June 29th, 2012 by Joshua S Hill
A massive 100 kilometre-wide crater has been discovered in Greenland and redefined the record books by being the remains of an impact that is a full billion years earlier than any other known collision on Earth.
It’s a fascinating story and one that will continue to evolve and should help shed light on a period of time we don’t know so much about. The craters that speckle the Moon were crated by impacts with asteroids and comets between 3 and 4 billion years ago, but with its much larger gravitational field the Earth surely would have suffered even more. However, time and erosion have destroyed most signs of these impacts. Previous to this latest discovery, the oldest known crater on Earth was created 2 billion years ago.
The research was conducted by a team of scientists from Cardiff, the Geological Survey of Denmark and Greenland (GEUS) in Copenhagen, Lund University in Sweden and the Institute of Planetary Science in Moscow and funded by GEUS and the Danish ‘Carlsbergfondet’ (Carlsberg Foundation).
The team of scientists discovered the remains of a massive 3 billion year old impact that is located near the Maniitsoq region of West Greenland.
“This single discovery means that we can study the effects of cratering on the Earth nearly a billion years further back in time than was possible before,” according to Dr Iain McDonald of the School of Earth and Ocean Sciences, who was part of the team.
But the discovery was not as simple as happening across a soft patch of snow and digging. The evidence was not as obvious as a bowl-shaped crater. Since the impact, the land has been eroded down to expose deeper crust 25 kilometres below the original surface. The bowl came and went long ago. All external parts of the impact structure have been removed by natural forces and time.
However, the effects of such a massive impact on the Earth remain thanks to the impact shock wave that would have penetrated deep into the crust, far deeper than any previously known crater. It was these that the scientists discovered and studied.
But because such an impact has never been studied before, the effects of impact at the depths involved have forced the scientists into three years of painstaking research to assemble all the key evidence to convince the scientific community.
“The process was rather like a Sherlock Holmes story,” said Dr McDonald. “We eliminated the impossible in terms of any conventional terrestrial processes, and were left with a giant impact as the only explanation for all of the facts.”
Dr McDonald added: “It has taken us nearly three years to convince our peers in the scientific community of this but the mining industry was far more receptive. A Canadian exploration company has been using the impact model to explore for deposits of nickel and platinum metals at Maniitsoq since the autumn of 2011.”
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