Craters of the Moon, National Monument

On the way back from my weekend in Boise, we stopped at Craters of the Moon, National Monument. Craters of the moon is an extensive series of basalt flows produced by a fissure eruption -part of the Snake River Plain volcanics. The flow is fairly recent, in a geological sense: 8 eruptive events over the past 15,000 years. The basalt flows of Craters of the Moon differ from other extrusive snake rvier plain volcanics in compositional and textural variety. It's an impressive sight -especially as you drive through and realize the extent of the flows (It's quite large).

Menan Buttes

I helped lead a group of students on a field trip to the Menan Buttes last week. The weather was a lot nicer than the last tour I led and the group of students was awesome. They all seemed pretty fascinated and had a lot of good questions.
Xenoliths ("foreign rocks") within the basaltic tuff:
Topographic map of the Buttes. We climb the North Butte, the younger and larger of the two.
A profile of the Buttes from the BYU-Idaho campus

Explanation

The rock man has been on the road. And when I haven't been gone, I've been studying hard-core, or spending time socializing.
So if you have been disappointed in my lack of content, I'm sorry. One day I'll post something amazing, and it will have been worth the wait.

Photomicrographs

The BYU-Idaho Geology Department recently acquired a new digital camera and software for creating digital images of what you see through the lenses of a microscope. These are called "photomicrographs". These first few were slides of thin-sections of rock we use in our crystallography lab. I haven't got all the details worked out for mounting the camera and getting the optimal lighting conditions, but BYU-Idaho now has the capability to produce these things. And I'm the one who gets to figure out the details. It's exciting!

Garnet, Staurolite, and other Miscellaneous Schist

Yesterday, my friend and I went to Henry's Lake near Island Park, Idaho, just west of Yellowstone. The alluvial fans along the north shore's mountain front are rich with metamorphic mineral and rock samples.
This road-cut is a prime garnet-collecting site.
Here's a sample of the variety of metamorphosed pelitic rock present at this site.
Here's the road-cut that contains abundant staurolite (from the Greek "Stauros" meaning "cross") samples.
There was also a good amount of tremolite present at both sites.

Fossil Mountain

Fossil Mountain lies in the Southern end of the confusion range. In the photo above, the Eureka "quartzite" (in reality, a sandstone) tops the sequence, The Crystal Peak dolomite (the gray strata), the Watson Ranch "quartzite" (also a sandstone), then the Lehman Fm, Kanosh shale, Juab limestone, and Wah Wah limestone (I had fun saying that name).
Listric normal faulting has rotated strata, then a younger volcanic system emplaced the horizontal lava flows above (an angular unconformity).
Our instructor, Forest Gahn discusses stratigraphy and correlation of units across the valley. The Eureka unit near the top of the sequence lies at the valley floor and dips toward us: evidence of listric normal faults. Fossils found at this site: nautiloids, orthid brachiopods, gastropods, crinoids, ostrocodes, and sparse trilobites (typically fragmented); fauna of the Early Ordivician.
Surficial layers of sandstone units are bioturbated (burrowed), another indication of transgressive sea level.

U-Dig Trilobite Quarry

The U-Dig Trilobite Quarry is located in Western Utah, 34 miles north of Delta. The carbonaceous shale at the quarry is part of the Wheeler Formation.
I brought home abundant samples. Shown in the photo above are Asaphiscus and Elrathia. I also have some small samples of Perenopsis and the inarticualte brachipod, Acrotreta; all index fossils of the M. Cambrian.