Abstract
Geologist Walter Alvarez is a scientist best known for his 1980 publication of evidence that a comet or large asteroid collided with the earth 65 million years ago at the end of the Cretaceous period and ultimately caused numerous mass extinctions, including that of the dinosaurs. He has made other significant contributions to science, including to the areas of European plate tectonics and to the age of reversals of the earth’s magnetic field.