Pacific Tectonic Plate

The Pacific Plate is an oceanic tectonic plate, made up almost entirely of oceanic crust, that lies beneath the Pacific Ocean. It is Earth's largest tectonic plate at an estimated 103,280,000 sq km (40,000,000 sq mi).

On its eastern side, the Pacific Plate stretches all the way along the west coast of North America up to Alaska.

The Pacific Plate forms a large portion of the Pacific Ring of Fire. This horse-shoe-looking pattern of plate tectonics has some of the most catastrophic earthquakes and volcanoes on Earth.

On average, the Pacific Plate moves at a rate of 50 - 100 mm (5 - 10 cm) per year. However, the Pacific Plate, Cocos Plate, Nazca Plate, and Antarctic Plate move more than 10 centimeters, the fastest movement rate of all plate tectonics.

Plate Tectonics

The theory of plate tectonics states that the Earth's solid outer crust is separated into plates that move over the molten upper portion of the mantle. Convergence occurs when two plates are pushing into each other. Divergence occurs when plates pull away from each other.

The floor of the Pacific Ocean is divided into several plates. The Pacific Plate is the largest, moving northwest relative to the North American Plate.

Nothing moves along a straight line on the Earth's surface. Instead, the plates rotate around a point on the surface. For example, the Pacific Plate rotates around a point south of Australia. Around Hawaii, the plate is moving at about 7 cm/year.

_{Map of the Pacific Plate boundaries and relative motion}

Pacific Plate Boundaries in the Americas

Where two plates meet, there can be three types of boundaries:

• transform faults: where the plates slide past each other

• spreading centers: where two plates are moving away from each other

• subduction zones: where one plate dives into the Earth under another plate

On the northern side of the Pacific Plate, there is a convergent boundary subducting under the North American Plate, forming the Aleutian Trench.

In the middle of the eastern side is a transform boundary with the North American Plate and a boundary with the Cocos Plate.

On the southeastern side, there is a divergent boundary with the Nazca Plate, forming the East Pacific Rise.

On the southern side, there is a divergent boundary with the Antarctic Plate, forming the Pacific-Antarctic Ridge.

Baja California Peninsula

Movement of the Pacific and North American Plates began pulling the Baja California Peninsula and the western half of Southern California away from mainland Mexico about six million years ago, opening up the Gulf of California (Sea of Cortez) in the process.

Since then, the tectonic plate has moved some 330 km (200 mi) northwards, carrying Baja California and peninsular Southern California along with it.

_{Map illustrating the major tectonic plates of the world}