Impact Melt at Memory Bay

April 05, 2008

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Provided by: Charles O'Dale
Summary author: Charles O'Dale 

This photo shows a meteor impact melt cliff found in the central peak area of the Manicouagan Impact Structure, Quebec, Canada. Approximately 214 million years ago, an estimated 10 k (6.2 mi) wide bolide impacted here at a velocity of between 12 and 30 k (7.4 and 18.6 mi) per second. The resultant 100 k (62 mi) diameter crater is one of the largest impact craters still preserved on the surface of the Earth. The water filled circular annular moat that's prominent on images taken from Earth orbit is only one third of the size of the original crater. This moat fills a ring where impact-brecciated rock was eroded away by glaciation.

The illustrated impact melt cliff and talus (debris at the base of the cliff) is composed of target rock that was made temporarily molten from the energy released during the impact of the bolide. The heat released was so intense that's believed it took 1,600 to 5,000 years before the melted rocks cooled. There's no detectable meteorite component in the Manicouagan structure melt rock (Palme et al., 1978). This impact melt and talus outcrop is found in an inlet, cut into the central peak of the impact structure, known as Memory Bay. Since the impact, millions of years of erosion have created the existing landforms at the Manicouagan impact structure.