A review of open-channel megaflood depositional landforms on earth and mars

Summary. Catastrophic out-bursts of water from lakes impounded by glacial ice or debris such as moraines have caused large freshwater floods on Earth in recent times at least back to the Quaternary. Resultant large-scale depositional sedimentary landforms are found along the courses of these floodwaters. On Mars, similar floods have resulted from catastrophic efflux of water from within the Martian crust. This latter conclusion is based on large-scale and mesoscale landforms that appear similar to those identified in flood tracts on Earth. Both on Earth and on Mars, these landforms include suites of giant bars – ‘streamlined forms’ – of varying morphology that occur primarily as longitudinal features within the floodways as well as in flooded areas that were sheltered from the main flow. Flow-transverse bedforms, notably giant fluvial dunes and antidunes also lie within the floodways. The flood hydraulics that created these forms may be deduced from their location and morphology. Some other fluvial landforms that have been associated with megafloods on Earth have yet to be identified on Mars. Introduction. Exceptionally large freshwater floods on Earth are associated with the catastrophic draining of glacial lakes Missoula and Agassiz amongst others in North America (Teller, 2004). Other glacially related large floods occurred in the mountains of Eurasia, which have only recently received attention (Grosswald, 1999; Montgomery et al., 2004), and geomorphological evidence of other large floods may be discovered in formerly glaciated terrain on other continents.