The 22-Mile Impact Crater in the Middle of Iowa

Welcome to Iowa; home of the Hawkeyes, Cyclones, and the biggest meteor impact crater in the U.S.

When this rock hit West-Central Iowa, it leveled nearly everything within a two hundred-mile radius. But it also provided some unexpected lasting benefits to the area.

Get our free mobile app

How Long Ago Did This Happen?

The giant Meteor struck the area around what is now Manson, Iowa way back during the Cretaceous Period, approximately 74 million years ago. It killed nearly everything within around 250 square miles of its impact, however, it was not a mass extinction event. That would come around 8 million years later. Sorry, Dinosaurs.

How Big Is The Crater?

The crater is an astonishing 22 miles wide and nearly three thousand feet deep. Before it made landfall, the meteor was over 1.5 miles wide in space. As it entered Earth's atmosphere, it was traveling at an astonishing 38,000 mph.

It wasn't discovered until 1959, because it was long ago buried in over 100 feet of sediment, due to glacial retreat.

Did Iowa Look Different Back Then?

You bet it did. In fact, much of western Iowa was covered in a large inland sea. So was South Dakota, Nebraska, North Dakota, and part of western Minnesota.

How Did This Effect The Water?

The impact incinerated all the limestone rock in the region, which is why this part of Iowa still has soft water to this very day. The rest of the state has hard water, because the limestone there was left in tact.

For a full look at the asteroid's impact on the region, check out this fantastic new YouTube video from Geology Hub.