Middlesboro is a small town in the Cumberland Gap of southern Kentucky. About 300 million years ago, it was the bullseye for a cosmic missile: a small asteroid that gouged an impact crater about four miles wide. Evidence of that high-speed collision is preserved in the rocks below Middlesboro.

Middlesboro is one of about 30 confirmed impact sites in the United States. Most craters have been erased by wind, rain, and the motions of Earth’s crust. And many of the remaining ones aren’t visible — the only traces are found far below the surface.

The best preserved is Barringer Crater in Arizona. It formed about 50,000 years ago. It’s less than a mile wide, but it’s easy to identify as an impact crater. In fact, it’s the first confirmed impact structure on Earth. It helped geologists determine that most of the craters on the Moon were formed by collisions instead of volcanoes.

The largest American crater is Chesapeake Bay. It’s about 55 miles in diameter, and formed about 35 million years ago.

A few craters are easily accessible — you can drive through them. Examples include Middlesboro, as well as Crooked Creek and Decaturville in Missouri.

One of the easiest to see as a crater is Sierra Madera, in West Texas. It’s about eight miles across. A state highway crosses it, climbing over the northern rim, then passing near its central mountain peak — the scar of a collision almost a hundred million years ago.

Script by Damond Benningfield

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