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.