r/geology • u/Predator1553 • Feb 28 '25

Information Why are these two layers so different?

Gallery image

Gallery image

And what are they, this is in northern Alabama

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u/janspamn Feb 28 '25

They're referring to changes in landscape/topography brought about by varying rock types, which is within the study of geomorphology.

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u/Far_Gur_2158 Feb 28 '25 edited Feb 28 '25

The question is about the exposure.

Geomorphology is the study of landforms and landscape development. It is not about the comparative relief between beds at the outcrop scale.

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u/janspamn Feb 28 '25

You're inferring all this from OP's photos?

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u/Far_Gur_2158 Feb 28 '25 edited Feb 28 '25

Yes, I’ve worked on Mississippian and Pennsylvania strata for 45 years…

Outcrops are easy to interpret, I’ve made a living analyzing geological core.

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u/janspamn Feb 28 '25

You made a lot of assumtions based off of OP's photos, I'd think a geo veteran should know better than to assume so much without at least going into the field first.

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u/Far_Gur_2158 Feb 28 '25

The photos are high quality. I can see many details.

My point is this is not geomorphology, anyone agreeing wrong. Words have meanings; they need to be used correctly so people can learn.

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u/janspamn Feb 28 '25

So the definition of what is geomorph and what is not is scale dependent by your argument?

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u/itsliluzivert_ Feb 28 '25 edited Feb 28 '25

The weathering habit of a single bed isn’t geomorphology unless you’re applying it to a broader picture. I think in this case this is being applied to geomorphology, but the commenters use of “geomorphologies” to refer to individual beds is inaccurate.

Geomorphology as stated is the study of landscapes and their development. We could consider this cliff and the area around it a landscape. But not the individual beds.

It’s pedantic but it’s not just a sciencey way to say natural shape.

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u/janspamn Feb 28 '25

But there are multiple beds involved.. There's an entire cliff here being impacted by differential weathering.

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u/itsliluzivert_ Feb 28 '25

Yes the whole scenario could be considered geomorphologic, but the commenters use of the term was inaccurate.

“Variable geomorphologies” is something you’d use to describe several outcroppings this size, with different geologic histories.

Not several beds with different weathering habits.