Global Megaflood Paleohydrology

After centuries of geological controversy, it is now well-established that the last major deglaciation of planet Earth involved huge fluxes of water from the wasting continental ice sheets, and that much of this water was delivered as floods of immense magnitude and relatively short duration. These late Quaternary megafloods had short-term peak flows comparable in discharge to the more prolonged fluxes of ocean currents. The discharges for both ocean currents and megafloods generally exceed a flow of one Sverdrup (Sv), or one million cubic meters per second, hence the prefix “mega.” A global inventory of these phenomena includes more than 40 examples from Asia, Europe, North America, South America, and Iceland. Though there have been many advances in understanding the physical processes and geochronology of megaflooding, important controversies remain, including the nature of subglacial megaflooding, the details of the immense network of megaflood landscape features in Asia, and the causes of huge megaflood channels on the planet Mars. However, it is becoming increasing clear that immense outburst floods likely induced very rapid, short-term effects on the planetary environments on both Earth and Mars, greatly altering climates, drainage evolution, and the planetary patterns of water and sediment movement to lakes, seas, and oceans.