Lincoln F. Pratson¹, Jeffrey Marr², Gary Parker²

(1) Duke University, Durham, NC
(2) University of Minnesota, Minneapolis, MN

ABSTRACT: Experimental Modeling of Submarine Debris Flows

Experiments at St. Anthony Falls Laboratory of the University of Minnesota are revealing how the rheology of submarine debris flows and the existing seafloor topography over which they move affect the shape of debris flow deposits. Deposit shapes are being examined by funneling experimental debris flows through a channel into an open tank, so like real flows, the experimental flows become unconfined.

The experimental flows are given different rheologies and are made to enter the tank at different speeds. The experiments are showing that debris flows with low yield strengths and/or viscosities are broader, rounder and thinner than flows with stiffer rheologies. More interesting is the effect of entrance velocity on flow shape. Flows that enter the open tank at high speeds are broad near the channel mouth and taper toward the head to form an elongated triangle-shaped deposit. In contrast, flows that enter the tank with a no initial velocity, i.e. as a dam break, form deposits that broaden toward their head and are much more eliptical in shape.

Both types of shapes are characteristic of natural debris flow deposits. This suggests that it might be possible to use the shape of a debris flow deposit to constrain the early momentum of the flow following its initiation by a seafloor failure. When coupled with the size of the deposit, it may also be possible to constrain the yield strength and viscosity of the debris flow. These ideas will be investigated further.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado