Did You Know!
🌽 Rare Iowa Fact: A Giant Impact Crater Is Hidden Beneath the State
One of Iowa’s most fascinating secrets is something you could drive right over without ever knowing it exists. Beneath the area around Manson, Iowa, lies an enormous buried impact crater known as the Manson Impact Structure.
Scientists believe a large asteroid or comet slammed into what is now Iowa roughly 74 million years ago, when dinosaurs still roamed North America. The collision was incredibly powerful and created a crater approximately 22 miles wide, making it one of the largest known impact structures in the United States.
Today, however, you won’t find a giant crater when visiting Manson. Millions of years of geological activity, sediment accumulation, erosion, and glacial movement eventually buried and obscured the structure, leaving little indication at the surface of the violent event that occurred there.
The crater became especially interesting to scientists because researchers once considered whether the Manson impact might have been connected to the mass extinction that wiped out the non-avian dinosaurs. Later research determined that the Iowa collision occurred millions of years before the famous Chicxulub impact associated with the extinction event about 66 million years ago.
That means Iowa was struck by a major space object long before the dinosaurs disappeared—and evidence of that ancient collision remains hidden beneath the state’s farmland today.
Fun takeaway: Someone traveling through north-central Iowa can essentially pass over the remains of a gigantic prehistoric impact crater without seeing anything unusual at all.