Manson crater facts for kids
Manson impact location shown in red on bedrock map of Iowa
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| Impact crater/structure | |
|---|---|
| Confidence | Confirmed |
| Diameter | 35 km (22 mi) |
| Age | 73.8 ± 0.3 Ma Late Cretaceous |
| Exposed | No |
| Drilled | Yes |
| Bolide type | Chondrite |
| Location | |
| Coordinates | 42°35′N 94°33′W / 42.583°N 94.550°W |
| Country | United States |
| State | Iowa |
| Municipality | Manson |
 Location in the United States
Location in Iowa
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The Manson crater is a huge hole in the ground, but it's hidden! It's located near Manson, Iowa. This giant crater was made when a space rock, like an asteroid or a comet, crashed into Earth. This happened about 74 million years ago, during the time of the Cretaceous Period. That's when dinosaurs were still around! It was one of the biggest space rock impacts ever in North America. For a while, people thought this impact might have caused the dinosaurs to disappear. But scientists later found out it happened too long ago for that.
Contents
Discovering the Hidden Crater
You can't see the Manson crater on the surface today. That's because it's covered by layers of dirt and rocks left behind by glaciers. The land above it now looks completely flat.
How Scientists Found It
Even though it's hidden, scientists found clues about the crater. In 1912, people drilling water wells found strange, broken rocks deep underground. These rocks looked like they had been crushed and melted.
In 1955, scientists started studying this unusual area. At first, they thought it might be from a type of volcano explosion. But later, in 1959, a scientist named Robert S. Dietz suggested it was from an impact.
Proof of an Impact
More proof came in 1966 from Nicholas Short. He found special quartz grains in the rocks. These grains looked like they had been "shocked" by a huge, sudden force. This was strong evidence that a space rock had crashed there.
Dating the Crater
In the early 1990s, scientists did more detailed research. They wanted to see if the Manson crater was linked to the event that wiped out the dinosaurs. They used a special method to find the age of the rocks from the crater. They found the crater was about 74 million years old. This meant it happened about 10 million years before the dinosaurs disappeared. So, the Manson impact wasn't the cause of their extinction.
What Happened During the Impact
The space rock that hit Earth to create the Manson crater was likely a stony meteorite. It was huge, about 2 kilometers (1.2 miles) wide!
The Impact Site
At the time of the impact, this part of Iowa was very different. It was the shore of a shallow inland sea called the Western Interior Seaway. The impact was so powerful it broke through many layers of rock. It hit ancient granite and shale rocks deep underground. It also smashed through younger sedimentary rock layers.
A Unique Effect
One interesting thing the impact did was vaporize some limestone layers. These layers usually make water "hard" in other parts of Iowa. But because they were destroyed in the Manson area, the water there is now unusually "soft."
Images for kids
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Extent of the Manson impact structure, showing how big it is underground.
