Summary: Catastrophism is the idea that natural disasters have had a significant influence in moulding the Earth's geological features. In 1822 William Buckland ascribed most of the fossil record to the effects of Noah's flood. Charles Lyell later challenged these writings, arguing that geological change was slow and gradual, and that the processes responsible could still be seen at work today - a theory known as Uniformitarianism. But in the 1970s the idea that catastrophes were a major factor in the Earth's geology was revived by the discovery of evidence of a giant asteroid impact 65 million years ago, believed by many to have caused the extinction of the dinosaurs. Melvyn Bragg is joined by Andrew Scott, Leverhulme Emeritus Fellow in the Department of Earth Sciences at Royal Holloway, University of London; Jan Zalasiewicz, Senior Lecturer in Geology at the University of Leicester and Leucha Veneer, Visiting Scholar at the Faculty of Life Sciences at the University of Manchester.
