Different types of mass movement can be classified based on the moisture content of the moving material and the speed of movement: mudflow requires high moisture content combined with relatively rapid movement (a wet, fluid-like mass moving quickly downslope); rotational slump involves a coherent block of material moving along a curved failure surface at a moderate, intermediate rate; soil creep is an extremely slow, near-imperceptible downslope movement that can occur even under relatively low moisture conditions, driven by repeated small-scale expansion/contraction; and rockfall is a very rapid, largely dry (moisture-independent) movement of rock material under gravity with essentially no fluid/plastic behavior.