Catastrophic events and mass extinctions: impacts and beyond

THE PAST DECADE HAS SEEN MAJOR advances in understanding global catastrophes and mass extinction events. We now accept that the Earth undergoes times when normal background extinction rates are vastly exceeded, but the causes and effects of these events are contentious. The most widely studied and debated extinction horizon is the Cretaceous-Tertiary boundary, which has been one of the central themes of the so-called 'Snowbird' conferences. The fourth was held in Vienna in July 2000 and addressed the question of whether or not, and how, short-term, high-energy events have influenced biological evolution on Earth.