प्लेट टेक्टोनिक्स

The tectonic plates of the world were mapped in the second half of the 20th century.

Remnants of the Farallon Plate, deep in Earth's mantle. It is thought that much of the plate initially went under North America (particularly the western United States and southwest Canada) at a very shallow angle, creating much of the mountainous terrain in the area (particularly the southern Rocky Mountains).