 | ||
The Rock Elm Disturbance is an impact crater in Wisconsin, United States, roughly 40 kilometers southwest of Menomonie. The disturbance is named for Rock Elm, Wisconsin, a nearby community.
Contents
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. 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.
Composition
Researchers discovered a rare mineral called reidite at the Rock Elm impact site. Reidite is a dense form of zircon (ZrSiO4), and has been found in three other massive meteorite impacts.