Dynamics of turbidity currents: Gravity-driven erosion and deposition at the

edges of continents

S. Julio Friedmann, Dept. of Geology, Univ. of Maryland, College Park, MD 20742, juliof@geol.umd.edu

Abstract: Turbidity currents are the primary agents of coarse-grained sediment

transport across the continental slope and abyss. These are gravity currents

which flow when sediment suspended in water is more dense than the ambient

fluid (usually sea or lake water). As such, their behavior is very sensitive

to changes in mass and momentum, which are functions of sediment

concentration, grain-size distribution, current height, and gradient. The

critical threshold of erosion is called "ignition", and produces rapid

acceleration and bulking up to a maximum 10% sediment concentration at which

point the primary suspension mechanism, turbulence, is damped. Below the

ignition threshold, turbidity currents will decelerate and dampen to

predicable termination. These strong positive and negative feedbacks can be

indirectly measured in geological and experimental systems and the system

dynamics qualitatively characterized. The relevant parameters can be

collapsed to produce simple phase diagrams that help predict grain-size

distributions, bed characteristics, pore volume connectivity, and behavioral

response. Numerical, experimental, theoretical, and field-based studies will

help to place quantitative constraints on system thresholds and response.