expansion coeficient in one direction only because very often liquids are inside containers of much lower coeficients like glass of a thermometer, a glass of water, or the shapes of the seabed.
There were reports of the Mississippi River being frozen to New Orleans and ice floes in the northern Gulf of Mexico in 1784 after Iceland`s Laki Volcano began erupting in 1783. Imagine what a disaster this would be today? Even back then millions died and people in Europe choked to death on the toxic gasses. How many are aware of events like these? They`re very common, in fact, and we`ve been very very very lucky for an unusually long period now. Now you know. Get ready!
Thanks for speaking theoretically and indicating more study and data is needed. It’s so refreshing. Belief in Science has been damaged over the years by claims that theories are facts.
They shot themselves in the foot by publicly announcing that Mesoamerican bright white flying serpents, the superbolide phenomena, are about skin color! Also, denying that there are seven birds in a row under Pillar 18 of Gobekli Tepe, the symbology of the Pleiades, the radiant of our most recent meteor stream. And, The Carolina Bays are ice lakes that miraculously produced radiating, essentially parallel, elliptical depressions. Or, stating that we ate all those late Pleistocene megafauna into extinction. This all started in science with Halley, Newton, and Whiston. I have been at this for nine years and not one person has negated anything, they lost by default.
@@posticusmaximus1739 Thanks, I thought I was blocked once again. I can go on....... I compiled a 144,000 word compendium and I was being as brief as possible. See, academia have an aversion to space falls even though essentially everyone's traditions tell of The Taurid Meteor Stream being the causation of The World Ages of Man or Suns in Mesoamerica. And how could the ancients have known, in detail, of this inner solar system space debris when it was not "known" to science till the work of Dr. Fred Whipple in 1950? They knew from conditioning. Hard science of undeniable extraterrestrial proxies and a whole globe of witnesses versus the other side that has NOTHING. People must have lost the logic to evaluate things.
Meanwhile the industrial pollution going on amounts to an irresponsible climate change experiment on a global scale without regard to the need for further data or study.
Well done! But I see your list a vague possibilities and raise you 10,000 perfect elliptical features radiating from the Great Lakes region. They came from somewhere, are young and describe a spectacularly powerful event that turned everything living at these locations into paste. Carbon dating on the inverted stratigraphy of these structures dates to the YDB. As long as these features are in the geographic 'way' they will remain the very best evidence of all the hypotheses out there of what happened here: something hit the Laurentide Ice Sheet. NOTE: the freshwater from melted ice easily explains the disruption to the AMOC. Go guh, luv ya!
I suggest you take a closer look at the available information on these bays as their ages do not align with each other as would be expected if they were due to a single impact. Instead from carbon dating of sediments and even the study of pollen microfossils these have wildly variable ages ranging from MIS 5 (130,000-80,000 YBP) to only 440 ± 50 YBP i.e. the Holocene. Additionally optically stimulated luminescence has shown the Flamingo bay has some sand last exposed to sunlight on the order of 109,000 YBP well within the age range of MIS 5.
@@posticusmaximus1739See Antonio Zemoria's youtube videos on this subject. Summary: one or more comet fragments impacted the lorentide icesheet in the Great Lakes area. This impact sent huge ice bolders into the air raining back down on North America. These secondary impacts formed the Nebraska rainwater basins and Carolina bays. This impact contributed to the cooling at that time. The other factor (main factor) in the cooling was fresh water entering the ocean and slowing down the AMOC.
Here's a question.. What kind of evidence would we expect to see if an impact similar to the KPG happened, but right in the middle of the ocean? Or what if it landed on one of the thicker ice sheets in Antarctica? Would something like that be violent enough to go through the ice? What if there was 2-4km of ocean between it and the ocean floor, assuming no islands nearby.
I don't have answers, but another thing to consider for much older impacts would be that if it struck oceanic crust, that crust would likely get subducted back into the mantle later. However, that is a process that can take 10's or even over 100 million years. So, another possible scenario is "It impacted but the crater later subducted and that's why we can't find it," BUT so little crust subducts in jus 12,000 years that part of the crater would probably still be exposed, so that isn't really an option for a proposed Younger Dryas impactor. It could potentially explain a missing cratee for a much, much more anciemt impact, however.
@@lethargogpeterson4083 Well, I was more or less asking what evidence would there be if a impact happened on a very deep ice sheet or in the middle of the deep ocean
Sadly if you look into the Carolina bays while their origins are still enigmatic one striking result is that carbon dating of their oldest organic material reveal an extremely wide age distribution varying from many tens of thousands of years old i.e. too old to date via carbon 14 to ages that are only a few hundred years old ~440+/-50 years. This is also supported by the varying state of evolution of depressions from lakes to a varying progression of less and less water dominated wetlands with some having become completely infilled and only left distinguishable from their surroundings by having distinct sandy soils. Such a wide range in ages and geophysical lake infill evolutionary stages is pretty much impossible to explain via a single impact event you need some process which has been in operation throughout the Pleistocene and probably Holocene.
Sampling must be conducted at the lip of these structures looking for the overturned layers. This is the only way to properly date these structures. Older layers on top of younger layers on top of older layers is what you need to find. The wide range of dates is given to the different locations samples have been collected. To date I only know of two samples that have been documented to have been collected from the rims catching the right strata. The age dates did corospond to the YD impact time. Much more work must be conducted.
Dear Dr. Geo Girl, are you familiar with the Carolina Bays and Dr. Zamorra's ice impact theory? Perhaps you would entertain doing a show on this topic. Cheers from Italy.
Antonio Zamora's work on the Carolina Bays is indispensable. What other explanation can provide a fair analysis of the number and consistency of the ovals?
The shapes R truly unique and appear, ONLY, to be a result of the splattering of the Laurentide ice sheet, landing in NC and plenty of other places. Zamora has years of work posted, and , all of it is consistent from any angle, supporting reentry of ice boulders, on a parwith Benvenuto Cellini's ballistics. He did one recently that addresses timing, too.
@@posticusmaximus1739 I M not saying this incident was not unique. Nevertheless, Zamora talks about archeological evidence he thinks supports his larger assessment. I like what GEO GIRL indicates about the variance from other impacts. We don't have data on anything but this one ICE impact. A statistic of one's notable statistic. This seems 2B N issue here.
@@posticusmaximus1739 sorry, a statistic of one is not a statistic. And, Zamora's archeological evidence is from the southern hemisphere, having to do with dating...
Beyond that, she did not address the very rapid sea level rise due to the almost immediate melting and runoff of glaciers. It's hard to explain that without an enormous and sudden energy influx, such as a meteor or comet field striking the glaciers themselves. To me, Firestone et al, have proven their case.
@@billnorthrup7654 Sea-level rise was actually more rapid following the YD than during or before it (MWP-1B), and there's no difficulty explaining this from normal deglacial processes. The main issue with the YDIH is not whether there might have been impacts but the timing of those events with respect to the YD chronology. We found that globally synchronous cooling/drying predated the most precise ages of potential impact forcing. There's a lot more to discuss, but the most comprehensive reference would be Holliday et al. (2023; doi:10.1016/j.earscirev.2023.104502). It's a tricky issue, but I don't see growing support for impact(s) as the proximal cause of YD cooling.
@@billnorthrup7654 That so-called "very rapid sea level rise" never amounted to more than a few inches per *year.* Hardly the catastrophic flood some would have you believe it was. Nothing a snail could out-run by magnitudes is "catastrophic".
The AMOC was probably slowing down due to the influx of freshwater into the North Atlantic, causing cooling. Then along came a comet that impacted the lorentide icesheet in at least one location. So, there is no primary crater. The nebraska rainwater basins and Carolina bays are the secondary ice impacts from the comet impact. My understanding is that there are two other locations of impact around this time. One in South America and one in syria. Antonio Zamora has several youtube videos on this.
@terenceiutzi4003 The cooling is from the slowdown/shutdown of the AMOC, which brings warm water north. Right now, that is the worry due to fresh water entering the North Atlantic from the melt water from Greenland.
One thing I find intriguing regarding the extinctions, Clocvis culture, and beginning of agriculture is the possibility that the partially digested plant matter in ruminant stomachs was an important part of the human diet. What I haven't seen addressed is that if climate change caused the herbivores to starve, their stomachs would have been relatively empty. Then the humans who depended on them would have potentially needed to overhunt to make up for the loss of nutrienst causing extinctions of animals they formerly lived in balance with, and then drove the development of systematic agriculture after the large herbivores were extinct.
Not all impact events leave craters. If a field of objects the size of beach balls, many thousands of them, but with the total mass of say the Tunguska impactor entered the atmosphere and imploded the effect would be the same but there would be no crater. This is probably more common as iridium layers are more common as well in drill cores. Lots of unknown impact events.
As a a geo(hydro)logist I do a lot of research in the Namurian-Dinantian-Famennian-Frasnian (Upper-Carboniferous to Middle-Devonian) transitions right now for the construction of a deep surface gravitational wave detector. We found some layers in our deep boreholes at the Dutch/Belgium/German border area that might be related to extinction events Hangenberg event et cetera. In case of young Dryas, I would take into account that we have not the full info of human occupation, the smoking gun of the impact(s) we found some of the fragments. The energy involved for the large meltwater pulse my impression is that the impact could be the major cause for the megafauna extinctions. It also causes unexpected challenges to large animals. The humans could have added to the extinction of the megafauna, in the end there was a world wide civilisation that was very well develloped before this YDB event and quite a bit less after this event.
@@gravitonthongs1363 one of the craters in South America there were some impact fields. The one at the US-Canadian border is not found due to the presence of the thick Laurentian ice-sheet. But geophysical data, local geology in combination with the calculated trajectories based on shapes and position of the Carolina bays et cetera point towards it. Oh and over here in Netherlands and Belgium we also found a layer containing iridium from that age.
@@br2v the iridium is just regular cosmic flux. The Carolina bays are deflation hollows dated over a 100k year period. No geologist believes they are ejecta marks. What is this other “geophysical data” you refer to?
@@gravitonthongs1363 there are anomalys found in the great lake area, using micro gravitation and geomagnetics. But a lot of survey work needs to be done over there. The people of the Dutch geological that worked on it, think that it triggered Volcanism in the Eifel ( Laacher See (Koblenz area Germany) < 50 miles from where I live) . Antonio Zamora and even NASA did some great research .
Forgot to mention: the Younger Dryas Impact Hypothesis suggests the comet broke into fragments, hit the Northern Hemisphere, emptied Lake Agassiz and Lake Missoula, left erratics all over Washington, and the Willamette Meteorite is likely a fragment from that comet which was carried toward Washington just like the erratics were. Jerry Kroth, Ph.D.
Hm. A short answer is "The science doesn't know exactly so far." 🤔🙄 But at least we studied everything we could have get to 🤓 Thanks for the video, greetings to the cat 😌🐱
The Carolina Bays, as an artifact of secondary impacts (many) from an ice sheet impactor should be explored further. A very compelling body of evidence.
Her analysis is very likely correct. The theory is a meteor impacted on the ice sheet that was melting, but still covering the Great Lake region or further north. Nor further south because the ice no longer covered regions a few hundred miles south of the Great Lakes. Causing the extinction of animals near the impact site, hence the extinction of the animals of the Americas, but not the rest of the world. The problem with this is basic geography. The southern part of South America is a lot further from the alleged impact site than Europe. Yes, the animals that were further away, in southern South America became extinct while the animals much closer in Europe were not effected. It seems the critical factor, in the sudden extinction of the American megafauna, was not the distance in miles from the Great Lakes region, but whether a human could reach a region on foot, for the first time, regardless whether it was one thousand miles away or six thousand miles away. We need to look at the pattern of the extinction of megafauna as a whole, world wide. First disappearing in Eurasia and Australia, then later in the Americas. Basically, whenever expert hunters first suddenly appeared, the megafauna because extinct. A worldwide pattern that happened around the world. And continued into historical times when humans first showed up at islands. Modern humans arriving and extinctions go hand in hand. The great exception is Africa. Why Africa? Well, humans did not become great hunters overnight. They gradually became better and better over time. And modern humans first developed modern behavior in Africa. Giving megafauna there enough time to gradually a more cautious behavior and keep away from upright animals that at a glance don't appear to be much of a concern. But everywhere else there were no modern hunters, then suddenly there were, causing pretty immediate extinction unless the mega fauna could undergo immediate evolution, which they could not.
Your videos are always informative, and the information is well presented. I would agree with you that there is not enough evidence of an impact from space causing the rapid cooling at the Younger Dryas (named after an alpine flower actually). However, some of the things like above average levels of iridium, microdiamonds and spherules, plus the dark mats, that occur over a certain area, but not worldwide, could indicate that rather than an impact, it may have been a series of airbursts. Think of the Tunguska event in 1908 in Siberia, which seems to have been an airburst rather than an impact. It was devastating over quite a large area of fortunately little human habitation. I also think that the main reason for the extinction of the megafauna was human hunting. Being an Aussie, the megafauna in Australia, such as the giant short faced kangaroo, and the diprotodon, declined and became extinct after the human migration to Australia some 65,000 years ago. They hung on until about the time of the warming 20,000 years ago. The climate in Australia became warmer and drier, and the human population was larger. The predators such as the thylacaleo, and the giant goanna megalania, declined at the same time. You don't need a global catastrophe to explain those extinctions.
Would a single impact be able to cause > 1000 years of cooling anyway? If I recall correctly, the K-Pg impact winter is supposed to have only lasted a few decades, so (as a non-expert) I'd be surprised if a much smaller impact had caused much longer-lasting cooling. Or is the hypothesis about multiple impacts and/or different cooling mechanisms?
Comparing the KPG event to the YDIH is like comparing a minor fender bender to a high speed, head on collision between semi-trucks. The former was magnitudes of degrees larger than the latter. The evidence suggests multiple impacts over the coarse of several thousand years by fragments of the disintegrating Comet Encke. Populations of various mega-fauna would have been diminished enough over those multiple events to ultimately lead to they're extinction. Not suddenly eradicated like the dinosaurs.
Excellent presentation, BUT... 1) the human arrival into the America's has been pushed back to at least 23,000 BP, and this is from a number of North and South American sites. So, the idea of overhunting, especially given the millions of megafauna all over the continent/s (think the bison population before the coming of Europeans) and relatively low population density of human hunters doesn't make this scenario seem very likely, 2) one of the problems with the analysis of the YDIH is that it is seen as a single massive event, and not a series of smaller, but still devastating impacts in the oceans, over the ice sheet and air bursts over land. You have done a superb job of analyzing the one scenario (single impact) but there are others that need this type of in-depth consideration. 3) the megafaunal extinctions would have been drawn out, given the main destruction of such impact/s would have been on ecological niches and habitats. The idea that the firestorm of such an impact would have killed off all the megafauna in one week (month?) doesn't ring true, where collapsing habitats does make more sense. I could go on, and on and on... :-) but suffice it to say this has been an interest of mine for some time, and although I realize there are many problems with the YDI hypothesis, none of the other theories are "bullet-proof," at least not yet.
I agree with you on "the topics of this video". My point refers to the graph we first see at 1m 19s about the drastic temperature changes' during the ice ages. Notice that the temperature climbs' are all strait lines with no dips in their rate of climb, unlike the temperature drops that are far more erratic. Velancofsky (Probable mis spell?) was an A list academic travelling between Europe and the USA giving lectures from the 1910's on until he proposed that to cause an Ice age you first need a period of extreme heat. Seen in that light the difference between our current climatic era and the previos volatile one is not shown in how the last major ice age started but in the gentle way we came out of it. Since "Save the Amazon" in the 70/80's I have been trying to convince people we are heading for global warming BUT there is one aspect that remains unknown; will the heating become "Run Away" or as Velancofsky proposed 'All that extra moisture in the atmosphere suddenly cools and fall as vast amounts of snow thus causing an Ice age to start with a bang. I often quote an 'Ice Core' scientist I saw on a BBC documentary. while pointing at a two inch part of one of the cores. "That is the start of the last Ice Age , that is one year or two, not three".
Interstellar debris fields could be a cause of many extinction events. it is not just one asteroid, but many small objects, not more than grains of sand, but so much of it, it would affect the sun, and occasional larger objects if unlucky. Deep debris field of sand would also give our skies a different color tone, while cooling, and other colors with more intense blue or red variations depending on simulation parameters. It is worth checking out and evaluate.
What about the Gothenburg magnetic excursion? The reason I state this is that there was another extinction event 42k years ago during the Laschamp excursion. It seems to line up with these extinctions.
I’m not taking a position on the YDIH, but I was alive in the 80’s and remember the KPH impact “theory” also being denied all over in the media and academia. Yes, extraordinary theories require ample data, but…in the western world we tend to support free speech. And some people take advantage of this. Obstructionists and mischievous people are literally everywhere and cause trouble one daily basis. These obstructionists were very busy in the 80s opposing the KPG event, as were the people claiming cigarettes don’t cause cancer!😅 Are we seeing that now? I am sure at least one group or person involved with the YDIH opposition is. Are all of them? Also not likely.
Interesting how influencers like Rogan and Hancock can take a fringe theory and hyperpopularize it. I though fresh water dumping into the ocean and disrupting the AMOC was the most widely accepted theory but conspiracy theories seem to take precedence
Yeah its unfortunate especially since the combination of carbon dating optically stimulated luminescence and microfossil analysis from core samples show that Carolina bays do not have a single age like an impact would require instead having a broad minimum age distribution ranging over 100,000 years from pollen fossils matching MIS 5 (130,000 to 80,000 years) or OSL date of infill quartz sand deposits of ~109,000 years on the upper end to carbon dating giving minimum ages less than a thousand years. Likewise the range of infilling these bays have experienced varies from those still young enough to be lakes to ones which are entirely infilled and only discernable form their surroundings by their distinctive sandy soil and stratigraphic record. How could a feature with an age distribution like that possibly be due to an impact? It doesn't make any sense!
@Dragrath1 a Rogan disciple told me it was a swarm of asteroids that pulled into Earth's and periodically impacted the Earth over 1,000s of years. I think there is a emotional desire for cool theories and people will make up the most outlandish things to support the cool theory.
@@Dragrath1 "Carolina bays do not have a single age like an impact would require ... It doesn't make any sense!" Yes, it does. If the impactor is was a fragmented comet orbiting around the solar system then parts of it could have struck the Earth on multiple occasions, as the comet returned to the vicinity of Earth. With a widely fragmented comet, some of the returns might miss the Earth completely, or only provide a light impact, whereas others would be more severe. The comparison in the video with the impact from the15km diameter end-Cretaceous asteroid impact is unhelpful, since nothing of that nature is posited for the YD. If the Carolina bays were not caused by impact, as you suggest, how were they formed? They have every appearance of impacts caused by being struck a glancing blow.
Howdy Doc, I was wondering why your illustration showing the course of the melt water didn’t include the western, Scablands direction, so I googled it. Seems the onset of warming after the LGM was a variable period of warming and cooling. The Bølling Allerod, Older Dryas, addition warming, Younger Dryas wasn’t a smooth transition. Was the onset of warming relatively abrupt?
I'm guessing simplified illustration since the Pacific Ocean has a completely different circulation pattern, basically from being wider. Since Europe sticks out further west as it goes south, this interrupts and slows the gyre that should take place there, letting cold water build up in the north until it does sink. Then, when trade winds would normally cause upwelling a bit further south, Africa folds back east, letting water be drawn from a more equatorial area instead of being forced up from the bottom, further enhancing that slow northward flow in the Atlantic.
@@soakupthesunman Imagine thinking an illustration whose aims are merely to show that there is a difference between warm (red) water and cool water circulation in the ocean, distributed around the globe, on a projection of a globe on a flat plane... is intended to be complete and in the perspective you want. In reality, the global ocean circulation covers everything in the water. Anytime you see an arrow on the water it is merely to indicate to you some aspect, such as direction. This is analogous to drawing vector lines when trying to illustrate a field, such as a magnetic field.
I don't think the impact caused the Younger Dryas, I think it's a coincidence. There seems to be evidence of multiple impacts over a period of tens of thousands of years prior to the Younger Dryas. The paper "Impact-related microspherules in Late Pleistocene Alaskan and Yukon “muck” deposits signify recurrent episodes of catastrophic emplacement" - Jonathan T. Hagstrum, et al., gives evidence of these prior impact events. If this paper is correct, then it seems likely that while a series of impacts did occur, they are not directly responsible for the Younger Dryas and associated extinctions. I think it is more likely that the Younger Dryas was inevitable, part of the natural processes at play, and that it is more likely that the Younger Dryas was the primary cause of these extinctions.
9:10 "dates just don't align".....a giant comet flyby, gets dismanteled.... and then some more stuff came in and also into the sun...so it would be a mix of CME's and Asteroïdes for while.
@@posticusmaximus1739 hi, usually someone who disagree will explain why it's not possible. ( i memt over many hundred years...) so the ENKI , meteor stream that crosses Earth's path twice a Year is BS? Thunguska is exacly is the dates and the direction is pretty accurate too... i'm vurious to know why you think it's not a plausable hypothesis.... ( sorry for my poor english ⚜️)
@@posticusmaximus1739 haha, this is rapidly twisting into a philosophical question. "If someone in your opinion makes no sense while emitting his idea on a presented subject, why reveling publicly your empty opinion but not doing the demonstation or explaining why when asked?
About the AMOC, I can see why salty cold water should be sinking in the north Atlantic, water evaporates from the surface, taking away heat and concentrating salt, but why should water be upwelling in the Pacific and Indian oceans. This woud suggest that this water is somehow getting less salty and/or warmer, and I don't see why this should be happening in the depths. There would have to be some deep source of heat or fresh water..
This guy: www.youtube.com/@Antonio_Zamora ... he gets into this idea a LOT. Kinda made it sound like a modest impact hitting the ice sheet directly, causing a splash effect of smaller impacts (almost like flying shards of glacier) spread outward as far as the carolinas. Sounded interesting at the time the algorithm was putting it in front of me.
I know that in my lifetime, I've been shocked by how much earth has regurgitated itself under my feet in regions I visited. This is due to the extreme gradualism we were taught. That said, this would've no doubt been a very dynamically chaotic but beautiful age that none of us would want to be in lol
So why isn't the younger dryas just part of the preceding cycles? It should be noted that there were other times when cooling took place subsequent to this.
Because we can tell that its timing did not match up with the periodicity of the Earth's astronomical (orbit, precession, & tilt) changes. The previous cycles were controled by these factors on their periodic timeline. That is why the Younger Dryas has warranted so much study because it didn't match up and thus, required some other cause(s). Sorry if I didn't make that clear in the video! ;)
Hey Geo Girl, wanna see the whole and way more complex picture of the younger dryas impact? There is a crater, that caused the earth's crust shift, which led to the end of the ice age, the permafrost in Siberia, Alaska and Canada, and the extinction of the mammoths, that were frozen in ice alive in north of Russia. All that and many more I talk about in my presentation I worked on completely alone for 2 years, and published it just about 3 weeks ago! And yea, it's way more massive then people in the west are prepared to see. Regards, Anatoly
One thing to look at is: get that chart out for the entire last ice age. The same odd glitch in the temp chart can be seen at least three times before the Younger Dryas! 😮. It’s weird and I haven’t heard a good explanation for any of them. 😢. What did that the same way several times? …. The megafauna had over 8,000 years to adapt to humans and Clovis culture nearly disappeared at the same time of megafauna extinction. … The Carolina Bays are very curious 🎉
The draining of Lake Agassiz. Is a really interesting topic? From what I understand very little evidence of this major event exists because it probably occurred over Ice. The Ice Age Floods in the Pacific NW that have a lot of evidence display what a massive powerful event this was.
The Younger Dryas likely had very little to do with megafaunal extinctions seeing as similar fluctuations occurred during past interglacials as well, also as a result of ocean current disruptions, without killing off megafauna.
Maybe... The YD is still fairly unique in terms of its magnitude and abruptness of cooling. To date, we haven't documented an analogous event during past deglaciations. Add to that human expansion as an ecological pressure, and that climatic shift-even if previously experienced-becomes all the more potent on megafaunal populations.
@@bkjeong4302 So MIS-5e specifically? Not so much, at least not like the Younger Dryas. Better candidates are at the MIS-16/15 and possibly MIS-12/11 terminations, but we don't have any high-res constraints suggesting they were comparable in magnitude or abruptness of cooling. Only that there were analogous termination-ice surging events. A friend of mine published about a Heinrich-analogous event at the stage 8/7e boundary, but likened it rather to H1 and H2-not the Younger Dryas. Long story short, the YD is very unique as a climate anomaly, in magnitude, rate, and timing (very late in the deglaciation) in the context of the Late Pleistocene.
To "retreat" defined by Meriam: "An act of going away from something difficult, dangerous, or disagreable." Glaciers DO NOT "retreat", they STAGNATE and MELT. Just fundimental physics, and definitions. Important to a geologist.
If the most likely cause of the Youger Dryas was the disruption of AMOC by freshwater due to glacial melt, is there evidence that other post glaical warming periods were also followed by periods of post-glacial cooling, synonymous with the Younger Dryas?
It's hard to address such things comets generally do not leave impact craters . It may not have been anything other than a dust cloud passing through the solar system / as for the clovis people they survived ( imagine archaeologist always assume people of the past go extinct but we fail to understand that people of any time period are very smart and tenacious!
I watch a lot of geology, anthropology, archeaology, history, and science channels on TH-cam. I enjoy your channel, it’s one of my favorites. Thank you.
Thank you so much! That means so much to me :D
@geogirl The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. It could have happened over the area in the sky a small rock exploded in 1908 killed no one but destroy 200 miles worth of land imagine if it was ten times the size during 12800 yrs ago we pass through Torid meteor ☄️ showed twice a year June and September this scientific facts
@@GEOGIRL The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. We pass through torrid meteor ☄️ showers twice a yr June and September imagine if the rock that hit 12800 yrs ago exploded over land it wiped out megafauna and most of the Clovis ppl
@@suprememarkee1018 The best estimate I've seen for the Tunguska explosion is 15MT at a five mile altitude, in other words a high-altitude airburst version of the March 1, 1954 Castle Bravo shot.
Latest cause I've found (read about) WAS a meteor strike around that time ! It coincides with a crater found under the ice in Greenland that supposedly occurred in that time frame, and was the most likely cause of the renewed cooling !
Super nice summary of the YD cooling event. One puzzling thing about the YD, that has been the focus of my research and others who work in Chukotka, NE Siberia and parts of Alaska, is the apparent absence of a YD cooling in quite a few lacustrine and terrestrial depositional records.
Interesting. Has any of this been published yet?
Is that potentially a seasonal bias in the temperature proxies (i.e. too much summer signal, less affected, and not enough winter)? Alternatively, perhaps NE Siberia/Alaska lack cooling as a function of longitudinal position on the planetary wave structure induced by AMOC reductions (meaning SW flow is enhanced to warm the region). Over the Urals, the wintertime cooling was exceptionally strong and brought permafrost down to nearly 52°. Possibly the same in central/west Siberia, from our records.
The impact could have happened over the ground and destroyed the mega fauna and took out most the Clovis ppl! The Tunguska event was a large explosion of between 3 and 50 megatons that occurred near the Podkamennaya Tunguska River in Yeniseysk Governorate, Russia, on the morning of 30 June 1908. No one was hurt but it was small rock 🪨 from space destroyed everything within 200 miles Imagine if this was a much bigger asteroid
Thanks for your videos! I was able to get my professional geology license in no small part to watching all your videos on repeat. Such good content and your presentation is great!
Thank you so much for this comment, I am so glad to hear that!
Sometimes it's more then 1 thing,what I've seen the last time supervolcano erupted in Europe was Italian 1 around 40,000 years ago.Neanderthals disappearance was around 39,000 years ago but I'm guessing they were already stressed European neanderthals had been isolated for like 100,000 years then came in to contact with CroMagnon I'm guessing they were getting exposed to alot of new diseases think I read somewhere measles entered into Europe with CroMagnon.Glaciers expanding & retreating a lot of mobility probably caused new pathogen to do a lot of damage.African Cheetahs & Lions were originally indigenous to North America they migrated into Africa.Last mammoths went extinct like 4000 years ago in Siberia right?
Your presentation only seems to get better with each video. Love your content and I learn so much with each video. It's so easily digestible as a layman.
Also great bedtime/sleep video as well. Looking forward to the next one!
G chick is a teacher in university!🤓
So glad to hear that! I try to get better with every video, so it really means a lot that it comes across! :D
I really appreciate all those clarifications. Excellent research .You rock Dr. 👍
She failed to mention that there are over 160 peer reviewed papers that support an impact. She fails to imagine a shower of Tunguska size fragments of a disintegrating icy dustball comet hitting over large swathes of Earth. Remember South America, Europe and Siberia lost megafauna too and there are sites in the Levant where the destruction debris of whole settlements show multiple impact proxies.
There is enormous bias against the YDIH from a a very few tenured Clovis First schooled professors who write deeply flawed papers titled The Younger Dryas Impact Hypothesis: A Requiem. I am undecided on what happened but I have had 50 years of daily exposure to the 'latest' science and understand almost every theory has a shelf life. I have also spent a year inside the climate industrial complex as a salaried employee of a leading environmental charity where as part of my post I would be in daily contact with other charities, NGO's, scientists and Politicians. The actual theory and evidence for anthropogenic climate change as put in this video is so corrupted as to make it all useless. It is cherry picked by the IPCC for a political agenda and challenged by literally 100s of solid scientists who are legally prevented from appearing on TV news, debates etc.
From my perspective I have actually taken part in choreographed 'protests' on a climate change blamed issue where we arrived as the TV news camera's showed up, performed our little costumed chants just before the relevant minister came out of the parliament and did his piece to the same camera. The whole thing just a set up to introduce another restriction on our liberty in the name of climate change. The truth is as a species we are up to making adaptive measures to make a warming climate work for us. Annual Global Biomass production is up significantly with the warming. There is more life and its thriving. Good stewardship of the planet does not hinge on CO2. What the YDIH does is show us not just that a cometary snowball disintegrated on its trip round the sun, not that our barely prehistoric forefathers not just coped but thrived while the seas rose 80ft , country sized huge ice sheets suddenly vanished and continents burned. The changes they were forced to adapt to birthed civilisations as we know them. The YDIH raises inconvenient data that shows massive dramatic climate change that dwarves any anthropogenic induced effects that are barely understood due to agenda manipulation.
It occurs to me that a spike in iridium concentration in a rock layer doesn't necessarily have to mean a single large impact. It could still be from a sudden influx of iridium, but that iridium might have arrived in multiple objects. We have the various meteor showers (leonids, perseids, etc.) from objects that left a lot of material in an orbit that intersects ours. Given iridium's status as a siderophile, I expect it to be much more abundant in metallic objects derived from the cores of differentiated protoplanets, than in the kind of outer-solar-system objects that cause meteor showers. But if a high-eccentricity object such as a comet collided with a low-eccentricity one that could be metallic, a large amount of iridium could be left to arrive as meteor showers, with centuries' worth arriving over a few decades. Or a comet could just be so large that its meteor shower leaves enough material to produce a measurable iridium spike.
Alternatively, it might be possible, given a sufficiently stable location, get a small local iridium spike by having deposition from terrestrial sources cease for decades while meteor dust continues to arrive at the usual rate. I imagine a snow field that accumulates year after year on flat land, getting almost thick enough to flow as a glacier but not quite, in an area with lower than average influx of terrestrial dust. Outflow of melt water could concentrate the meteor-enriched dust from the snow field in a few locations at the edge.
As an avid Native American projectile point collector, I can assure you the Clovis never went anywhere. We can see a direct progression in lithic types spanning thousands of years without interruption.
First Clovis, then Redstone, Folsom, Cumberland, Beaver lake, Dalton, etc, etc.. All very closely related.
In fact, they're still here.
Oh God, where?!
There's a theory though Clovis point found in northern Europe that Clovis people were seal hunter that traveled along glacier,there seem to be more Clovis settlements on east coast.Then idea of later immigration along west Coast from Alaska
Yes! One of my favorite topics!!! Thank you for another great video!
Younger Dryas sounds like it could be a Jethro Tull song title.
I named my cat Younger Dryas and then he died.
It's actually the name of an alpine flower whose presence shows up in the fossil record during this period.
You're the 4th or 5th YT paleontology channel (Eons, Raptorchatter, North02, et al) I've seen having to debunk the YDIH; and have done the best job explaining it. The visuals help a lot!
The impact theory has not been debunked. Nice try.
@justmenotyou3151 debunked several times over, Rachel just debunked it too. Come back with evidence and consensus of the scientific community.
@posticusmaximus1739 Efforts are underway and the evidence is building.
@@posticusmaximus1739 Yes, and I contested it at that time as well.
@justmenotyou3151 what about general consensus of the paleontological community? "Evidence" from rogue scientists is inadequate.
Thanks - very cool and objective coverage of the YD. I read somewhere that the YD also caused arid conditions in the fertile crescent that led to, or at least coincided with, the origin of agriculture.
Thank you, Doc, -- another fascinating presentation -- my side focus in grad school was the old KT impact -- and all the subsequent impact events -- I look forward to all your ideas.
You continue to amaze me given your busy busy life. I loved this video & I also loved your strategic call today, the reaction here was actually acceptance 😊😉 and acknowledgement of your good judgement. ❤️
Glad to hear that! :)
Nice analysis! Some five cents that I know from a random commenter:
1) Some proponents of the impact actually propose multiple, even prolonged, impacts from a comet debris field
2) Humans arrived in Americas long before the Younger Dryas cooling, at least 10000 years before according to confirmed sites, and human estimated population doesn't seem to be enough to cause over-hunting of the megafauna
Geo Girl always makes my day! ❤🎉😊
Wonderful discussion Rachel. Absolutely fascinating. Thank you for all your good works. You have such a great gift and I truly appreciate it.
Thank You Dr. Rachael. Wow second episode in just a few hours. That means when I focus on "Geo Girl" my thinking cap is on my peanut brain and I am trying to absorb as much as possible, whew..TM
A few corrections/comments:
1) you showed reconstructed temps is Greenland to explain the Younger Dryas (YD) - those are not global temps. Temperatures did not decrease in the southern hemisphere during the YD. Note that sea levels rose during the YD, so the ice sheets continued to melt during the YD. Global temperatures warm during at least the later half of the YD.
2) Because the YD is ~1300 years long, I have not seen any claims of a meteor/comet-induced (or volcanic) global winter connected to YD cooling. Impact or volcanic cooling would be very short-lived (less than a decade). The YDIH papers generally avoid explaining how an impact caused the YD, and instead focus on evidence of an impact around the YD.
3) There's no question that the Atlantic Meridional Overturning Circulation disruption is associated with the YD, and would cause cooling in the north hemisphere (esp. Greenland and Europe) and warming in Antarctica. The YDIH needs the impact to affect the AMOC to be relevant to YD cooling.
4) The ice sheets were shrinking long before the Bolling-Allerod (B/A) - global sea level rise is a good proxy for meltwater production, and sea level starting rising around 20,000 years ago (the B/A starts around 15,000 years ago).
5) its the shift in meltwater drainage in North America that would affect the AMOC. As the Laurentide Ice Sheet shrinks to within the Arctic drainage basin, a major component of meltwater would be routed away from the Gulf of Mexico into the Arctic and/or St. Lawrence (Atlantic) watersheds. This would happen at the end of every glacial cycle.
Interesting, could you give some bibliography or recommendations for that?
@@fp-ko7vg Try Google Scholar for finding papers. (1) Osman et al 2021 in Nature "Globally resolved surface temperatures..." is good for seeing global temperatures through the deglacial. (2) Look at any YDIH paper, and they don't spend time connecting how an impact causes the YD. (3) Wikipedia is fine for this - note the line "scientific consensus is that severe AMOC weakening explains the climatic effects of the YD" - and a citation.(4) Wikipedia "past sea level" has sources for global sea level since the last glacial maximum. (5) this is sort of self-evident. when you have a big North American ice sheet, it expands into the Mississippi drainage, and then at some point, when ice recedes, much of meltwater would shift into the Arctic and North Atlantic drainages.
The cat: "Dont TH-cam. PET ME NEOW" 😸
She is very needy sometimes haha ;)
Thank you for the clarity and references!!
This has always been one of my favorite topics that I could never fully keep up with-great overview! If you're interested, we looked in detail at the precise timing of Younger Dryas cooling and its synchroneity with Asian Monsoon weakening, using speleothems from W. Europe, China, and Brazil. We concluded that the inception of cooling predated the impact, which had minimal effect: Cheng et al., 2020, PNAS, doi:10.1073/pnas.2007869117
That would make sense given the amount of fresh melt water being released into the oceans at that time.
The latest YDIH I heard is that it was probably Percids meteor shower, with a chain of small impacts across northern american ice shield. This resulted in local shock diamonds and iridium deposits, but the combined effect added up to global cooling, maybe included another big impulse of fresh water leading to ocean circulation shutting down. "shrugs"
We haven’t found one impact site let alone many. All they found was general cosmic flux
to the best of my knowledge, physics experiment show us that small impact over ice sheet leaves no crater, only broken ice and melted water. @@gravitonthongs1363
Part of the impact hypothesis is that modest size impacts *into 2 kilometer thick ice,* can leave very little evidence on the ground underneath while still having significant global effects. Small scale tests of hypervelocity projectiles have bolstered that. Also that YD event may have been multiple fragments hitting the ice sheets.
@@Mrbfgray over thousands of years?
@@posticusmaximus1739 It's like yesterday in geologic time but 2km of ice is not trivial, it's fairly strong "rock" but lower density than most. Even among the biggest impacts don't leave km deep craters on dry land.
@Mrbfgray it was a UFO not an asteroid
@@posticusmaximus1739 Sure, likely cometary fragments but currently unidentified.
@@posticusmaximus1739 Sure--cometary fragments likely but currently unidentified.
Hi there Geo Girl, as you know this is one of the favorite debates that I follow. While I tend to favor Impact, I enjoy hearing all the ideas and information. gfs
Rachel, that was a very interesting and concise illustration of the Younger Dryas. I have seen and read about it, but your presentation totally made it clear to me what likely happened-the AMOC collapsed.
Thanks!
Rachel 🪄, Excellent topic 📑 and excellent production 💻. Thank you very much.
👏👏👏👏👏👏
Thanks so much Michael! :D
I love your content so much. Thank you for making geology content accessible.
Very good Video, I do like the scientific style. My summary: At least the "Meow-Fauna" is still quite alive, as we can see. 😅
Oh yes, the meow-fauna is very alive and well lol!😂
I'm glad you did a follow up on this extinction. It's interesting that impact proxies can be caused by terrestrial processes. But what can cause nano-diamonds or iridium deposits? Even if there was an impact, it doesn't mean it caused YD cooling or extinctions. This video kind of left me feeling there was more consensus about the K-Pg event than the YD, yet you clearly present the AMOC disruption as the accepted explanation for the Big Freeze. I'm guessing YDIH is more fringe? Anyway, I love these deep dives. It's great to have you explain subjects in a way I can understand and follow.
YDIH is almost on par with Aliens building the pyramids. It's only trending due to the rise of social media and influencers pushing disinformation
Your cat is always welcome to make an appearance.
😆
Oh she will love this comment! haha ;)
Awesome presentation! Thanks so much!
Thermal expansion of the oceans is much more important than the retraction contraction of ice over land when temperature rises.
Talking about ice retracts and not talking about ocean expansion is very confusing because people tend to ignore the very big thermal expansion of the water in the oceans.
Water has a volumetric expansion coeficient of 210 parts per million per each Kelvin or Celsius degree, but the apparent expansion coeficiente is much higher from the concentration of the volume expansion coeficient in one direction only because very often liquids are inside containers of much lower coeficients like glass of a thermometer, a glass of water, or the shapes of the seabed.
Thank you Dr Phillips.
Obrigado!
There were reports of the Mississippi River being frozen to New Orleans and ice floes in the northern Gulf of Mexico in 1784 after Iceland`s Laki Volcano began erupting in 1783. Imagine what a disaster this would be today? Even back then millions died and people in Europe choked to death on the toxic gasses. How many are aware of events like these? They`re very common, in fact, and we`ve been very very very lucky for an unusually long period now. Now you know. Get ready!
Happening now with all the volcanic activity
Thank you for this one! I have to agree with the others who have said you are the best.
The Hancock fanboys are going to be screaming in outrage.
Thanks for speaking theoretically and indicating more study and data is needed. It’s so refreshing. Belief in Science has been damaged over the years by claims that theories are facts.
They shot themselves in the foot by publicly announcing that Mesoamerican bright white flying serpents, the superbolide phenomena, are about skin color! Also, denying that there are seven birds in a row under Pillar 18 of Gobekli Tepe, the symbology of the Pleiades, the radiant of our most recent meteor stream. And, The Carolina Bays are ice lakes that miraculously produced radiating, essentially parallel, elliptical depressions. Or, stating that we ate all those late Pleistocene megafauna into extinction. This all started in science with Halley, Newton, and Whiston. I have been at this for nine years and not one person has negated anything, they lost by default.
Yes, conspiracies are being propagated all around us and science is being rejected more and more
@@bardmadsen6956yeah, what you said!
@@posticusmaximus1739 Thanks, I thought I was blocked once again. I can go on....... I compiled a 144,000 word compendium and I was being as brief as possible. See, academia have an aversion to space falls even though essentially everyone's traditions tell of The Taurid Meteor Stream being the causation of The World Ages of Man or Suns in Mesoamerica. And how could the ancients have known, in detail, of this inner solar system space debris when it was not "known" to science till the work of Dr. Fred Whipple in 1950? They knew from conditioning. Hard science of undeniable extraterrestrial proxies and a whole globe of witnesses versus the other side that has NOTHING. People must have lost the logic to evaluate things.
Meanwhile the industrial pollution going on amounts to an irresponsible climate change experiment on a global scale without regard to the need for further data or study.
Well done! But I see your list a vague possibilities and raise you 10,000 perfect elliptical features radiating from the Great Lakes region. They came from somewhere, are young and describe a spectacularly powerful event that turned everything living at these locations into paste. Carbon dating on the inverted stratigraphy of these structures dates to the YDB. As long as these features are in the geographic 'way' they will remain the very best evidence of all the hypotheses out there of what happened here: something hit the Laurentide Ice Sheet. NOTE: the freshwater from melted ice easily explains the disruption to the AMOC. Go guh, luv ya!
They are deflation hollows formed over a 100k year period. No geologists think they are impact marks.
I think the Carolina bays geological features are some evidence of an impact event.
And...?
I suggest you take a closer look at the available information on these bays as their ages do not align with each other as would be expected if they were due to a single impact. Instead from carbon dating of sediments and even the study of pollen microfossils these have wildly variable ages ranging from MIS 5 (130,000-80,000 YBP) to only 440 ± 50 YBP i.e. the Holocene. Additionally optically stimulated luminescence has shown the Flamingo bay has some sand last exposed to sunlight on the order of 109,000 YBP well within the age range of MIS 5.
@@posticusmaximus1739See Antonio Zemoria's youtube videos on this subject. Summary: one or more comet fragments impacted the lorentide icesheet in the Great Lakes area. This impact sent huge ice bolders into the air raining back down on North America. These secondary impacts formed the Nebraska rainwater basins and Carolina bays. This impact contributed to the cooling at that time. The other factor (main factor) in the cooling was fresh water entering the ocean and slowing down the AMOC.
Here's a question.. What kind of evidence would we expect to see if an impact similar to the KPG happened, but right in the middle of the ocean? Or what if it landed on one of the thicker ice sheets in Antarctica? Would something like that be violent enough to go through the ice? What if there was 2-4km of ocean between it and the ocean floor, assuming no islands nearby.
I don't have answers, but another thing to consider for much older impacts would be that if it struck oceanic crust, that crust would likely get subducted back into the mantle later. However, that is a process that can take 10's or even over 100 million years. So, another possible scenario is "It impacted but the crater later subducted and that's why we can't find it," BUT so little crust subducts in jus 12,000 years that part of the crater would probably still be exposed, so that isn't really an option for a proposed Younger Dryas impactor. It could potentially explain a missing cratee for a much, much more anciemt impact, however.
@@lethargogpeterson4083 Well, I was more or less asking what evidence would there be if a impact happened on a very deep ice sheet or in the middle of the deep ocean
You might view some of the Carolina Bays up close. Fascinating geology. An ice comet hitting the ice cap explains much...
Your comment grammatically doesn't make sense
Makes total sense to those in the know. @@posticusmaximus1739
Sadly if you look into the Carolina bays while their origins are still enigmatic one striking result is that carbon dating of their oldest organic material reveal an extremely wide age distribution varying from many tens of thousands of years old i.e. too old to date via carbon 14 to ages that are only a few hundred years old ~440+/-50 years. This is also supported by the varying state of evolution of depressions from lakes to a varying progression of less and less water dominated wetlands with some having become completely infilled and only left distinguishable from their surroundings by having distinct sandy soils.
Such a wide range in ages and geophysical lake infill evolutionary stages is pretty much impossible to explain via a single impact event you need some process which has been in operation throughout the Pleistocene and probably Holocene.
Sampling must be conducted at the lip of these structures looking for the overturned layers. This is the only way to properly date these structures. Older layers on top of younger layers on top of older layers is what you need to find. The wide range of dates is given to the different locations samples have been collected. To date I only know of two samples that have been documented to have been collected from the rims catching the right strata. The age dates did corospond to the YD impact time. Much more work must be conducted.
@@justmenotyou3151It is common to see younger Carolina bay sand rims overlying older Carolina bay deposits because of bay migration.
Dear Dr. Geo Girl, are you familiar with the Carolina Bays and Dr. Zamorra's ice impact theory? Perhaps you would entertain doing a show on this topic. Cheers from Italy.
Can you enlighten us about the bays of Carolina?
Great video. Hoping you get 1 mil subscribers soon 🎉🎉👍
Antonio Zamora's work on the Carolina Bays is indispensable. What other explanation can provide a fair analysis of the number and consistency of the ovals?
Elaborate please
The shapes R truly unique and appear, ONLY, to be a result of the splattering of the Laurentide ice sheet, landing in NC and plenty of other places. Zamora has years of work posted, and , all of it is consistent from any angle, supporting reentry of ice boulders, on a parwith Benvenuto Cellini's ballistics. He did one recently that addresses timing, too.
@@RobertMStahl why did the lower hemisphere warm up at this time?
@@posticusmaximus1739
I M not saying this incident was not unique. Nevertheless, Zamora talks about archeological evidence he thinks supports his larger assessment. I like what GEO GIRL indicates about the variance from other impacts. We don't have data on anything but this one ICE impact. A statistic of one's notable statistic. This seems 2B N issue here.
@@posticusmaximus1739 sorry, a statistic of one is not a statistic. And, Zamora's archeological evidence is from the southern hemisphere, having to do with dating...
Thank a lot for this video , it helped me a lot in my project and upcoming exams . Thanks a lot.....😘
❤ Solid evidence. I love data!
The many peer-reviewed papers that present the impact hypothesis, DO NOT propose a single impact.
They propose multiple impacts.
Read the papers.
Beyond that, she did not address the very rapid sea level rise due to the almost immediate melting and runoff of glaciers. It's hard to explain that without an enormous and sudden energy influx, such as a meteor or comet field striking the glaciers themselves. To me, Firestone et al, have proven their case.
@@billnorthrup7654 Sea-level rise was actually more rapid following the YD than during or before it (MWP-1B), and there's no difficulty explaining this from normal deglacial processes.
The main issue with the YDIH is not whether there might have been impacts but the timing of those events with respect to the YD chronology. We found that globally synchronous cooling/drying predated the most precise ages of potential impact forcing.
There's a lot more to discuss, but the most comprehensive reference would be Holliday et al. (2023; doi:10.1016/j.earscirev.2023.104502). It's a tricky issue, but I don't see growing support for impact(s) as the proximal cause of YD cooling.
@@ageofrocks disagree. that's fine
BUT FIRST, we drink Graham Hancock's koolaid
@@billnorthrup7654 That so-called "very rapid sea level rise" never amounted to more than a few inches per *year.* Hardly the catastrophic flood some would have you believe it was. Nothing a snail could out-run by magnitudes is "catastrophic".
The AMOC was probably slowing down due to the influx of freshwater into the North Atlantic, causing cooling. Then along came a comet that impacted the lorentide icesheet in at least one location. So, there is no primary crater. The nebraska rainwater basins and Carolina bays are the secondary ice impacts from the comet impact. My understanding is that there are two other locations of impact around this time. One in South America and one in syria. Antonio Zamora has several youtube videos on this.
You do realize that fresh water freezes well above the temperature of the north Atlantic! So it would be adding warm water!
@terenceiutzi4003 The cooling is from the slowdown/shutdown of the AMOC, which brings warm water north. Right now, that is the worry due to fresh water entering the North Atlantic from the melt water from Greenland.
@justmenotyou3151 So where did the fresh water come from 30,000 years ago and every 30,000 years before that?
@justmenotyou3151 If you want people to believe your lies, you have to first destroy all history like Orwell said you would have to!
You're the best Geo Girl!
One thing I find intriguing regarding the extinctions, Clocvis culture, and beginning of agriculture is the possibility that the partially digested plant matter in ruminant stomachs was an important part of the human diet. What I haven't seen addressed is that if climate change caused the herbivores to starve, their stomachs would have been relatively empty. Then the humans who depended on them would have potentially needed to overhunt to make up for the loss of nutrienst causing extinctions of animals they formerly lived in balance with, and then drove the development of systematic agriculture after the large herbivores were extinct.
cheers from Toronto love the channel 🦝
Not all impact events leave craters. If a field of objects the size of beach balls, many thousands of them, but with the total mass of say the Tunguska impactor entered the atmosphere and imploded the effect would be the same but there would be no crater. This is probably more common as iridium layers are more common as well in drill cores. Lots of unknown impact events.
Ever read Dennis Cox's work? I found it intriguing, especially from a reconnaissance damage assessor.
As a a geo(hydro)logist I do a lot of research in the Namurian-Dinantian-Famennian-Frasnian (Upper-Carboniferous to Middle-Devonian) transitions right now for the construction of a deep surface gravitational wave detector. We found some layers in our deep boreholes at the Dutch/Belgium/German border area that might be related to extinction events Hangenberg event et cetera. In case of young Dryas, I would take into account that we have not the full info of human occupation, the smoking gun of the impact(s) we found some of the fragments. The energy involved for the large meltwater pulse my impression is that the impact could be the major cause for the megafauna extinctions. It also causes unexpected challenges to large animals. The humans could have added to the extinction of the megafauna, in the end there was a world wide civilisation that was very well develloped before this YDB event and quite a bit less after this event.
We haven’t found any impactor fragments from YD period yet
@@gravitonthongs1363 one of the craters in South America there were some impact fields. The one at the US-Canadian border is not found due to the presence of the thick Laurentian ice-sheet. But geophysical data, local geology in combination with the calculated trajectories based on shapes and position of the Carolina bays et cetera point towards it. Oh and over here in Netherlands and Belgium we also found a layer containing iridium from that age.
@@br2v the iridium is just regular cosmic flux.
The Carolina bays are deflation hollows dated over a 100k year period. No geologist believes they are ejecta marks.
What is this other “geophysical data” you refer to?
@@gravitonthongs1363 there are anomalys found in the great lake area, using micro gravitation and geomagnetics. But a lot of survey work needs to be done over there. The people of the Dutch geological that worked on it, think that it triggered Volcanism in the Eifel ( Laacher See (Koblenz area Germany) < 50 miles from where I live) . Antonio Zamora and even NASA did some great research .
Sad we never got to see these magnificent animals. Thanks for the video.
great video, i enjoyed it 🙂
Forgot to mention: the Younger Dryas Impact Hypothesis suggests the comet broke into fragments, hit the Northern Hemisphere, emptied Lake Agassiz and Lake Missoula, left erratics all over Washington, and the Willamette Meteorite is likely a fragment from that comet which was carried toward Washington just like the erratics were. Jerry Kroth, Ph.D.
It shows no signs of fragmentation. It is just a meteorite.
Hm. A short answer is "The science doesn't know exactly so far." 🤔🙄 But at least we studied everything we could have get to 🤓
Thanks for the video, greetings to the cat 😌🐱
You should go on Joe Rogan with Graham Hancock
The Carolina Bays, as an artifact of secondary impacts (many) from an ice sheet impactor should be explored further. A very compelling body of evidence.
Stop spamming
@posticusmaximus1739 The only way to get the information out.
@@justmenotyou3151 *disinformation
@@justmenotyou3151 *disinformation
@@SayWhut276 not in this case.
Her analysis is very likely correct. The theory is a meteor impacted on the ice sheet that was melting, but still covering the Great Lake region or further north. Nor further south because the ice no longer covered regions a few hundred miles south of the Great Lakes. Causing the extinction of animals near the impact site, hence the extinction of the animals of the Americas, but not the rest of the world.
The problem with this is basic geography. The southern part of South America is a lot further from the alleged impact site than Europe. Yes, the animals that were further away, in southern South America became extinct while the animals much closer in Europe were not effected.
It seems the critical factor, in the sudden extinction of the American megafauna, was not the distance in miles from the Great Lakes region, but whether a human could reach a region on foot, for the first time, regardless whether it was one thousand miles away or six thousand miles away.
We need to look at the pattern of the extinction of megafauna as a whole, world wide. First disappearing in Eurasia and Australia, then later in the Americas. Basically, whenever expert hunters first suddenly appeared, the megafauna because extinct. A worldwide pattern that happened around the world. And continued into historical times when humans first showed up at islands. Modern humans arriving and extinctions go hand in hand.
The great exception is Africa. Why Africa? Well, humans did not become great hunters overnight. They gradually became better and better over time. And modern humans first developed modern behavior in Africa. Giving megafauna there enough time to gradually a more cautious behavior and keep away from upright animals that at a glance don't appear to be much of a concern. But everywhere else there were no modern hunters, then suddenly there were, causing pretty immediate extinction unless the mega fauna could undergo immediate evolution, which they could not.
Your videos are always informative, and the information is well presented. I would agree with you that there is not enough evidence of an impact from space causing the rapid cooling at the Younger Dryas (named after an alpine flower actually). However, some of the things like above average levels of iridium, microdiamonds and spherules, plus the dark mats, that occur over a certain area, but not worldwide, could indicate that rather than an impact, it may have been a series of airbursts. Think of the Tunguska event in 1908 in Siberia, which seems to have been an airburst rather than an impact. It was devastating over quite a large area of fortunately little human habitation. I also think that the main reason for the extinction of the megafauna was human hunting. Being an Aussie, the megafauna in Australia, such as the giant short faced kangaroo, and the diprotodon, declined and became extinct after the human migration to Australia some 65,000 years ago. They hung on until about the time of the warming 20,000 years ago. The climate in Australia became warmer and drier, and the human population was larger. The predators such as the thylacaleo, and the giant goanna megalania, declined at the same time. You don't need a global catastrophe to explain those extinctions.
Tell your cat I said hi. 👋
Would a single impact be able to cause > 1000 years of cooling anyway? If I recall correctly, the K-Pg impact winter is supposed to have only lasted a few decades, so (as a non-expert) I'd be surprised if a much smaller impact had caused much longer-lasting cooling. Or is the hypothesis about multiple impacts and/or different cooling mechanisms?
What are the odds that multiple asteroids all hit the same region over a thousand years? Honestly aliens seems more plausible
Melt water is the mover and shaker, but an impact added to the cooling.
@@justmenotyou3151 what?
Comparing the KPG event to the YDIH is like comparing a minor fender bender to a high speed, head on collision between semi-trucks. The former was magnitudes of degrees larger than the latter. The evidence suggests multiple impacts over the coarse of several thousand years by fragments of the disintegrating Comet Encke. Populations of various mega-fauna would have been diminished enough over those multiple events to ultimately lead to they're extinction. Not suddenly eradicated like the dinosaurs.
Excellent presentation, BUT... 1) the human arrival into the America's has been pushed back to at least 23,000 BP, and this is from a number of North and South American sites. So, the idea of overhunting, especially given the millions of megafauna all over the continent/s (think the bison population before the coming of Europeans) and relatively low population density of human hunters doesn't make this scenario seem very likely, 2) one of the problems with the analysis of the YDIH is that it is seen as a single massive event, and not a series of smaller, but still devastating impacts in the oceans, over the ice sheet and air bursts over land. You have done a superb job of analyzing the one scenario (single impact) but there are others that need this type of in-depth consideration. 3) the megafaunal extinctions would have been drawn out, given the main destruction of such impact/s would have been on ecological niches and habitats. The idea that the firestorm of such an impact would have killed off all the megafauna in one week (month?) doesn't ring true, where collapsing habitats does make more sense.
I could go on, and on and on... :-) but suffice it to say this has been an interest of mine for some time, and although I realize there are many problems with the YDI hypothesis, none of the other theories are "bullet-proof," at least not yet.
Good quality content 👍
Thank you.
I agree with you on "the topics of this video".
My point refers to the graph we first see at 1m 19s about the drastic temperature changes' during the ice ages.
Notice that the temperature climbs' are all strait lines with no dips in their rate of climb, unlike the temperature drops that are far more erratic.
Velancofsky (Probable mis spell?) was an A list academic travelling between Europe and the USA giving lectures from the 1910's on until he proposed that to cause an Ice age you first need a period of extreme heat. Seen in that light the difference between our current climatic era and the previos volatile one is not shown in how the last major ice age started but in the gentle way we came out of it.
Since "Save the Amazon" in the 70/80's I have been trying to convince people we are heading for global warming BUT there is one aspect that remains unknown; will the heating become "Run Away" or as Velancofsky proposed 'All that extra moisture in the atmosphere suddenly cools and fall as vast amounts of snow thus causing an Ice age to start with a bang.
I often quote an 'Ice Core' scientist I saw on a BBC documentary. while pointing at a two inch part of one of the cores.
"That is the start of the last Ice Age , that is one year or two, not three".
Interstellar debris fields could be a cause of many extinction events. it is not just one asteroid, but many small objects, not more than grains of sand, but so much of it, it would affect the sun, and occasional larger objects if unlucky. Deep debris field of sand would also give our skies a different color tone, while cooling, and other colors with more intense blue or red variations depending on simulation parameters. It is worth checking out and evaluate.
What about the Gothenburg magnetic excursion? The reason I state this is that there was another extinction event 42k years ago during the Laschamp excursion. It seems to line up with these extinctions.
Another great video! However I really thought it might cover the Pompeii trilobites.
I’m not taking a position on the YDIH, but I was alive in the 80’s and remember the KPH impact “theory” also being denied all over in the media and academia.
Yes, extraordinary theories require ample data, but…in the western world we tend to support free speech. And some people take advantage of this. Obstructionists and mischievous people are literally everywhere and cause trouble one daily basis.
These obstructionists were very busy in the 80s opposing the KPG event, as were the people claiming cigarettes don’t cause cancer!😅
Are we seeing that now? I am sure at least one group or person involved with the YDIH opposition is. Are all of them? Also not likely.
Extraordinary claims require axtraordinary evidence. Not just "ample" evidence.
Interesting how influencers like Rogan and Hancock can take a fringe theory and hyperpopularize it. I though fresh water dumping into the ocean and disrupting the AMOC was the most widely accepted theory but conspiracy theories seem to take precedence
Yeah its unfortunate especially since the combination of carbon dating optically stimulated luminescence and microfossil analysis from core samples show that Carolina bays do not have a single age like an impact would require instead having a broad minimum age distribution ranging over 100,000 years from pollen fossils matching MIS 5 (130,000 to 80,000 years) or OSL date of infill quartz sand deposits of ~109,000 years on the upper end to carbon dating giving minimum ages less than a thousand years. Likewise the range of infilling these bays have experienced varies from those still young enough to be lakes to ones which are entirely infilled and only discernable form their surroundings by their distinctive sandy soil and stratigraphic record.
How could a feature with an age distribution like that possibly be due to an impact? It doesn't make any sense!
@Dragrath1 a Rogan disciple told me it was a swarm of asteroids that pulled into Earth's and periodically impacted the Earth over 1,000s of years. I think there is a emotional desire for cool theories and people will make up the most outlandish things to support the cool theory.
@@Dragrath1 "Carolina bays do not have a single age like an impact would require ... It doesn't make any sense!"
Yes, it does.
If the impactor is was a fragmented comet orbiting around the solar system then parts of it could have struck the Earth on multiple occasions, as the comet returned to the vicinity of Earth. With a widely fragmented comet, some of the returns might miss the Earth completely, or only provide a light impact, whereas others would be more severe. The comparison in the video with the impact from the15km diameter end-Cretaceous asteroid impact is unhelpful, since nothing of that nature is posited for the YD.
If the Carolina bays were not caused by impact, as you suggest, how were they formed? They have every appearance of impacts caused by being struck a glancing blow.
Howdy Doc, I was wondering why your illustration showing the course of the melt water didn’t include the western, Scablands direction, so I googled it. Seems the onset of warming after the LGM was a variable period of warming and cooling. The Bølling Allerod, Older Dryas, addition warming, Younger Dryas wasn’t a smooth transition. Was the onset of warming relatively abrupt?
I'm guessing simplified illustration since the Pacific Ocean has a completely different circulation pattern, basically from being wider. Since Europe sticks out further west as it goes south, this interrupts and slows the gyre that should take place there, letting cold water build up in the north until it does sink. Then, when trade winds would normally cause upwelling a bit further south, Africa folds back east, letting water be drawn from a more equatorial area instead of being forced up from the bottom, further enhancing that slow northward flow in the Atlantic.
Excellent but your map of the AMOC appears backwards ... the warmer Gulf Stream portion should be next to North America
We are being fed a lot of goo about the AMOC. Suddenly it follows a different path than they had always told us. 🤔
@@soakupthesunman Imagine thinking an illustration whose aims are merely to show that there is a difference between warm (red) water and cool water circulation in the ocean, distributed around the globe, on a projection of a globe on a flat plane... is intended to be complete and in the perspective you want.
In reality, the global ocean circulation covers everything in the water. Anytime you see an arrow on the water it is merely to indicate to you some aspect, such as direction. This is analogous to drawing vector lines when trying to illustrate a field, such as a magnetic field.
Comet? they generally explode and don't leave a crater ie Tunguska event
How about "a mix of all of the above"? Sometimes, it sucks to be life on this planet, and that was one of those times.
thanks Dr geo girl
I don't think the impact caused the Younger Dryas, I think it's a coincidence. There seems to be evidence of multiple impacts over a period of tens of thousands of years prior to the Younger Dryas. The paper "Impact-related microspherules in Late Pleistocene Alaskan and Yukon “muck” deposits signify recurrent episodes of catastrophic emplacement" - Jonathan T. Hagstrum, et al., gives evidence of these prior impact events. If this paper is correct, then it seems likely that while a series of impacts did occur, they are not directly responsible for the Younger Dryas and associated extinctions. I think it is more likely that the Younger Dryas was inevitable, part of the natural processes at play, and that it is more likely that the Younger Dryas was the primary cause of these extinctions.
The microsperules are general cosmic flux
9:10 "dates just don't align".....a giant comet flyby, gets dismanteled.... and then some more stuff came in and also into the sun...so it would be a mix of CME's and Asteroïdes for while.
You make no sense
@@posticusmaximus1739 hi, usually someone who disagree will explain why it's not possible. ( i memt over many hundred years...) so the ENKI , meteor stream that crosses Earth's path twice a Year is BS? Thunguska is exacly is the dates and the direction is pretty accurate too... i'm vurious to know why you think it's not a plausable hypothesis.... ( sorry for my poor english ⚜️)
@@sacha11666 you do not make sense enough for me to agree/disagree with you
@@posticusmaximus1739 haha, this is rapidly twisting into a philosophical question. "If someone in your opinion makes no sense while emitting his idea on a presented subject, why reveling publicly your empty opinion but not doing the demonstation or explaining why when asked?
@@sacha11666 First you must learn proper English, right now it's all gibberish and bad grammar
About the AMOC, I can see why salty cold water should be sinking in the north Atlantic, water evaporates from the surface, taking away heat and concentrating salt, but why should water be upwelling in the Pacific and Indian oceans. This woud suggest that this water is somehow getting less salty and/or warmer, and I don't see why this should be happening in the depths. There would have to be some deep source of heat or fresh water..
This guy: www.youtube.com/@Antonio_Zamora ... he gets into this idea a LOT. Kinda made it sound like a modest impact hitting the ice sheet directly, causing a splash effect of smaller impacts (almost like flying shards of glacier) spread outward as far as the carolinas. Sounded interesting at the time the algorithm was putting it in front of me.
Aliens is a more compelling theory
I find aliens compelling,@@posticusmaximus1739, but I don't buy the premise.
I like your video .. Thanks ..
Cats are good people. And they have their own minds.
I watch for the science, but I stay for the Cat, more cat. Pip pip
She will be happy to hear this, thank you! ;D
Great video
You were all alone vocalizing for over a quarter of an hour, your kitty came to check on you.
I know that in my lifetime, I've been shocked by how much earth has regurgitated itself under my feet in regions I visited. This is due to the extreme gradualism we were taught.
That said, this would've no doubt been a very dynamically chaotic but beautiful age that none of us would want to be in lol
Love this channel.
So why isn't the younger dryas just part of the preceding cycles? It should be noted that there were other times when cooling took place subsequent to this.
Because we can tell that its timing did not match up with the periodicity of the Earth's astronomical (orbit, precession, & tilt) changes. The previous cycles were controled by these factors on their periodic timeline. That is why the Younger Dryas has warranted so much study because it didn't match up and thus, required some other cause(s). Sorry if I didn't make that clear in the video! ;)
Have you adressed the Carolina bays?
Hey Geo Girl, wanna see the whole and way more complex picture of the younger dryas impact? There is a crater, that caused the earth's crust shift, which led to the end of the ice age, the permafrost in Siberia, Alaska and Canada, and the extinction of the mammoths, that were frozen in ice alive in north of Russia. All that and many more I talk about in my presentation I worked on completely alone for 2 years, and published it just about 3 weeks ago! And yea, it's way more massive then people in the west are prepared to see. Regards, Anatoly
One thing to look at is: get that chart out for the entire last ice age. The same odd glitch in the temp chart can be seen at least three times before the Younger Dryas! 😮. It’s weird and I haven’t heard a good explanation for any of them. 😢. What did that the same way several times? …. The megafauna had over 8,000 years to adapt to humans and Clovis culture nearly disappeared at the same time of megafauna extinction. … The Carolina Bays are very curious 🎉
The draining of Lake Agassiz. Is a really interesting topic? From what I understand very little evidence of this major event exists because it probably occurred over Ice. The Ice Age Floods in the Pacific NW that have a lot of evidence display what a massive powerful event this was.
Hope Returns!
I don't remember ever hearing that the YDIH was ONE impact. The Carolina Bays come to mind.
They are deflation hollows formed over 100k years.
The Younger Dryas likely had very little to do with megafaunal extinctions seeing as similar fluctuations occurred during past interglacials as well, also as a result of ocean current disruptions, without killing off megafauna.
Maybe... The YD is still fairly unique in terms of its magnitude and abruptness of cooling. To date, we haven't documented an analogous event during past deglaciations. Add to that human expansion as an ecological pressure, and that climatic shift-even if previously experienced-becomes all the more potent on megafaunal populations.
@@ageofrocks
But we HAVE found evidence for such events in the interglacial before the current one.
@@bkjeong4302 To which one are you referring? Which interglacial?
@@ageofrocks
The one before this one.
@@bkjeong4302 So MIS-5e specifically? Not so much, at least not like the Younger Dryas. Better candidates are at the MIS-16/15 and possibly MIS-12/11 terminations, but we don't have any high-res constraints suggesting they were comparable in magnitude or abruptness of cooling. Only that there were analogous termination-ice surging events.
A friend of mine published about a Heinrich-analogous event at the stage 8/7e boundary, but likened it rather to H1 and H2-not the Younger Dryas.
Long story short, the YD is very unique as a climate anomaly, in magnitude, rate, and timing (very late in the deglaciation) in the context of the Late Pleistocene.
To "retreat" defined by Meriam: "An act of going away from something difficult, dangerous, or disagreable."
Glaciers DO NOT "retreat", they STAGNATE and MELT.
Just fundimental physics, and definitions. Important to a geologist.
If the most likely cause of the Youger Dryas was the disruption of AMOC by freshwater due to glacial melt, is there evidence that other post glaical warming periods were also followed by periods of post-glacial cooling, synonymous with the Younger Dryas?
Dansgaard-Oeschger events
It's hard to address such things comets generally do not leave impact craters . It may not have been anything other than a dust cloud passing through the solar system / as for the clovis people they survived ( imagine archaeologist always assume people of the past go extinct but we fail to understand that people of any time period are very smart and tenacious!
“Comets generally do not leave impact craters” …said no educated person.