Alligator-back Formation: I’m Glad I Asked

A shale-like rock in the Blue Ridge: What's going on?

Why do the rocks at 3200 feet at the “very edge” of the Blue Ridge look as if they were laid down by water, layer after layer, when it is from harder, igneous rock that this geological province is formed (at least in my limited understanding?) Horizontally-layered dark mica-flecked rocks jut out across the ridge-tops like the vertical ridges along an alligator’s tail. What’s with that?

I asked a friend who asked a friend who knows, and who explained it nicely in his reply. I think he’d approve of it’s use for educational purposes. I know I learned something!

It’s detailed. I imagine eyes crossing. But for some nerdy types like me, this was immensely informative. Still not interested? Okay. You’ve forced me to talk dirty: metamorphic schist. So there.

I’ve put it up on my posterous page, just click the link.

Reblog this post [with Zemanta]
Share this with your friends!

Fred First holds masters degrees in Vertebrate Zoology and physical therapy, and has been a biology teacher and physical therapist by profession. He moved to southwest Virginia in 1975 and to Floyd County in 1997. He maintains a daily photo-blog, broadcasts essays on the Roanoke NPR station, and contributes regular columns for the Floyd Press and Roanoke's Star Sentinel. His two non-fiction books, Slow Road Home and his recent What We Hold in Our Hands, celebrate the riches that we possess in our families and communities, our natural bounty, social capital and Appalachian cultures old and new. He has served on the Jacksonville Center Board of Directors and is newly active in the Sustain Floyd organization. He lives in northeastern Floyd County on the headwaters of the Roanoke River.

Articles: 3013


Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

  1. The entire area I live in is underlain by metamorphic schist. Some of it contains large garnets in beautiful blue-gray layers. And you are right, it was a very interesting process that formed this wonderful metamorphic rock.