65 million years ago - spectacular end to a spectacular era
Did death come from the skies?
Sixty-five million years ago, a brilliant meteor at least 10 km across ripped through the Earth's atmosphere, striking the ground near Chicxulub on Mexico's Yucatan Peninsula. Rocks and dust exploded 100 km into the air, leaving a crater more than 180 km across and between 28 and 56 km deep.
This image shows a semi-circular crater more than 180 km across. The site of the Chicxulub meteorite impact.
Evidence
A meteorite fragment from Tenham in Queensland is of a similar type to the one that may have caused the mass extinction event 65 million years ago.
Flecks of iron-nickel sparkle in this photograph of the cut surface of a meteorite. Meteorites contain some minerals that are not found in rocks on Earth.
Photo: S Humphreys © Australian Museum.
Iridium is a chemical element that is very rare on Earth but commonly found in meteorites. A thin band of clay, rich in iridium, has been found at more than 100 sites worldwide the fall-out from the dust cloud that circled the Earth after the meterorite impact. Small grains of 'shocked' quartz also occur in this iridium-rich clay layer. 'Shocked' quartz has lines running in many directions, as if it has been fractured for example, by the massive pressure of a meteorite impact.
Photo: Alessandro Montanari, Osservatorio Geologico di Coldigioco.
Massive fires produced by hot projectiles may well have burnt regional forests into a mix of charcoal and dust in which only ferns could survive.
Photo: M Fagg. Copyright © Australian National Botanic Gardens.
