The Appeal of a Flat Slab (page 2)



Controversy has flourished over the thirty years since the flat slab theory was first proposed. Most of the controversy has been directed at why a subducted plate would become horizontal in the first place and what happened to the plate after the Laramide Orogeny.

But perhaps more critical to the theory is that it seems to fail to explain the complex geometry of the mountain ranges in the South Rocky Mountains, such as the east-west oriented Uinta Mountain Range of northeastern Utah (in red). To explain such unusually oriented mountain ranges, proponents of the flat slab theory have argued for a shift in the orientation of the plate with respect to the North American continent from an east to a more northeast direction (Bird, 1998; Gries,1983; Livaccari, 1991). Another complication to the flat slab theory is the rather flat region of the Colorado Plateau in the southwest, which lies in the hypothesized path of the subducted plate. Although this region shows some rotation during the Laramide Orogeny, it was not uplifted or deformed to a great extent (Cather, 1999).