Huge Impact Crater Found in Remote Congo - Expedition Had Brushes W/ Snakes, Poachers


Victoria Jaggard
National Geographic News
Published March 8, 2011

A circular depression deep in the Democratic Republic of the Congo (DRC) has been confirmed as the first known impact crater in central Africa, a new study says. The find brings the number of known meteor craters on Earth to 182.

The so-called Luizi structure was first described in a German geological report from 1919. But without further fieldwork, it was impossible to say for sure that the 10.5-mile-wide (17-kilometer-wide) feature had been made by a meteor impact.

On other planets, such as Mercury and Mars, it's easier to identify impact craters based only on their shapes, since these worlds no longer have geologic forces making major changes to their surfaces.

But on Earth, many older craters have likely been erased by tectonic activity or erosion, while others are so covered with dense vegetation or sediments, like Luizi, that they're almost impossible to spot without satellites.

What's more, the crater-like structures we do see may have been made by volcanoes, collapsed underground chambers, and other forces that have nothing to do with impacts, said study leader Ludovic Ferrière, curator of the rock collection at the Natural History Museum of Vienna in Austria.

"On Earth, to confirm it's an impact, you have to go in the field because you need evidence of high pressures and temperatures," Ferrière said.

Crater Expedition Had Brushes With Snakes, Poachers

The researcher first became interested in the Luizi structure after seeing satellite pictures published in the 1990s.

By studying the available satellite data, Ferrière and colleagues estimated that the structure has an elevated rim about 1,148 feet (350 meters) high, as well as an interior ring and a central depression.

But to truly confirm Luizi as an impact crater, the researchers had to mount an expedition to the politically tumultuous DRC.

"I was working for a year just to find a contact there, because you need a local person to help you find your way around," Ferrière said.

With funding from the National Geographic Society/Waitt Foundation program, Ferrière—then a postdoc at the University of Western Ontario in Canada—visited the crater site in June 2010 with colleagues from the University of Lubumbashi. (The National Geographic Society owns National Geographic News.)

"I flew direct to Lubumbashi, the second largest city in the DRC. From there we had to drive from the city to the crater," he said.

"I had looked at maps and planned a route before I left. But when I got there, my contact told me there is no bridge across part of my intended path. We had to take some crazy gravel roads with big potholes inside. These are not good roads to drive on, even with a four-wheel-drive car."

The team set up camp in a small village about 8 miles (13 kilometers) from the crater rim, recruiting two local guides/porters and a soldier to help them safely navigate the wild terrain.

"The crater is in a national park, and I thought it would be like the jungles of South America," Ferrière said. "Instead it was a tree savanna—a big plataeu with dry grass. The grass was sometimes more than a meter [3.2 feet] high."

Standing on the rim of the Luizi structure, Ferrière could see skinny trees that seemed to fill the depression, with the crater's distant edge rising like small hills.

Despite the remote, wooded terrain, "we saw no large animals, only snakes. But we did see a lot of remnants of poachers. Sometimes we'd come to a site and the doused fires were still hot."

Congo Rocks Had a Shock

Ferrière's team spent about a week at the crater collecting samples, which were sent back to the lab in Canada for analysis.

"I found so-called shatter cones, which are features in the rock only found in impact structures," he said. The nested, conical shapes in such features are evidence that the bedrock has been exposed to extreme pressure from a shock wave.

The crater rocks also contained an abundance of shocked quartz, a version of the mineral known to form only from impacts or nuclear blasts, Ferrière said.

"Everybody will believe me now, I think, that this is an impact site."

The scientists think the Luizi crater was made by a meteor more than 0.6 mile (a kilometer) wide that slammed into what is now the DRC at about 45,000 miles (72,000 kilometers) an hour.

For now it's unclear how old the crater is—the scientists can say only that the affected rocks are about 575 million years old, "but we know it's younger than that, because the rocks have been excavated," Ferrière said.

"It would be nice to do more fieldwork, because the shape of the structure with this inner ring can tell us about the exact formation process involved," he added. In the meantime, the researcher will continue to study the rock samples, now housed at the Vienna museum.

"There is still a lot to discover" about Luizi, he said.

The Congo-crater research will be presented March 8 at the 42nd Lunar and Planetary Science Conference in The Woodlands, Texas.

Well, at least he discovered that there are a lot big potholes in the DRC. Of course, I could have told him that before he went.

meteorite crater - that is something else invented by al gore, way back when

@Wink: If you ever find yourself in one of these craters, keep an eye out for meteorite fragments. They are incredibly valuable to collectors.

There is a program on US television called Meteorite Men, where these guys travel around the world hunting fragments with metal detectors. I was amazed to find out how valuable they were.

A few days of searching with a metal detector could pay for all or most of the cost of your safari.

Up here in Canuckistan, meteorites have been determined to be potentially dangerous. Parliament has therefore enacted legislation which bans them from impacting the earth. They are subject to huge fines and confiscation unless they can show documentation proving that they fell before the current laws came into effect. Pre-ban meteorites are grandfathered, but are legally bound not to leave the planet and then fall back again.

I feel much safer.

quote:

Originally posted by Wink:
Well, at least he discovered that there are a lot big potholes in the DRC. Of course, I could have told him that before he went.

Funny.

quote:

Originally posted by jwm:
Up here in Canuckistan, meteorites have been determined to be potentially dangerous. Parliament has therefore enacted legislation which bans them from impacting the earth. They are subject to huge fines and confiscation unless they can show documentation proving that they fell before the current laws came into effect. Pre-ban meteorites are grandfathered, but are legally bound not to leave the planet and then fall back again.

I feel much safer.

God bless them for lifting such a worrisome burden from our shoulders!