Geological Maps - recognising folds

An introduction to folds on maps - using William Smith’s 1815 original and the State Geologic Map of Pennsylvania. We'll see how to spot folds and then to trace them out - gaining understanding of how rock layers project into the subsurface - and how they continued above ground before being partially eroded away! Part of "The Shear Zone" video channel. Copies of the maps are available on the Shear Zone website (see link from Channel home page).

[@DarthCalculus]

I live in southeast Pennsylvania, and last summer took a trip to the northeast corner of the state. It was a stunning view the entire time. Much of the highway that cuts through the mountains is surrounded by exposed rock faces. I teach a middle school earth science class and it was very helpful inspiration

[@robbutler2095]

Thanks for the comment. I've not actually visited this part of Appalachia - but the State geo-team have done a fantastic job putting this map together and making it available. Lots of other info on their web pages - well worth a look.

[@JesstheGeologist]

Fabulous video! I study the structural geology of the southern Appalachians(mostly working in North Carolina), so it was nice to see your example from Pennsylvania. Anyhow, thanks for the crystal clear explanation!

[@robbutler2095]

Thanks - glad you enjoyed it! It's a great map....

[@joek81981]

Hey, I was in Flight Sim 2020 and I was wondering what on earth caused all that mess in Pennsylvania. I wasn't expecting to understand the answer I'd get, but that was easy. I thought maybe tons and tons of little rivers and streams. That was my guess before I watched this video. Good stuff.

[@robbutler2095]

glad to be of help. hope the flight was good too!

[@douglasjerolmack4450]

Hugely helpful for a geomorphologist that is trying to start learning about structures. Thanks!

[@robbutler2095]

I'm glad it's useful for you. You could also check out the video on "Folds and folding - description" (you'll need to scroll down through the main listing of videos on the channel)... as this looks at examples of structures imaged on GoogleEarth from the Zagros.... enjoy!

[@shahanamammadova5346]

Thank you for such a useful video!

[@robbutler2095]

Thanks - there are a few others on my geological maps playlist.... if this is what you're after.

[@illumencouk]

We've only been watching for a few minutes but can anybody tell me why the 'law of superposition' is flawed.

[@shahanamammadova5346]

I assume it can be flawed due to polarity criteria

[@illumencouk]

@@shahanamammadova5346Good morning. Thanks for engaging and replying to the question I posed. Before I address your answer can I first ensure we're on the same page as the term 'Superposition' is a phrase most commonly associated with particle physics, and shouldn't be confused with the 'First Law of Geology', where, 'Superposition' states that the surface layer MUST be the youngest. If the top layer dates say 100,000 years, then this 'Law' states that every layer below this start date, MUST be older and so they date everything as such. I believe I can show with very good reason why this is in fact, unsound. Having explained a little more about the issue, Is it still off interest to you?

[@张宏远-z8t]

Folds are ductile structures and are not easy to be projected in map view. I would like to watch several times as an un-English learner.

[@robbutler2095]

There's a very long tradition of projecting folds from hillsides to maps and vice versa - it's how knowledge of Alpine structure was built for example by Heim, Staub etc.... Much depends on assumptions of cylindricity but - at least in the Alps - it does work as an approximation (tested by forecasting the structure in adjacent valleys)...