Massive meteorite crater found in Canadian Arctic

LiveScience.com – Wed, Aug 8, 2012 University of Saskatchewan, Brian Pratt - A river gorge cut into the tundra of northwestern Victoria Island shows steeply tilted sedimentary rock strata. These deformed beds represent the central uplift caused …more Researchers in Canada's western Arctic have found evidence of a crater that formed when a huge meteorite slammed into Earth millions of years ago. Measuring about 15 miles (25 kilometers) across, the formation was named the Prince Albert impact crater after the peninsula where it was discovered. Researchers don't know exactly when it was created, but evidence suggests the crater is between 130 million and 350 million years old, according to a statement from the University of Saskatchewan. Meteors are fragments of asteroids or comets that enter Earth's atmosphere at high speeds; most are small, some as tiny as a grain of sand, so they disintegrate in the air, and only rarely are they large enough to make it to Earth's surface. When meteors slam into Earth, they are called meteorites. A team of geologists spotted this newly identified meteorite crater while surveying the region for possible energy and mineral resources. They were initially intrigued by steeply tilted strata visible in river gorges and other features in the flat tundra of northwestern Victoria Island. [Photos: Prince Albert Impact Crater] "Unless you recognized the telltale clues, you wouldn't know what you were looking at," researcher Brian Pratt explained in the statement. "You might see a bunch of broken rocks and wonder how they got there, but we found abundant shatter cones." Shatter cones are surface features with distinctive wavy patterns that are known to be created only by the tremendous force of a meteorite impact or an underground nuclear explosion. What's more, Pratt said his map showed that the feature is circular, which is characteristic of impact craters. "Impact craters like this give us clues into how the Earth's crust is recycled and the speed of erosion, and may be implicated in episodes of widespread extinction of animals in the geological past," Pratt said. "It's an exciting discovery." There are about 180 known impact craters on Earth. Geologists think they would find countless more if plate shifting, volcanic activity and erosion didn't hide the evidence of most ancient impacts. Earlier this summer, researchers in Greenland documented possibly the oldest and largest meteorite crater ever found on Earth. The crater, estimated to be 3 billion years old, currently measures about 62 miles (100 km) across. But the researchers believe its width before erosion was likely more than 310 miles (500 km) — much bigger than the largest visible crater, the 2-billion-year-old Vredefort crater in South Africa, which measures 186 miles (300 km) across.