Rock Elm Disturbance
The Rock Elm Disturbance is an impact crater in Wisconsin, United States, roughly 40 kilometers southwest of Menomonie.[1] The disturbance is named for Rock Elm, Wisconsin, a nearby community.
Features
The meteorite is estimated to have been 170 m (560 ft) in diameter with a mass of 9×109 kg (2.0×1010 lb) and impact velocity of 30 km/s (67,000 mph). The crater is 6 km (3.7 mi) in diameter, and fossils found in the rock filling the crater suggest it dates to the middle Ordovician Period, about 455 to 430 million years ago.[2] It may be one of several Middle Ordovician meteors that fell roughly simultaneously 469 million years ago, part of a proposed Ordovician meteor event that includes the Decorah crater in Iowa, the Slate Islands crater in Lake Superior, and the Ames crater in Oklahoma.[3]
Composition
Researchers discovered a rare mineral called reidite at the Rock Elm impact site. Reidite is a dense form of zircon (ZrSiO4),[4] and has been found in three other massive meteorite impacts.[4]
References
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External links
- Article from Geotimes.com, March 2004
- Press release from the University of Wisconsin-River Falls
- Craters in Wisconsin
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