Did volcanic eruptions cause the dinosaurs to become extinct?
Not quite, but it decreased their diversity enough that the asteriod impact 65 million years ago was the fatal blow to most of the large forms. The smaller forms survived and today are known as birds. The proof is generally believed to be a thin layer of Iridium enriched sediment laid down on nearluy every continent which dates to 65 million years ago. Iridium is very rate on earth, but common in meteors. By the end of the cretaceous period many kinds of dinosaurs had already become extinct. The most notable were the giant sauropods. The meat eating theropods demonstrated their decline in species diversity at the time by being either tiny like raptors were (under 3 feet) or the single, giant form, T. Rex at over 18 feet tall. The decline in dinosaur species during the cretaceous period was attributed to an increase in volcanic activity. Volcanic activity is evident in the fossil layer by the deposition of volcanic dust. This results in layers of light colored sediment high in silicates
