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Born in Berkeley, California, he earned his B.A. in geology in 1962 from Carleton College and Ph.D. in geology from Princeton University in 1967.
Alvarez and his father were known for their theory that the boundary between the Cretaceous and Tertiary (K-T) layers of sediment are abnormally high in iridium. As iridium may be found in some types of asteroids, they posited that it was an asteroid impact that was responsible for this layer, which appears to be contemporaneous with the K-T extinction, 65 million years ago, at which time some 85% of all species disappeared, including all of the dinosaurs.