Farallon plate

Since the North American west coast has a convoluted structure, significant work has been required to resolve the complexity.

[3][5][6][7] This phenomenon is one that accounts for the far-inland orogenisis 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.

There is a concentration of velocity anomalies in the tomography that is thicker than the slab itself should be, indicating that folding and deformation occurred beneath the surface during subduction.

[2][10] 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.

[11] 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.

Map of the Panthalassic ocean c. 180 million years ago, showing the position of the Farallon plate
Formation of the Juan de Fuca (including Explorer and Gorda) and Cocos plates (including Rivera) and of the San Andreas Fault from the Farallon plate
Tomographic imaging of the subducted Farallon plate beneath North America, showing that the velocities of sesimic waves vary based on the temperature of the material they are moving through.
A software model by NASA of the remnants of the Farallon plate, deep in Earth's mantle
Map showing some of the accreted terranes in present-day California.
Region of the modern Cascadia subduction zone, where the Juan de Fuca plate (a remnant of the Farallon plate) is subducting