Global & Disaster Medicine

Plate Tectonics & The Ring of Fire

National Park Service

The Earth is made up of roughly a dozen major plates and several minor plates. These plates are constantly moving, some as fast as 15 centimeters a year



SUBDUCTION ZONE:  At a convergent plate boundary the older, more dense crust will sink, or “subduct” under the other. There can be a Normal-Angle Subduction and a Low-Angle Subduction.


ISLAND ARC SETTING:  An island-arc setting includes a chain of offshore, island volcanoes above a subducting plate. The back-arc is located opposite the trench and subducting plate, behind the chain of volcanoes called an “island arc”.


HOTSPOTS:  This graphic shows the evolution of a chain of islands over stationary mantle plume (hotspot) within Earth’s crust.


PACIFIC OCEAN HOTSPOTS:  Tectonic setting of the Pacific Plate with selected hotspots indicated. The “kink” between the Emperor Seamounts and Hawaiian Islands chain shows how the direction of plate motion changed while the Hawaiian hotspot remained stationary.

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