Unexpected Find: Geology at Ground Zero

Laatste wijziging: zondag 12 april 2009 om 19:47, 2257 keer bekeken Print dit artikel Bekijk alle nieuws feeds van onze site
zondag 12 april 2009

(ice age geology revealed at ground zero)

This is actually something I know a little about! According to the article, crews working on the World Trade Center site have dug down pretty deep and uncovered glacial bedrock features caused 20,000 years ago - for example, a 40-foot pothole.

In order to start construction, the firm that’s working has to remove layers and layers of soil (which should be interesting in and of themselves!), and in doing so have exposed a ton of beautiful geology. Unfortunately for us, most of it has to be filled in, blasted, or otherwise destroyed in order to make way for Tower 4 of the new World Trade Center.

I can expand on this a little - in my junior year Mineralogy class (which MSU is re-running this year, awesome!), we took a trip to NYC to visit the American Museum of Natural History and check out their extensive mineral collection. We took a side trip after that, in the rain, to check out some of the geology in Central Park. There are some great exposed outcrops there, mostly of the Cambrian-age Manhattan Formation. These are fantastic crenulated schists and gneisses, and you can see glacial features like polished surfaces, striations, and grooves carved by dragging of rocks by the ice sheet. Though most of them have been removed, you can still find glacial erratics - rocks that were taken from other areas and dropped by the ice sheet as it melted - lying around.

These surfaces are also really great to see weathering rates, where the quartz-rich layers weather much slower than the others - quartz is harder, and therefore it takes longer to weather than its mica/feldspar counterparts. For more information, or to maybe take a geology field trip to New York City yourself, check out the USGS page! It’s quite informational.

Bron: geologist.com

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