On the continental shelf and slope off the Pacific Northwest of coast USA is an intricate system of canyons and channels carved by outwash flows over many 1000s of years. The upper reaches of these canyons slowly accumulate sediment. Big earthquakes shake this material loose and it runs down the slope as a turbidity current. Deposits left behind are dated and fix a 12,000 year long history of Cascadia earthquakes. This movie shows physics based simulations of turbidity currents.