Monday, January 30, 2012

Cambrian Steak

Finaly aged for 500 million years

A few of my friends have these little stuffed-animal trilobites, either finding them online or buying at Geological Society of America meetings. Anyway, I think they're pretty great. Who doesn't love trilobites?

Wednesday, January 25, 2012

Midwest Aerial Geomorph

Over this last Thanksgiving I had the chance to fly back home to Minnesota. Something I really like to do is look at the landscapes through the airplane window (when I get a window seat). Although the midwest doesn't have much topography to look at, there is plenty of geomorphology to keep a geoscience-educated person entertained, along with some meteorology and infrastructure. I happened to have my camera onhand, something I'll try and remember to do more.

Shot of Springfield-Branson National Airport (KSGF) after takeoff

A limestone quarry outside of Springfield. Makes you realize how much limestone there is in this state!

Just making sure the wing is still attached. Yep!

Looks to be some kind of weather front, clear on one side, cloudy on the other.

Again, the weather front. I like this shot because it was difficult to see the land on the clear side due to scattering, so it looked blue, making this shot look like we're flying over the edge of Antarctica, a flight I would love to take someday.

Begin the fluvial geomorphology! A stream with some good meander-bends. Most geologic events take places over millions of years, so sometimes it's a nice break to think about meandering streams which are very dynamic (geologically speaking)
You also don't realize how close clouds are to the ground sometimes until you see them from above.
Excellent example of a dendritic pattern stream in the light-colored farm square. It looks so sharp and clean probably due to the farmer plowing and planting right up to the stream bank, removing any kind of riparian zone. Although this maximizes growing land for the farmer this leads to more soil and fertilizers getting washed into the stream, a major problem in the midwest contributing to the Golf Dead Zone.

Saw these wind farms and knew I wasn't in Missouri aymore - Wind farms are common in Iowa, Minnesota, and Illinois, but are slow to start up in Missouri (I've heard some fairly negative political radio ads about wind farms here)

Lake Thunderbird in Illinois, a neat little water body I saw which turns out to be a reservoir. You can also really see where the smaller tributary valleys are where the dark heavy vegetation has been left untouched within the plowed lighter colored cropland.

I used to live next to the Mississippi River in my undergrad days, so part of me will always have a thing for large rivers and small river towns. This turned out to be the town of Hennepin, Illinois.

A larger river town. You can definitely see the industrial district along the river. I also liked the little airport just outside of town. I wonder how long until the city envelopes it? This is the cities of Peru and La Salle, Illinois

The cities of Peru and La Salle, Illinois, as above, but with the winding river in view. I wonder why the city doesn't develop into that meander point?
Sorry for the strange angle of the shot, but I wanted to get as much of this in view as possible to see all the little sandbar islands along the river. Getting into the heavily urbanized regions of Illinois.

A shot for the physicists. I saw this and didn't believe what I was looking at at first, but yes, that is Fermilab outside of Chicago.

Wednesday, January 18, 2012

Missouri AAPG Trip - Bennett Spring, Decaturville Impact, Ha Ha Tonka

The local American Association of Petroleum Geologists (AAPG) hosted a trip to check out some interesting Missouri geology. Destinations for this trip included (in order of appearance here on in) Bennett Spring, the Decaturville Impact Structure, and Ha Ha Tonka State Park.

Our first stop was in Bennett Springs State Park.
This is the location of the 4th largest spring in Missouri, putting out about 100 million gallons per day (or about 150 cubic feet per second for those of you that are used to spring discharge in cfs). In comparison the springs I study around Springfield are usually less than 10 cfs. This spring flows from a conduit in the Gasconade Dolomite. Divers have descended down into this conduit for almost 200 feet before it was too small or flow was too great to continue.

If karst hydrology isn’t your thing, this place is a big fishing spot. Even in mid-January people were fly-fishing all throughout the park (ok, it was actually about 70 degrees outside still). I love fly fishing, so I’ll have to come back out here sometime with my gear.

This was all possible due to the trout hatchery on site which keeps the spring-fed river stocked with delicious catchable fish.

Because we are geologists, while enjoying the scenery from one of the bridges which crosses the river we all had to stop and look at the rocks which made up the bridge. One of the notable rock units was a rippled sandstone (the Roubidoux Sandstone), a local rock unit.
In one of the more obvious blocks we could see the ripples were nice and asymmetrical, while also being upside down (due to the rounded “crests” of the ripples, which are actually the troughs). I also took the opportunity to be creative with my hand lens.

Our next stop was to head to the Decaturville Impact Structure. This crater is a few miles wide and is only noticed in satellite imagery or by noting the unique structures in the sedimentary rocks (which are otherwise quite flat-lying in Missouri).

This crater is both recognized by its ring-shaped topographic signature…

The first roadcut is what most people refer to when they discuss the unique rock structures of the Decaturville Impact structure. Most people that study the rocks around Missouri know most of the sedimentary rocks here are basically horizontal. Structures, such as anticlines (at least obvious ones), tend to be rare. Here we see that the rocks are sometimes horizontal, then suddenly tilted, faulted, and folded at times.
Slightly dipping rocks.

Slightly more dipping rocks

Hinge of the anticline

More tilting rocks

Our fearless leader, demonstrating the thrust fault

Drag fold in the thrust fault (illustration below)

Much of the rocks have been heavily brecciated, almost to the point that referring to the in their original name and age is meaningless (geologic maps call some of these the Gasconade Dolomite, but it should really be said that the Gasconade is just the parent rock).
Breccia with large chert clasts

More breccia. Here, a layer of rock (gray) is broken and rounded at the edges

Clasts of granite were said to be found in the breccia, although we didn't spot any

Many of the clasts have been cored for paleomagnetics testing.

Large clast with paleomag boreholes, also in the surrounding matrix

More paleomag boreholes in this deformed layer
We drove further north into the impact structure and looked at some more breccias in the rocks.
Large clasts in the breccia

Strangely enough, large clasts of shale which now weather out giving the rock a porous appearance. How do you get football-sized clasts of loose, yet intact, shale?

Calcite vug

A strange sigmoidal feature with a clast in the center

Our third spot was to check out the "caprock" in the impact structure (assumed to be due to its undeformed nature while being in the center of the crater). It was a quartz sandstone-conglomerate, white to orange.

Checking out the sandstone/conglomerate

Some places are fairly mature but it gets coarse in some areas

Shot of one of the more mature spots through the hand lens

This sandstone was very sparkly

Some spots were very conglomeritic

After leaving the crater we had lunch and headed to Ha Ha Tonka State Park.

The first part of this spot involved visiting the "castle". At the park is the remains of a sort of castle-home built by Robert McClure Snyder from the early 1900s.

Little background story behind the ruins

A series of trails around the castle structure also provided some nice views of the steep valley where the spring is located in. We first explored the ruins, then went down into the valley.

This is the water tower to provide water to the castle

View of the castle from the river

Pointing off into the distance. Also, it was very windy

Map of the park. The photo above was taken at the red star.

Another map of the park with trails. We walked on most of the trails.

The spring, from above

The spring, again.

Spring-fed river

Some background of the spring. My favorite part was the name of the spring, Ha Ha Tonka, which translates to "laughing waters" by the Osage Indians. I found this fun because this same language is used a lot in names from my home state of Minnesota (Ha Ha, such as Minnehaha Falls in the Twin Cities, and Tonka is just everywhere in Minnesota, home of Tonka Toys, and my hometown of Minnetonka). All these words (haha, minne, tonka, sota, etc) can be combined to form a lot of words.

As explained by Wikipedia... "The word Minnesota comes from the Dakota name for the Minnesota River: Mnisota. The root mni (also spelled mini or minne) means, "water". Mnisota can be translated as sky-tinted water or somewhat clouded water. Native Americans demonstrated the name to early settlers by dropping milk into water and calling it mnisota. Many locations in the state have similar names, such as Minnehaha Falls ("waterfall"), Minneiska ("white water"), Minneota ("much water"), Minnetonka ("big water"), Minnetrista ("crooked water"), and Minneapolis, which is a combination of mni and polis, the Greek word for "city".

Illustration of the geology of the park. It was explained to be a very large collapsed cave/solution feature

The cliffs of insanity!

A natural bridge down in one of the sinkholes

Got back home while the sun was setting. Long day!