Around four years ago, geologists that were part of a survey team took a look at some water well drill-cuttings, and found a unit of shale that was seen to be unique. The shale — a type of sedimentary rock composed of mud made of quartz, clay, and other tiny fragments of minerals — was located only underneath and around the city of Decorah, Iowa, and formed a circular basin with a width of around 3.4 miles. After some examination, shocked quartz — essentially a type of quartz with a different microscopic structure than regular quartz — was found in samples from the crater located below the shale. Shocked quartz is considered to be a likely result of an extraterrestrial impact. It’s nothing like Roswell, if that’s what you were thinking, but rather is a meteorite impact.Now, a new geological survey to examine mineral and water resources of the region have provided geologists with a chance to take a peek at the impact crater, which is estimated to be around 470 million years old.And the USGS representation:And finally the same area in Google Maps:The airborne survey used an electromagnetic system that can detect the level of electricity rocks are capable of conducting, as well as a system that can detect changes in rock density. With their powers combined, the survey systems were able to detect an area that is reported to be almost circular, that is unlike the surrounding region. The crater lies a few hundred meters below ground. Geologists will use this recently gathered data, combine it with drill samples, and attempt to suss out the meteorite’s impact energy and geometry.It’s fascinating that a town was built on top of an impact site. We’re still confirming, but this might be the most exciting news to come out of Iowa in the last 470 million years.