Gold miners in the Australian Outback recently discovered a gigantic meteorite crater dating to about 100 million years ago, back when dinosaurs roamed the Earth.
Found near Ora Banda, the newly dubbed Ora Banda Impact Crater is about 5 km across. This huge hole was likely created by a meteorite up to 660 feet wide, or longer than the length of two American football fields.
When geologists at Evolution Mining, an Australian gold mining company, came across some unusual rock cores at Ora Banda, they called Jayson Meyers, geophysicist, who immediately noticed the shatter cones — telltale signs of a meteorite crash.
Shatter cones form when high-pressure, high-velocity shock waves from a large impacting object — such as a meteorite or a gigantic explosion (such as would occur at a nuclear testing site) — rattle an area. These shock waves shatter rock into the unique shatter cone shape, just like a mark that a hard object can leave on a car’s windshield.
Meyer’s work revealed a hidden impact crater with a pucker in the middle. This pucker is where shattered rocks came back to the surface after the meteorite struck, like a compressed spring that bounces back. When the geologists went to the “pucker” part of the site, they discovered shatter cones in the rocky outcrops.
Now, scientists are investigating the Ora Banda site on a microscopic level. In particular, the team will examine whether minerals at the site were vapourized and then re-crystallized under high pressures.
Research on zircons and other minerals from the crater will likely reveal when the meteorite struck — right now, scientists think it hit between 250 million and 40 million years ago.