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).

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

On average, the Pacific Plate moves at 50 - 100 mm (5 - 10 cm) per year. However, the Pacific, Cocos, Nazca, and Antarctic plates move more than 100 mm (10 cm) yearly, 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 revolves around a point south of Australia. Around Hawaii, the plate is moving at about 7 cm/year.

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

Pacific Plate Boundaries

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

• Divergent boundaries: places where two tectonic plates are moving away from each other. This creates a gap between the plates, where the magma from the Earth's mantle can rise to the surface and create a new oceanic crust.

• Convergent boundaries: places where two tectonic plates are moving toward each other. This can result in one plate being subducted beneath the other or in the two plates colliding head-on. For example, if one plate is oceanic and the other is continental, the oceanic plate will typically be subducted beneath the continental plate. This process is known as subduction.

• Transform boundaries: places where two tectonic plates move past each other in opposite directions. Earthquakes typically characterize these boundaries as the plates grind against each other.

The Pacific Plate's boundaries are complex and vary depending on the location. Generally, the plate is bounded by divergent boundaries in the east, convergent boundaries in the west, and transform boundaries in the north and south.

• The eastern boundary of the Pacific Plate is a divergent boundary where the plate is spreading apart from the Cocos Plate and Nazca Plate. The East Pacific Rise, a mid-ocean ridge along the equator, marks this boundary.

• The western boundary of the Pacific Plate is a convergent boundary where the plate is subducting under the Eurasian, Philippine, and North American plates. Subduction zones, including the Aleutian, Mariana, and Philippine trenches, mark this boundary.

• The northern boundary of the Pacific Plate is a transform boundary where the plate is sliding past the North American Plate. This boundary is marked by the San Andreas Fault, which runs along the west coast of the United States.

• The southern boundary of the Pacific Plate is a transform boundary where the plate is sliding past the Australian Plate. This boundary is marked by the Macquarie Ridge, a mid-ocean ridge that runs south of New Zealand.

Pacific Plate Boundaries in the Americas

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

A convergent boundary subducts under the North American Plate on the Pacific Plate's northern side, 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, a divergent boundary with the Nazca Plate forms the East Pacific Rise.

On the southern side, a divergent boundary with the Antarctic Plate forms the Pacific-Antarctic Ridge.

Baja California Peninsula

The Pacific and North American Plates movement 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).

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}