Buried deeply within Iowa's bedrock, the Midcontinent Rift System can be seen clearly in magnetic anomaly maps of Iowa.
This is a billion-year-old tectonic plate scar that extends from Kansas through Lake Superior. No major active fault lines exist in Iowa, and Iowa is one of the most seismically stable states in the U. With the exception of the 1968 Illinois earthquake which caused the water tower at Lineville to leak, no injuries or significant damage has ever been caused by earthquakes in Iowa.
In Iowa, the eastern border of the Missouri Plains is the Loess Hills, forming steep rounded bluffs. S., surface water in Iowa is never safe to drink untreated, contamination by agricultural runoff including nitrates, herbicides, pesticides, and animal waste is common.
Although glaciation has erased all surface evidence of the impact, the bedrock associated with this impact is unique in Iowa.Highly eroded, leaving stark, beautiful "golden hills".Northeast Iowa is covered with eroded Pre-Illinoian till with moderate loess formation, frequently in the form of paha ridges, muted relief except for steep rolling hills near river valleys, and deeper valleys.Iowa's bedrock geology generally increases in age from west to east. 74 million years old, in eastern Iowa Cambrian bedrock dates to ca. Seventy-four million years ago, a large asteroid crashed into what is now southeast Pocahontas county creating the Manson crater.Probably a mile in diameter, it would have killed most animals within 650 miles, roughly an area from modern Denver to Detroit.They consist of grey to pink cobbles within limestone that when cut or smashed open reveal a hollow crystal-filled interior.Geodes are common around Geode State Park in Henry County.Occasional small earthquakes occur near Fremont County in the far southwest, and the Sioux City area can occasionally be shaken by nearby tremblors.Large earthquakes associated with the New Madrid Fault of far southern Illinois and Missouri can occasionally be felt in eastern Iowa.The aquifer has dropped by as much as 300 feet since the 19th century, resulting in dry wells, the disappearance of natural surface springs, and the diminishment of water quality. In general, soils of southern, eastern, and western Iowa are loess-derived, while soils of northern and central Iowa are till-derived.Most level areas of Iowa have soils highly suitable for agriculture, making Iowa one of the most productive farming regions of the world.