Pacific Plate

Extent and boundaries

The plate covers an area on the order of 100 million square kilometers and is bordered by a mixture of divergent, convergent and transform faults. To the west and northwest it meets plates that subduct beneath continental Asia and island arcs; along much of its eastern margin it is bounded by spreading centers and transform faults. For visual reference, consult a map of ocean-floor tectonics such as a Pacific Ocean floor map.

Geology and age of the seafloor

Most of the Pacific Plate is made of relatively young oceanic crust created at mid-ocean ridges. Seafloor magnetic patterns and radiometric dating show that preserved oceanic crust rarely exceeds the early Cretaceous in age (about 145 million years), because older lithosphere is typically consumed at subduction zones. In other words, the plate both produces new crust at spreading centers and destroys older crust where it plunges into the mantle.

Volcanism and hotspots

The plate hosts long-lived volcanic activity, including chains formed by mantle hotspots. The Hawaiian Islands are a classic example of a hotspot track on the Pacific Plate; the time-progressive chain records the plate's motion over a relatively fixed mantle heat source. For discussion of this feature see the Hawaiian hotspot.

Ring of Fire and subduction

The Pacific Plate's margins coincide with much of the circum-Pacific "Ring of Fire," an area of frequent earthquakes and volcanic eruptions. Convergent boundaries along the plate produce deep ocean trenches and volcanic arcs (for example the Aleutians, Japan, and the Andes where other plates interact), and transform faults accommodate lateral motion between plates.

Importance and study

Studying the Pacific Plate provides insight into plate motion, mantle processes, and natural hazards. Ocean drilling, seismic imaging, and satellite geodesy have clarified its kinematics and internal structure. Understanding this plate helps explain regional geology, earthquake risk, island formation and the global cycle of crustal creation and destruction.

• Key features: largest plate, oceanic crust, hotspot tracks.
• Processes: seafloor spreading, subduction, transform faulting.
• Significance: shapes Pacific geology, controls many seismic and volcanic hazards.