| 词条 | Decorah crater |
| 释义 |
| name = Decorah crater | other_name = | photo = Decorah crater.jpg | photo_size = | photo_alt = | photo_caption = Location of Decorah crater on bedrock map of Iowa | map = United States | map_alt = | map_caption = Location of the crater in the United States | map_size = | location = | label = | label_position = | coordinates = {{coord|43|18|50|N|91|46|20|W|region:US|display=inline,title}} | coordinates_ref = | confidence = Potential[1] | diameter = {{convert|3.5|mi|km|abbr=on}} | depth = | rise = | imp_size = | age = ~470 Ma Middle Ordovician | exposed = No | drilled = No | bolide = Ordovician meteor event? | translation = | language = | pronunciation = | topo = | access = | country = {{USA}} | state = Iowa | province = | district = Winneshiek | municipality = Decorah }} 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 meteorite about {{convert|200|m|ft}} wide which struck during the Middle Ordovician Period, circa 470 million years ago. Description{{main|Iowa geology}}The crater is estimated to be {{convert|3.5|mi|km}} in diameter, covered by the Winneshiek Shale.[2][3][4] There is no surface evidence of the impact, as the Winneshiek Shale is more than {{convert|50|ft|m}} below the bottom of the Upper Iowa River. The impact event, equivalent to 1,000 megatons of TNT,[3] did not appear to penetrate the Earth's mantle, but it did push down the underlying Ordovician and Cambrian bedrock several hundred feet.[5] 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.[6] Pentecopterus decorahensisThe 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."[7] {{multiple image|direction = horizontal |align= left |width1= 240 |width2= 240 |image1=USGS Decorah crater.jpg |image2=Middle Ordovician craters.jpg |caption1=U.S. Geological Survey aerial resistivity map of the Decorah, Iowa area, showing the Decorah Impact Structure. |caption2=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. }}{{Clear}} See also
References1. ^{{cite LSA |last=Mikheeva |first=Anna |year=2017 |title=The Complete Catalog of the Earth's Impact structures |url=http://labmpg.sscc.ru/impact/index1.html |publisher=Russian Academy of Sciences |pages=1 |accessdate=2017-10-14}} {{Impact cratering on Earth}}2. ^{{cite news|last=Vastag|first=Brian|title=Crater found in Iowa points to asteroid break-up 470 million years ago|url=https://www.washingtonpost.com/national/health-science/crater-found-in-iowa-points-to-asteroid-break-up-470-million-years-ago/2013/02/18/545131f8-76d5-11e2-aa12-e6cf1d31106b_story.html?wprss=rss_national|accessdate=19 February 2013|newspaper=Washington Post|date=18 February 2013}} 3. ^1 {{cite news|title=Geological survey: Ancient meteorite crater sits below Decorah|url=http://thegazette.com/2013/03/05/ancient-meteorite-crater-sits-below-decorah-geological-surveys-confirm/|accessdate=6 March 2013|newspaper=Cedar Rapids Gazette|date=5 March 2013}} 4. ^{{cite web|last=US Geological Survey|title=Iowa Meteorite Crater Confirmed|url=http://www.usgs.gov/newsroom/article.asp?ID=3521|accessdate=7 March 2013}} 5. ^{{cite web|last=Iowa Department of Natural Resources|title=GEOLOGIC MAPPING FOR WATER QUALITY PROJECTS IN THE UPPER IOWA RIVER WATERSHED|url=ftp://ftp.igsb.uiowa.edu/igspubs/pdf/TIS-54.pdf|work=Technical Information Series No. 54, 2011|accessdate=19 February 2013}}{{dead link|date=September 2017 |bot=InternetArchiveBot |fix-attempted=yes }} 6. ^{{cite journal|last=Heck|first=Philipp |author2=Birger Schmitz |author3=Heinrich Baur |author4=Alex N. Halliday |author5=Rainer Wieler |title=Fast delivery of meteorites to Earth after a major asteroid collision|journal=Nature|date=15 July 2004|volume=430|pages=323–325|url=http://www.nature.com/nature/journal/v430/n6997/abs/nature02736.html|issue=6997|doi=10.1038/nature02736|bibcode=2004Natur.430..323H|pmid=15254530}} 7. ^{{cite journal|last1=Lamsdell|first1=James C.|author2=Derek E. G. Briggs|author3=Huaibao P. Liu|author4=Brian J. Witzke|author5=Robert M. McKay|title=The oldest described eurypterid: a giant Middle Ordovician (Darriwilian) megalograptid from the Winneshiek Lagerstätte of Iowa|journal=BMC Evolutionary Biology|date=2015|volume=15|issue=169|url=http://www.biomedcentral.com/1471-2148/15/169|doi=10.1186/s12862-015-0443-9|pmid=26324341|pmc=4556007}} 6 : 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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