Let’s start at the very beginning. Not the beginning of time, mind you. Just the beginning of our journey. We will start in Indiana, since that’s where I’ve lived all my life, and that’s where my geologic curiosity started. Today I had my first meeting with an expert. Walt Gray is the educational outreach coordinator for the Indiana Geological Survey. We met in his office on the campus of Indiana University. Because I am a graduate of Purdue University (IU’s big rival, for readers outside of Indiana), I was a little reluctant to travel to Bloomington for the visit. Evan and Kieran accompanied me, and Evan constantly made comments about how beautiful the rolling hills were in southern Indiana, and how spectacular IU’s campus is. He is considering attending IU next fall to study physics, much to my dismay. I’d reply, “Yes, southern Indiana is beautiful and yes, IU’s campus is amazing, but wouldn’t you like to go to the school Mom went to?!” Sigh. The boy has a mind of his own. Although I am a die-hard Boilermaker, I must admit, Indiana University is an excellent institution, and I’ll be very proud if Evan decides to go there.
Actually, it is fitting that the Indiana Geological Survey is located in southern Indiana, because the topography of that region is much more interesting, and there are far more road cuts in which the geological layers can easily be seen. Central and Northern Indiana, where we live and where Purdue is located are in a region that saw significant glacial action in the last ice age. Much of this region has been scraped flat by the glaciers, which left mixed sediment there as they receded. The bedrock is just not as obvious there. Also, I don’t think that IU could possibly be covered with more Indiana limestone than it already is! It does seem to be a great place to house the IGS.
When Walt and I started talking, I said something along the lines of, “I don’t have a ton of questions, just… could you tell me the entire geologic history of Indiana?” That’s not much to ask, right? As I’ve been reading John McPhee’s Annals of the Former World I’ve come to understand the Big Picture of geology a little better, so I really enjoyed Walt’s description of the history of Indiana. Years ago, I had learned that the bedrock in Indiana is mostly limestone which was created when Indiana was the floor of a shallow sea. This is why the fossils I always find in the creek beds near home are crinoid disks (parts of filter feeding marine animals similar to modern sea lillies), brachiopods (which look like clams with a dent in their shells), and parts of sponges… no dinosaur bones (although Kieran always asks). What Walt helped me understand was how all of this developed. We talked through the history, then made a short video with his explanation of how the stratigraphic column of Indiana’s rock tells the story of Indiana’s voyage from Pangea, when it was South of the equator and the north end of the state was pointed east; to it’s current location. My students always tell me it’s easy to understand how to solve chemistry problems when they watch me do it, but hard to understand on their own. In the same way, I found it easy to understand Indiana’s geology while Walt explained it. I certainly would not have pieced it all together from the reading I’ve been doing, although I feel like the reading has helped me get a good foundation, and I highly recommend McPhee’s book to anyone interested.
Here is a link to the video. It might have been longer, but I accidentally left a soccer game or two on the camera, so I didn’t have as much space as I would have liked. The video starts with a couple of clips of Walt explaining a bedrock map of Indiana and the stratigraphic column. Then, he demonstrated the reaction of several different forms of calcium carbonate rock with hydrochloric acid. At the end, there is a quick clip (I was running out of space on the camera) of fossil skulls of animals that lived in Indiana during the ice age. We start with a peccary, then a sabre-toothed cat, then a dire wolf. The last two fossils are molar teeth from a mammoth and a mastodon. I would like to have more time to make it all smooth with a title slide and nice fades between clips, etc. I’m a little nervous sharing this, as I’m a bit intimidated by both my weak video skills and the geology itself. But I have a great deal of packing and reading and to-do list checking to do right now, so this rough video will have to suffice. I tend to get bogged down with details as it is. I hope to have time when I get back home to clean things up a bit. Maybe one day I’ll have all my little videos “branded” with my own style of title slides and stuff, or maybe life will get in the way again. Well, without further ado, here it is… Video #1 in the series: https://www.youtube.com/watch?v=PAHS_2tci2A
Things I learned today:
- Limestone forms in situations where corals and other filter feeders thrive: shallow, warm salt water that must be free of sediment influx. If the water is clouded with too much sediment, the filter feeders take in too much sand or silt and not enough food, so they die off. Geologists refer to periods of time that meet this criteria as the “carbonate factory” being turned on, because these filter feeding animals make calcium carbonate or calcium magnesium carbonate shells out of dissolved minerals in the water. When they die, their shells get buried, then compacted into stone
- Indiana’s shale and sandstone come from periods when Indiana’s shallow sea was getting a lot of sedimentary matter that ran off the land at higher elevation (the Appalachian range and/or from higher ground in Canada). During these times, the carbonate factory was turned off.
- Indiana’s geology has been shaped by plate tectonics, despite the fact that the area is not currently very seismically active. Pangea formed due to plate collisions. The North American plate collided with several continental plates, including those of Eurasia and Africa. These collisions bent and folded the North American plate and pushed the Appalachians upward. If you look at the eastern US on a map with satellite view, the wrinkles are really clear!
- When the Appalachians were being built, two bowl-shaped basins formed near the edges of the wrinkles. One is centered on southern Illinois and Indiana, the other is centered on Michigan. Indiana’s rock layers were bent as these two areas dipped down, and the rock between them was pushed up. This explains why older rock is near the surface in the southeastern part of the state, while younger rock is exposed to the southwest and northeast.
- “Indiana limestone” is really just the Salem limestone. Much of the limestone in the state does not make for great building material, but the Salem limestone does. This stone has been used for many federal buildings across the US, a great number of buildings in Indiana, and even the Empire State Building.
- Always clear the camera before doing an interview, so there’s plenty of space!
- And lots more!
After the interview, the boys and I ate lunch with Michelle and her son David. Evan and David are both seniors this year, and it was nice to see them together again. They’ve known each other since they were babies, but with all of their extracurricular activities, they rarely get together anymore. It was great to talk to them about their futures and how their junior years went. We enjoyed some Indian food at a restaurant on the square called Bombay Cafe. I’m going to have to work out a way to explain to ethnic restaurant owners that Kieran likes all kinds of food and handles spicy food better than most six year olds. They always suggest that he won’t like this or that item. He and I shared a veggie combo plate and he ate nearly all of the medium-spicy dal. That’s OK… more paneer for me! The paneer is their signature dish, and all you kiddos going (back) to IU next year, you NEED to go try it. It’s amazing. I guess I have a reason to look forward to going back to IU again!