Killer Crater.Last April, geologists sleuthed out an impact crater “Meteor crater” redirects here. For the crater of that name, see Meteor Crater. In the broadest sense, the term impact crater can be applied to any depression, natural or manmade, resulting from the high velocity impact of a projectile with larger body. , or massive depression, buried under hundreds of feet of rock in Woodleigh, Australia. The hidden 121 kilometer (75 mile)-wide crater crater, circular, bowl-shaped depression on the earth's surface. (For a discussion of lunar craters, see moon.) Simple craters are bowl-shaped with a raised outer rim. Complex craters have a raised central peak surrounded by a trough and a fractured rim. could solve an age-old question: What caused the biggest mass extinction mass extinction, the extinction of a large percentage of the earth's species, opening ecological niches for other species to fill. There have been at least ten such events. in Earth's history? Scientists think an asteroid (large space rock) smashed into our planet's surface 247 million years ago, destroying 90 percent of all life at the time, and producing the massive Woodleigh crater Woodleigh is a large meteorite crater in Western Australia, centered on Woodleigh Station east of Shark Bay. A team of four scientists at the Geological Survey of Western Australia and the Australian National University, led by Arthur J. . The asteroid spewed millions of tons of dust into the sky, blotting out the sun for years and killing most marine invertebrates (animals without backbones), insects, and early reptiles reptiles terrestrial or aquatic vertebrates which breathe air through lungs and have a skin covering of horny scales. They are poikilothermic, oviparous or ovoviviparous, and, if they have legs they are short and constructed solely for crawling. . How did scientists find the buried crater and link it to the mass extinction? Shocked, or fractured, quartz pulled up from a depth of 189 meters (620 feet) at the site, usually signals extreme heat and pressure--"clear cut evidence of a massive impact," says Michael Rampino, an earth scientist at New York University New York University, mainly in New York City; coeducational; chartered 1831, opened 1832 as the Univ. of the City of New York, renamed 1896. It comprises 13 schools and colleges, maintaining 4 main centers (including the Medical Center) in the city, as well as the . Core samples and gravity maps (which show variations in rock density) tipped off geologists to the presence of a "cosmic scar." By examining fossils extracted from the crater base, researchers dated the Woodleigh crater between 200 and 280 million years old. "It must be older than the earth that has filled it, but younger than fossils underneath it," Rampino explains. The mass extinction's timeline falls right in the middle, so an asteroid could be the culprit. But more concrete proof is needed. Stay tuned. |
|
||||||||||||||||||||
Printer friendly
Cite/link
Email
Feedback
Reader Opinion