The large annular lake in this image represents the remnants of one
of the largest impact craters still preserved on the surface of the
Earth. Lake Manicouagan in northern Quebec, Canada, surrounds the
central uplift of the impact structure, which is about 70 kilometers in
diameter and is composed of impact-brecciated (relatively large pieces of rock embedded
in finer grained material) rock. Glaciation and other
erosional processes have reduced the extent of the crater, with the
original diameter estimated at about 100 kilometers (60 miles). This natural-color
image of the region was acquired by the Multi-angle Imaging Spectroradiometers
(MISRs) nadir (vertical-viewing) camera on June 1, 2001.
The impact that formed Manicouagan is thought to have occurred about
212 million years ago, toward the end of the Triassic period. Some
scientists believe that this impact may have been responsible for a mass
extinction associated with the loss of roughly 60 percent of all species. It
has been proposed that the impact was created by an asteroid with a
diameter of about 5 kilometers. The lake is bounded by erosion-resistant
metamorphic and igneous rocks, and shock metamorphic effects are
abundant in the target rocks of the crater floor. Today Lake Manicouagan
serves as a reservoir and is one of Quebecs most important regions for
Atlantic salmon fishing.
NASA image courtesy NASA/GSFC/LaRC/JPL, MISR Team.
Lake Jänisjärvi is a roughly oval-shaped lake, some 13 by 17 kilometers (8 by 11 miles) across, in northwestern Russia, near the Finnish border. The basin for this lake was formed hundreds of millions of years ago by a meteorite impact.