Iowa Warning: You are not logged in. Your IP address will be publicly visible if you make any edits. If you log in or create an account, your edits will be attributed to your username, along with other benefits.Anti-spam check. Do not fill this in! ===Geology and terrain=== [[File:Desoto Lake1.jpg|thumb|[[DeSoto Lake (Iowa)|DeSoto Lake]] at [[DeSoto National Wildlife Refuge]]]] [[File:Iowa terrain.jpg|thumb|Iowa terrain]] Iowa's bedrock geology generally decreases in age from east to west. In northwest Iowa, [[Cretaceous]] bedrock can be 74 million years old; in eastern Iowa [[Cambrian]] bedrock dates to c. 500 million years ago.<ref>{{cite book|last1=Prior |first1=Jean Cutler |others=Adapted from ''Iowa Geology 2007'', [[Iowa Department of Natural Resources]] |title=Geology of Iowa: Iowa's Earth History Shaped by Ice, Wind, Rivers, and Ancient Seas |url=http://www.igsb.uiowa.edu/Browse/geoiowa/GEOIOWA.HTM |access-date=August 9, 2009 |publisher=Iowa Department of Natural Resources Geological Survey |url-status=dead |archive-url=https://web.archive.org/web/20090416104106/http://www.igsb.uiowa.edu/browse/geoiowa/geoiowa.htm |archive-date=April 16, 2009 }}</ref> The oldest radiometrically dated bedrock in the state is the 2.9 billion year old [[Otter Creek Layered Mafic Complex]]. [[Precambrian]] rock is exposed only in the northwest of the state.<ref>{{cite book|last1=Anderson |first1=Wayne I. |title=Iowa's Geological Past: Three Billion Years of Change |date=1998 |location=Iowa City |publisher=University of Iowa Press|page=21 }}</ref> Iowa can be divided into eight [[landform]]s based on [[glaciation]], [[soil]]s, [[topography]], and river drainage.<ref name=Prior91>{{cite book|author=Prior, Jean C. |date=1991 |title=Landforms of Iowa |publisher=University of Iowa Press, Iowa City |url=http://www.igsb.uiowa.edu/Browse/landform.htm |url-status=dead |archive-url=https://web.archive.org/web/20090302084724/http://www.igsb.uiowa.edu/Browse/landform.htm |archive-date=March 2, 2009 }}</ref> [[Loess]] hills lie along the western border of the state, some of which are several hundred feet thick.<ref>{{cite web | url=http://pubs.usgs.gov/info/loess/ | title=Geology of the Loess Hills, Iowa | date=July 1999 | access-date=March 26, 2008 | publisher=[[United States Geological Survey]] | archive-date=March 28, 2008 | archive-url=https://web.archive.org/web/20080328103032/http://pubs.usgs.gov/info/loess/ | url-status=live }}</ref> Northeast Iowa along the [[Upper Mississippi River]] is part of the [[Driftless Area]], consisting of steep hills and valleys which appear as mountainous.<ref>{{cite web |url=http://www.uni.edu/iowaonline/prairievoices/images/Landforms_of_Iowa.pdf |title=Landforms of Iowa |publisher=Uni.edu |access-date=April 7, 2020 |archive-date=July 31, 2012 |archive-url=https://web.archive.org/web/20120731024555/http://www.uni.edu/iowaonline/prairievoices/images/Landforms_of_Iowa.pdf |url-status=live }}</ref> Several natural lakes exist, most notably [[Spirit Lake (Iowa)|Spirit Lake]], [[West Okoboji Lake]], and [[East Okoboji Lake]] in northwest Iowa (''see [[Iowa Great Lakes]]''). To the east lies [[Clear Lake (Iowa)|Clear Lake]]. Man-made lakes include Lake Odessa,<ref name=Odessa>{{cite web|url=http://www.iowadnr.com/fish/fishing/lakes/ode58.html |title=Odessa |publisher=Iowa Department of Natural Resources |access-date=June 6, 2009 |url-status=dead |archive-url=https://web.archive.org/web/20080921204808/http://www.iowadnr.com/fish/fishing/lakes/ode58.html |archive-date=September 21, 2008 }}</ref> [[Saylorville Lake]], [[Lake Red Rock (Des Moines River)|Lake Red Rock]], [[Coralville Lake]], Lake MacBride, and Rathbun Lake. Before European settlement, 4 to 6 million acres of the state was covered with wetlands, about 95% of these wetlands have been drained.<ref>{{Cite web|url=https://www.iowadnr.gov/environmental-protection/water-quality/water-monitoring/wetlands|title=Wetlands|website=Iowadnr.gov|access-date=April 7, 2020|archive-date=April 7, 2020|archive-url=https://web.archive.org/web/20200407181024/https://www.iowadnr.gov/environmental-protection/water-quality/water-monitoring/wetlands|url-status=live}}</ref> Summary: Please note that all contributions to Christianpedia may be edited, altered, or removed by other contributors. If you do not want your writing to be edited mercilessly, then do not submit it here. You are also promising us that you wrote this yourself, or copied it from a public domain or similar free resource (see Christianpedia:Copyrights for details). Do not submit copyrighted work without permission! Cancel Editing help (opens in new window) Discuss this page