Extreme Events in the Geological Past

Abstract

Many Xevents in the geological past exceeded the strengths and intensities observed for modern-day natural events. The number of extraordinary events that occurred in the geological past is of course much larger than the number we witness today because the geological timescale covers millions of years. This contribution focuses on these Xevents from earth’s geological history, including selected examples from plate tectonics, earth magnetism, ice age cycles, volcanism, earthquakes, meteorite impacts and floods. Events related to these processes occur on different timescales. For example, drastic modifications of atmospheric and oceanic circulation due to continental shift (which creates new mountain ranges and reshapes land masses and oceans) take millions of years, while meteorite impacts happen within seconds. However, any these processes can be the trigger for dramatic consequences, like mass extinctions of life, or global glaciations. An overview of a research program that considers historic and prehistoric flood events is given. Based on the water levels observed during floods, the palaeodischarge can be determined and used to improve the reliability of flood predictions. Investigations of Pleistocene ice-dammed lake outburst floods (the largest flood events in the Earth’s history) are useful when developing new methods and techniques that can be applied to younger events of a smaller scale in other environments.