Invited lecture: Geochemistry of catastrophic events

Catastrophic events in nature are usually associated with slow accumulation of material and/or energy, followed by a rapid surge between different material reservoirs. If the surge exceeds the buffering capacity of the receiving reservoir adverse environmental conditions may result. Volcanism is a prime example, where accumulated matter and energy escapes suddenly from a crustal or mantle reservoir to be added to the surface reservoirs. Subsurface processes may take long time to reach maturity, the final breakthrough, however, is generally short, from a few minutes to a few years. Selected examples of volcanic events that had serious, sometimes catastrophic, concequences will be addressed.