Posted: Mon Jan 16, 2006 9:12 pm
I was looking at Google maps some time ago and saw this curious feature to the right of the "c" in Quebec, so I had to look it up (check this link to see what it looks like on Google map): http://maps.google.com/?ll=52.268157,-7 ... ,58.095703Jbuza wrote:Meteoroids of more than about 10 tons (9,000 kg) will retain a portion of their original speed, or cosmic velocity, all the way to the surface.
[Quote from link below:]
The target rock in the vicinity of the crater is Grenville age amphibolite to granulite facies quartz and feldspar gneiss, with local anorthosites, metagabbro and metasediments overlain by Ordovician limestones, dolomites, slates and sandstones. The force of the impact exhumed and liquefied these target rocks down to as deep as 9 kilometres. The crater became a melting pot for relatively young rocks at the surface and for much of the older minerals originally buried kilometres below the site of the impact. The heat released was so intense that it took between 1,600 and 5,000 years before the melted rocks cooled.
The Manicouagan impact was so forceful that it ejected material out of the atmosphere and sent it on a ballistic trajectory around the earth. Like the Chicxulub impact, the Manicouagan impact left behind a global geochemical signature in the rock record (Note 3). The impact also triggered powerful seismic events (Note 4). The fireball generated by the impact probably expanded as far as the present location of New York City. Click for full viewFive geological features of the crater were defined by Grieve and Head in 1983 and are labeled in the LANDSAT image (Courtesy NASA/LPI) as follows:
* outer disturbed zone 150 km in diameter;
* inner fracture zone 100 km in diameter;
* annular moat 65 km in diameter;
* inner plateau 56 km in diameter, and;
* central uplift region 25 km in diameter.
http://ottawa.rasc.ca/astronomy/earth_c ... nicouagan/