Mass Extinctions of Species — Were Dinosaurs Killed by An Asteroid or Volcanoes?

Abstract

Mass extinctions of a large fraction of the world’s species occur periodically. About 65 million years ago, some 20% of all species vanished and the sudden change in the fossil record [e.g. dinosaurs are found before but not afterwards] defines the Creteous/Tertiary, K/T, geological boundary. Luis Alvarez et al.1 suggested that because of the high iridium occurrence at the K/T boundary, that an asteroid impact had caused this mass extinction. However the asteroid which hit Yucatan 65 million years ago is shown to be rather too small for all the damage caused and there is a poor correlation between asteroid impacts and mass extinctions. Data is presented on the effects of volcanoes and it is shown that there is an excellent correlation between major volcanic eruptions and mass extinctions. In particular the great volcano eruptions in India that created the Deccan flats some 65 million years ago are responsible for most of the K/T mass extinctions. It is proposed that the impact of an asteroid causes concentrated shock waves at the antipodes of the impact, so that any volcanic eruptions there are reinforced. Hence the asteroid which hit Yucatan increased the volcanic eruptions in India and enhanced the strength of the K/T mass extinctions. Most of the extinctions of species occurred before the Yucatan impact in the early stages of the volcanic eruptions but the asteroid impact would have increased the strength of the species extinctions.