Glacial erosion, continental collision, and more

avenne — Fri, 25 Jun 2021 20:26:22 +0000

Glacial erosion, continental collision, and more Alfred J. Venne Friday, 6/25/2021, at 4:26 PM

Tuttle Hill is a drumlin, a streamlined north-south elongated hill that formed when glaciers covered the Amherst region. Since they are usually elongated in the direction of glacier flow, geologists use drumlins to understand past glacial environments. They are often composed of unconsolidated glacial till, which you can see in the Geological Evidence for Glaciation exhibit at the Beneski Museum of Natural History, along with other ice age features of our local landscape.

If you look east from Tuttle Hill, you will see the Pelham Hills with a skyline of a flat-topped hill. These mountains formed during a series of mountain-building events that started approximately 450 million years ago and lasted until about 290 million years ago, when ancestral North America subducted beneath the margin of a colliding landmass. Continental collision thickened the Earth’s crust, creating high mountain ranges like the Himalayas today. This folded and buried existing rocks, exposing them to high pressures and temperatures. Growth of minerals like biotite, garnet, chlorite, staurolite, kyanite, and sillimanite in these rocks was part of the metamorphic process. From these minerals, we can infer that the depth of burial exceeded 20 kilometers and the temperature of metamorphism was as high as 700 degrees Celsius. In the Mountain Building in the Paleozoic exhibit in the Beneski Museum, you can find examples of different rocks formed at different depths and temperatures.

avenne — Fri, 25 Jun 2021 20:30:15 +0000

Alfred J. Venne Friday, 6/25/2021, at 4:30 PM

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Amherst College: 503 and 504 - Drumlins and Mountain Building

Glacial erosion, continental collision, and more