sábado, 21 de julho de 2018

Manicouagan Crater: One Of The Oldest Known Impact Craters.

 Lake Manicouagan in northern Quebec, Canada, as seen by NASA's Terra satellite on June 2001
Manicouagan Crater is located in Canadian province of Québec, and is one of the Earth’s oldest and the most visible impact craters. Manicouagan Crater was formed by a 5-km (3.1 mi) bolide (asteroid or a yet larger comet) strike this area, then part of Pangaea, over 214 million years ago during the Triassic Period of the Mesozoic Era. The impact may have played a role in the fourth major mass extinction of species that occurred about the same time.

This mass extinction event was actually a combination of smaller mass extinction periods that happened over the final 18 million years or so of the Triassic Period. Over the course of this extinction event, it is estimated more than half of the known living species at the time completely died out. This allowed dinosaurs to thrive and take over some of the niches left open due to the extinction of species that had previously held those types of roles in the ecosystem.

The impact caused a fireball as far as present-day New York, a melting pot boiling the local bedrock over 50 km extent and 9 km depth, and a crater wall of about 70 km (40 mi) diameter inner ring. Like a pebble creating ripples when dropped into water, the crater has concentric rings formed by shock waves transmitted by the impact. The total diameter of the concentric rings is 100 km (60 mi) across. The rim-to-diameter measurement makes it the sixth-largest confirmed impact crater.
The crater contains an annular lake called Manicouagan Reservoir which surrounds René-Levasseur Island. Together, the lake and the roughly 2,000 sq km (772.2 sq mi) island are known as the “eye of Québec.” It is one of the most striking structures on the face of the Earth and the most obvious impact scar. It may have been part of a multiple impact event which also formed the Rochechouart crater in France, Saint Martin crater in Manitoba, Obolon' crater in Ukraine, and Red Wing crater in North Dakota.

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