North American Plate

The North American Plate is one of the major tectonic plates. A tectonic plate is a rigid slab composed of the Earth's crust and the upper part of the mantle, which moves gradually across the underlying layer of the lithosphere.

This plate underlies North America, Greenland, and a large portion of the northwestern Atlantic Ocean, including parts of the Caribbean islands and eastern Siberia. It therefore contains both continental and oceanic crust.

Boundaries

On the eastern boundary, the plate meets the Mid-Atlantic Ridge, a divergent boundary where new oceanic crust forms. The North American Plate and the Eurasian and African plates are moving apart at this location. The western boundary is more varied: some sections are transform boundaries, while others are zones where adjacent plates are subducting beneath the North American Plate.

The San Andreas Fault in California is the most well-known example of a transform boundary, where the Pacific and North American plates slide past each other, causing recurring earthquakes. In the north, around Alaska and the Aleutian Islands, the Pacific Plate subducts beneath the North American Plate, producing volcanic activity and major earthquakes.

Movement

The plate moves generally westward to southwestward at a rate of several centimetres per year. This movement is measured using GPS tracking and geodetic surveys. Changes at the plate boundaries affect earthquake hazards in western North America.

Geological history

The North American Plate was part of the earlier supercontinent, particularly Laurasia, before the Atlantic Ocean opened. The opening of the Atlantic has since moved this plate away from the Eurasian Plate, a process that continues to the present day.