Heart of Louisiana: Meteor Crater

Published: Dec. 20, 2011 at 12:58 AM CST|Updated: Jan. 11, 2013 at 3:30 PM CST
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A few miles south of Greensburg, there is a noticeable dip in the road as you drive along Louisiana Highway 37. But it doesn't seem out of place among the Gentle Hills of St. Helena Parish. Nothing seemed unusual until LSU scientists working for the Louisiana Geological Survey began mapping the area.

"And while we were looking at the topographic maps, we noticed a very strange circular feature," said scientist, Paul Heinrich.

This map, created with laser imaging, shows Highway 37 crossing the north end of that curious depression. This is the circle, more than a mile across, that caught the eye of Heinric.

"And since there are no volcanoes in Louisiana and there are no salt domes in this part of Louisiana, we knew that something strange was happening," said Heinrich.

The only explanation Heinric could come up with was a meteor crater. It likely happened within the last 10,000 to 12,000 years, which was a time when primitive people inhabited the piney woods of St. Helena.

A meteor would have struck without warning, perhaps on a moonlit night. A large space rock is speeding toward the Earth, and once it hits the friction of Earth's atmosphere, the fireball is only seconds from impact.

"It would have been a very bad day for anybody within 20 or 30 miles of here," said Heinrich, " Probably like a small nuclear explosion there would have been like a 10 or 20 mile zone in which anybody or anything here would have been either killed or very badly injured.

The meteor that made this crater was no small piece of cosmic rock. In fact, when it slammed into the Earth, it was at least 100 feet in diameter.

That's similar in size to the meteor that made this crater in Arizona. Heinric believes the Louisiana crater is slightly larger than this. But, erosion and weathering in Louisiana's soft soil have erased what was once a massive hole.

"This is a fracture here, this is a fracture and this is a fracture," explained Heinric.

Heinric has found evidence that proves his theory of a meteor strike. The impact fractured the iron-rich bedrock and superheated water bleached the sediment. Those fractures are clearly visible near the crater's rim. But the real proof is in tiny pieces of quartz, that have similar shock marks, microscopic dark lines that confirm the impact.

"The only known manner in which shocked quartz is formed is either by meteorite impacts or nuclear tests," said Heinric.

It's the finger print of a prehistoric catastrophe; the only known meteor crater in Louisiana and one of only 120 on Earth. And it's an example of how we can still make fascinating discoveries about our past.