A team of government geologists has found new evidence to support the controversial theory that some gigantic object crashed into Earth 65 million years ago and wiped out dinosaurs and many other forms of life.
The scientists, from the U.S. Geological Survey in Denver, said they found quartz grains bearing telltale evidence of shock from a tremendous impact at five sites in Europe, one in New Zealand and one from a drill core sample in the bottom of the Pacific Ocean. Similar quartz grains also have been found in Montana and in the Soviet Union.
All the shocked quartz grains came from deposits that originated at the end of the Cretaceous Period 65 million years ago--about the time when dinosaurs and some other species disappeared.
Nobel laureate Luis Alvarez of the Lawrence Berkeley Laboratory and his son Walter, a University of California, Berkeley, geology professor, proposed seven years ago that the mass extinction was caused by the impact of an asteroid or comet that kicked up a global dust cloud that blocked out sunlight for months. The lack of sunlight would have suppressed photosynthetic processes by which plants grow, thus eliminating food supplies for many creatures.