2018/12/10

Interpreting Geology in Tennessee

I was recently asked "How does one tell the difference in the limestone without a degree in geology?" This is a wonderful question. Below I will share some of my methods, and look at how effective those methods are at understanding the landscape.

As a geographer, my go-to for most things is to look at a map. I collect data and organize it and add to and improve it over time. This gives me an advantage, but it need not be exclusively mine. First in order to explore the data, you'll need some tools. This sort of analysis is appropriate for a desktop computer or laptop, not so much a cell phone operation as most cell phones can't hold and display data necessary to convey meaningful descriptions.
Geology Panel, Fentress and Pickett Counties, Tennessee
The first tool I recommend getting is Google Earth Pro. This is free, and can be downloaded here:
https://www.google.com/earth/versions/#download-pro

Install Google Earth Pro after you have downloaded it. It will associate files with the extension .kml and .kmz to open in Google Earth Pro when you double-click on them. You'll need to find some kmls now to display in Google Earth Pro.

Go to the link below to download the Tennessee statewide geology layer. Look for the link to tngeol.kmz.
https://mrdata.usgs.gov/geology/state/state.php?state=TN

Once you've downloaded this, double click the file and it should open in Google Earth. This geologic layer was created at 1:250,000 scale, so it is only marginally accurate when you're looking closely. It is great for creating at state wide scale, but not so good at looking at things up close.

For up close features, I use geologic maps at 1:24,000 scale, which are more than 10x as accurate. This data has unfortunately not publicly available until now. I make no promises as to the quality or accuracy of this (it does have errors), and it is an incomplete layer. Click here to download Tennessee State Geology 1:24k (incomplete; 344mb).

Making the connection from understanding the geology, to interpreting the landscape and understanding where interesting landforms are at is the next leap. I picked up most of these skills listening to other cavers and walking around looking for cave entrances. Along the way I figured some patterns out in regard to the distribution of waterfalls and natural arches.

These patterns are better described in other blog posts here:
Tennessee's Eastern Highland Rim - Part 1 - Geology
Tennessee's Eastern Highland Rim - Part 2 - Geography
Tennessee's Cumberland Plateau
Fort Payne Formation & Chattanooga Shale Contact Waterfalls
KTAG - Cave Density Map

I regard the next few links as incomplete. It's part of a project I've been working on to flesh out specific strata within the Mississippian strata of the Eastern Highland Rim. Here are links to a few (partially finished) reports:
Tennessee Mississippian Strata: Pennington Formation
Tennessee Mississippian Strata - Fossils - Bangor limestone
Tennessee Mississippian Strata - Fossils - Hartselle sandstone & Monteagle limestone

If you want to get real serious into map reading and interpretation check this blog post out. It's more than geology, and requires more complicated tools to develop and interpret, but it is accessible to the public:
Lidar Map of Sparta, Tennessee

This is a lot of data. The data alone is no substitute for spending time looking at things. Take the time to match up familiar features with their specific geology. Check your hunches with more seasoned geographers, geologists, and naturalists.