Rock Elm Disturbance

Rock Elm Disturbance
North American Middle Ordovician impact craters, which may be part of the Ordovician meteor event. Key: 1: Ames crater, 2: Decorah crater, 3: Rock Elm Disturbance, 4: Slate Islands crater
Impact crater/structure
Confidence Confirmed
Diameter 6 km (3.7 mi)
Age 430-455 Ma
Middle Ordovician
Exposed -
Drilled -
Bolide type Ordovician meteor event?
Location
Coordinates 44°43′N 92°14′W / 44.717°N 92.233°W / 44.717; -92.233Coordinates: 44°43′N 92°14′W / 44.717°N 92.233°W / 44.717; -92.233
Country  United States
State Wisconsin
District Pierce County
Municipality Rock Elm
Location of the crater in the United States

The Rock Elm Disturbance is an impact crater in Wisconsin, United States, roughly 40 kilometres (25 mi) southwest of Menomonie.[1] The disturbance is named for Rock Elm, Wisconsin, a nearby community.

Description

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) and has been found in three other massive meteorite impacts.[4]

References

  1. ↑ "Rock Elm". Earth Impact Database. University of New Brunswick. Retrieved 2017-10-14.
  2. ↑ Peters, Christopher William, Middleton, Michael D., & Cordua, William S. (2002). "Paleontology of the Rock Elm Disturbance". Abstracts with Programs - Geological Society of America. 34 (2): 95.
  3. ↑ Vastag, Brian (18 February 2013). "Crater found in Iowa points to asteroid break-up 470 million years ago". Washington Post. Retrieved 19 February 2013.
  4. ↑ Oskin, Becky (November 3, 2014). "Rare Mineral Discovered in Ancient Meteorite Impact Crater". Live Science. Retrieved 2015-02-17.


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