Thursday, October 30, 2008

Fluvial Systems

Hearing the word Fluvial should incite one of three reactions: you get really excited, you yawn, or you look confused. That's just the way it works. I happen to really enjoy studying fluvial systems, though anything too extensive can really bore me.
Here's a shot of the Snake River from Henry's fork. Notice the classic cut-bank and point bar deposition; it's about as good of an example of a meandering river as you could hope to find.
Here's a shot of the Snake River at the south fork.
Sedimentary structures near the south fork which are worth looking at

Tuff Stuff; more of the Kilgore

For another day-trip, we went out to the Ririe Reservoir dugway again. I managed to make it home without any significant ash fragments in my eye. These photos show more of the detail of the Kilgore tuff deposits. As seen in the photo above, these are very thick ash deposits.

We used Jacob's staffs to measure thickness of the different ash deposits.

So much pumice!

Another contact further up.

An "intraclast" (the brownish clast just below the pen). Clasts of the underlying bed are included in the subsequent depositional unit, in this case, a "rip up" clast.

Friday, October 24, 2008

Eolian Deposits

These are the St. Anthony sand dunes near Rexburg. They are lateral dunes at the flank of a mountain. I was surprised at the immensity and hieght of some of the hills. There is a shallow interdune lake near the edge of the dunes. The whole thing seemed a little surreal -it's something I've never seen before.
The shallow lake was full of ripple marks.
You can see the Tetons off in the distance.

Monday, October 20, 2008

Huckleberry, Kilgore, and Blacktail

This is a tuff post. Get used to corny puns -they are a significant element in communication in all the best geologic social circles.

At the nose of this outcrop, the Huckleberry Ridge tuff is exposed in the upper layers (above the darker flow layer, the Kilgore vitrophyre)

The Kilgore tuff vitrophyre shows displacement along a fault; typical of caldera rim zones.

Spectacular columnar jointing of the very thick Blacktail tuff (though the picture didn't turn out quite as spectacular)

More faulting -this reminds me of a GEOLOGY 101 textbook figure.

These sites are along the dugway near Ririe Reservoir in Idaho.

Wednesday, October 15, 2008

Faults and Folds

Over conference weekend, I spent part of Sunday afternoon at my roommate's house in Lake Point, Utah. The view from his front yard was spectacular; thanks to a wildfire last year sometime, the mountainside is an array of exposed faulted and folded beds. I'm not certain which fault system these are associated with -I'm looking into it. These photos show the different orientation in strata. If I had more time, I would've liked to have taken a closer look. But that's life.
I survived my exam in my structural geology class this week, and got my grade from my intro. to field methods class. I'm pretty pleased with it all. Now, if I can pass my mineral ID exam in my minerology class on Monday, and I feel pretty confident I will, I'll be satisfied.

Wednesday, October 8, 2008


Ah, the Tetons. Aren't they grand?

There isn't really a photo to accompany this one. Now that I've stated that, I realize that maybe I should've taken one. Regret gets me nowhere.
Our Mieralogy/Petrology group went out to the Ririe Reservoir dugway last Thursday to study some ash-flow units.
I wasn't really all that prepared for the trip -after some catch-up work in the lab, I just "showed up" at the scheduled departure time.
Well, to be brief, I had no eye protection, and I ended up having a wind-blown pumice fragment caught in my eye-lid. My eye was irritated, red, sore, and watering. I knew better than to rub it; silicate materials can scratch your cornea.
After working out insurance details with the accountants at the school, I made a visit to the local eye-doctor. He inverted my upper eye-lid, found the fragment, and removed it with a cotton swab.
I had been trained from my earliest days in Geology to always wear eye-protection in the field. I realize the importance of this rule now.
A few people in the class weren't able to come on the trip, and so I'm heading back to the site tomorrow afternoon to help supplement what they've missed. This time, I'll be taking my camera, a water bottle, and, of course, some eye-protection.
Now that I've gone and told the story, maybe I'll throw in a pretty picture -just for the sake of enjoying the blessing of good vision. OK, so maybe I'll throw in a picture of the culprit, just to make my peace; here it is -pumice.

After looking at that picture in detail, I realized that my rock hammer bears the reminder: wear eye protection. A good rule of thumb, not just for hammer use.

Monday, October 6, 2008

Mr. Hansen, pick a category.

I'll take rocks that won't support a dam thing, Alex.
The Teton dam never even officially opened. It failed before the opening ceremony. What could've prevented this blunder? A little bit of GEOLOGY.

Curved joints -not a good sign of a stable rock body.

Wednesday, October 1, 2008

Wind River Canyon, Wyoming

Even if you don't really care about rocks, the different units are worth seeing.
Chugwater Formation

Dinwoody Formation

Phosphoria Formation

Tensleep Sandstone

(top to bottom)Amsden Formation, Madison Formation (Mission Canyon Limestone), Bighorn Dolomite, Gallatin Formation, Gros Ventre Formation, and Flathead Sandstone.

Another exposure of the Great Precambrian/Cambrian unconformity: Precambrian granite and Flathead Sandstone