Archive for April, 2012

Wooster Geologists: Communicating New Knowledge

April 7th, 2012

AMHERST, MA – Congratulations to Wooster Geology Seniors Katharine and Andrew for their excellent presentations at today’s Keck Symposium! Andrew presented the results of his remote sensing investigation of channels on Ascraeus Mons on Mars. Andrew compared his channels to those on Pavonis Mons and in Hawaii. He characterized his channels as volcanic in origin based on their spatial distribution, surface stratigraphy, and geomorphological relationships.

Andrew poses by his poster during a rare quiet moment at the poster session.

Katharine presented her study of the Hrafnfjordur central volcano in the West Fjords of northwest Iceland. She found a complicated sequence of eruptive units that includes pyroclastic material, basalt, andesite, and dacite. Using geochemistry, Katharine determined that the units fall on different, genetically unrelated trends, suggesting that the Hrafnfjordur central volcano has a complex magmatic history.

Katharine enthusiastically explains her study to a thoughtful listener.

Overall, the Keck students are truly a motivated and talented bunch. It’s amazing to see what these students have accomplished over the course of a year. The symposium is not only a celebration of their achievements, it’s a powerful moment in which these students officially become part of the Keck alumni family.

The 2011-2012 Wooster Keck alumni.

Field Trip Friday

April 6th, 2012

AMHERST, MA – If you were following our adventures last summer, you’ll remember that Wooster helped lead a 6-student Keck trip to the West Fjords in northwest Iceland. You may not know that we also had a Wooster presence on the Keck Mars project. Now, after nearly a year of hard work, all of the Keck students are coming together at the Keck Symposium to share their findings and celebrate their accomplishments. This year, we’re at Amherst College in Massachusetts. The symposium kicked off today with glorious weather and a local field trip featuring “The ABV’s of Valley Geology: Arkose, Bedrock, and Varves.”

Our first stop was in the Moretown Formation. These early Paleozoic rocks were originally deposited on the edge of the continent and were subsequently deformed during the Taconic and (perhaps) the Acadian Orogenies. The outcrop consisted of interbedded schist and quartzite that had been metamorphosed to upper greenschist – lower amphibolite facies. We observed tight folds that showed fantastic crenulation cleavage, which developed as a result of multiple folding events.

Side-view of the crenulation cleavage, almost looking down the cleavage crenulation hinge.

The light reflects off of the wavy surface of micaceous schist layers. The pen is nearly aligned with the cleavage crenulation hinge.

Garnet porphyroblasts in the Moretown Formation.

After a brief stop at the Yankee Candle Company (what’s not to like about hot coffee, clean restrooms, and plentiful scented candles?), we made our way to Mt. Sugarloaf. Here, we visited the type locality for the Triassic Sugarloaf Arkose, a feldspar-rich sandstone and matrix-supported conglomerate. The arkose was deposited in the Deerfield rift basin during the opening of the Atlantic. Abundant orthoclase suggests that the sediment was close to its source. Most of the sediment was deposited by debris flows, but there is some evidence for reworking by a braided stream system.

Conglomeratic section of the Sugarloaf arkose.

We hiked to the top of Mt. Sugarloaf for a scenic lunch stop, where we had a breathtaking view of the Mesozoic rift valley in which the Sugarloaf arkose was deposited.

View from the top of Mt. Sugarloaf.

After lunch, we traveled back to 15,000 years ago, when the rift valley was filled with proglacial lake Hitchcock. The lake was over 200 km long, stretching from upstate Vermont to central Connecticut. Seasonal layers of silt and clay were deposited on the lake bottom, forming varves. It’s the flat-lying varves that make the valley floor so flat. The annual layers were also critical in the development of the New England Varve Chronology, which suggest that the lake existed for over 4,000 years.

Lake Hitchcock varves.

Close-up view of the annual layers in the Lake Hitchcock varves.

Our last stop of the day was to see the trace fossil Eubrontes (aka dinosaur footprints). The three-toed tracks are subparallel. If the tracks are the same age, then they may have recorded a passing herd. If the tracks are on different bedding planes, then this area may have been on a migration route. The Amherst College Beneski Museum of Natural History hosts the largest collection of dinosaur tracks world, primarily collected by Edward Hitchcock (also of the proglacial lake, third president of Amherst College, 1845-1854).

Three-toed dinosaur footprint. Do you see it?

It was nice of the dinosaurs to outline their footprints in chalk to make it easier for us to see!

We finished the evening with a reception at the museum (a drool-worthy collection that will be the focus of a future post). After a quick pizza dinner, the Iceland group is meeting for the last time to work on tomorrow’s presentations. It’s a bittersweet meeting; it’s fun to bring everyone together to compare findings and pat ourselves on our backs for a job well done, but it’s a bit sad to know that our Keck experience is coming to an end.

The Iceland crew on the Keck Field Trip.

Collaborative (and sticky) Inquiry in the Geology of Natural Hazards

April 3rd, 2012

Wooster, OH – Today’s hazards class was devoted to lava viscosity. Viscosity plays an important role in controlling how volcanoes behave, from determining how quickly magma ascends to whether the eruption will be explosive or effusive. In Hazards, we’ve been discussing the factors that control lava viscosity, like silica content, volatiles, and temperature. Although we’d love to experiment on real lava, like the folks up at Syracuse University, we just don’t have the right set up. Instead, I borrowed Ben Edwards’ (Dickinson College) idea of using corn syrup. (I’m not the only one).

We simulated lavas of different viscosities by varying the temperature of the corn syrup and adding rice and sand. Then, we poured our “lava” down ramps and timed how fast they moved. We used their velocities to calculate viscosity and compared our results to real lava.

 

We also blew bubbles into our “lavas” to simulate volatiles.

Wooster’s Fossil of the Week: A spiriferinid brachiopod (Logan Formation, Lower Carboniferous, Ohio)

April 1st, 2012

This brachiopod is one of the most common in the Logan Formation of Wooster, Ohio, so our students know it well from outcrops in Spangler Park and the occasional excavations in town. Four specimens of Syringothyris Winchell 1863 are visible in the slab above. The critter in the upper left is an earlier Fossil of the Week: the bivalve Aviculopecten subcardiformis. This suite of fossils is about 345 million years old (Osagean Series of the Lower Carboniferous).
We can’t identify the species of these Logan Formation brachiopods because the original shells dissolved away long ago. We are left with the sediment that filled the insides of the shells, producing what paleontologists call internal molds. Syringothyris belongs to the Order Spiriferinida, a group of elongate brachiopods that are punctate, meaning there are tiny holes penetrating their shells. Unfortunately this is one feature I can’t show you with internal molds!
Alexander Winchell (1824-1891) named and first described the genus Syringothyris. He was a geology professor at the University of Michigan for decades, specializing in Lower Carboniferous stratigraphy and paleontology. He was also the state geologist of Michigan. Winchell was one of the early American Darwinists, working hard to reconcile religion and science in the United States (with decidedly mixed results!).

References:

Bork, K.B. and Malcuit, R.J. 1979. Paleoenvironments of the Cuyahoga and Logan Formations (Mississippian) of central Ohio. Geological Society of America Bulletin 90: 89–113.

Winchell, A. 1863. Descriptions of FOSSILS from the Yellow Sandstones lying beneath the “Burlington Limestone,” at Burlington, Iowa. Academy of Natural Sciences of Philadelphia, Proceedings, Ser. 2, vol. 7: 2-25.

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