As an ancient tectonic plate, the Farallon plate must be studied using methods that allow researchers to see deep beneath the Earth's surface. The understanding of the Farallon plate has evolved as details from
seismic tomography provide improved details of the submerged remnants. Since the North American west coast has a convoluted structure, significant work has been required to resolve the complexity. Seismic tomography can be used to
image the remainder of the subducted plate because it is still "cold," meaning that it has not reached
thermal equilibrium with the mantle. This is important for the use of tomography because
seismic waves have different velocities in materials of different temperatures, so the Farallon slab appears as a velocity anomaly on the tomography model.
Shallow angle subduction and deformation Multiple studies show that the subduction of the Farallon plate was characterized by a period of "
flat-slab subduction," which is the subduction of a plate at a relatively shallow angle to the overriding crust (in this case, North America). This phenomenon accounts for the far-inland
orogenesis of the
Rocky Mountains and other ranges in North America which are much farther from the
convergent plate boundary than is typical of a subduction-generated
orogeny. In addition to influencing slab buoyancy, some oceanic plateaus may have also become accreted to North America.
Interpretations of Farallon plate subduction A 2013 study proposed two additional now-subducted plates that would account for some of the unexplained complexities of the accreted terranes, suggesting that the Farallon should be partitioned into Northern Farallon,
Angayucham,
Mezcalera and Southern Farallon segments based on recent tomographic models. Under this model, the North American continent overrode a series of subduction trenches, and several
microcontinents (similar to those in the modern-day
Indonesian Archipelago) were added to it. These microcontinents must have had adjacent oceanic plates that are not represented in previous models of Farallon subduction, so this interpretation brings forth a different perspective on the history of collision. Based on this model, the plate moved west, causing the following geologic events to occur: Other models have been proposed for the Farallon's influence on the Laramide orogeny, including the
dewatering of the slab which led to intense uplift and
magmatism. == See also ==