Английская Википедия:Decorah crater
Шаблон:Short description Шаблон:Infobox terrestrial impact site The Decorah crater, also called the Decorah impact structure, is a possible impact crater located on the east side of the city of Decorah in Iowa, United States. It is thought to have been caused by a meteor about Шаблон:Convert wide which struck during the Middle Ordovician Period, circa 470 million years ago.
Description
Шаблон:Main The crater is estimated to be Шаблон:Convert in diameter, covered by the Winneshiek Shale.[1][2][3] There is no surface evidence of the impact, as the Winneshiek Shale is more than Шаблон:Convert below the bottom of the Upper Iowa River. The impact event, equivalent to 1,000 megatons of TNT,[2] did not appear to penetrate the Earth's mantle, but it did push down the underlying Ordovician and Cambrian bedrock several hundred feet.[4] It may be one of several Middle Ordovician meteors that fell roughly simultaneously 469 million years ago, part of a proposed Ordovician meteor event, including three confirmed impact craters: Rock Elm crater in Wisconsin, Slate Islands crater in Lake Superior, and Ames crater in Oklahoma.[5]
Pentecopterus decorahensis
The Middle Ordovician (Darriwilian) Winneshiek Lagerstätte sediments that filled in the crater contained a wide variety of unusual fauna. Among them was a newly discovered species of eurypterid, Pentecopterus decorahensis. Pentecopterus was scorpion-like in appearance, and the largest predator known from that time, measuring nearly 6 feet in length. Its species name was derived from "Decorah."[6]
See also
References
Шаблон:Impact cratering on Earth
- Английская Википедия
- Geology of Iowa
- Impact craters of the United States
- Landforms of Iowa
- Landforms of Winneshiek County, Iowa
- Ordovician impact craters
- Possible impact craters on Earth
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- Википедия
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