Fig. 4

Diagram illustrating the importance of distinguishing bottom layer based on fluid rheology and flow state in density-stratified gravity flows, which is based on a photograph of experimental density-stratified gravity flows showing the rheological difference between plastic debris flow (bottom layer) in massive sand and Newtonian turbidity current (top layer). Flow direction to left (arrow length = 10 cm). Note that only Group 1 of researchers would recognize the importance of bottom layer with different rheology and flow state. Note that Postma et al. (1988) would classify both layers together as ‘high-density turbidity current’ (see Fig. 3b). This Mobil-funded experimental flume study was carried out at St. Anthony Falls Laboratory (SAFL), University of Minnesota (1996–1998) under the direction of Professor G. Parker to evaluate the fluid dynamical properties of sandy debris flows. Results were published in two major articles (Shanmugam 2000; Marr et al. 2001;Kuenen 1951)