Oceanic island

An island built on oceanic crust rather than continental crust, commonly by volcanic eruptions or reef growth. Its isolation and oceanic origin shape its geology and ecology.

Hotspot volcanism: Volcanism caused by a relatively persistent mantle source that produces magma as a tectonic plate moves over it. A stationary hotspot can build a chain of oceanic islands as the plate passes overhead.
Oceanic crust: The relatively thin, dense crust underlying ocean basins, formed mainly from basaltic magma. It is the foundation that distinguishes an oceanic island from a continental island.
Hawaiian Islands: A volcanic archipelago in the central Pacific formed as the Pacific Plate moved over a mantle hotspot. The chain records the progression of hotspot-built islands across oceanic crust.
Island biogeography: The study of how species richness on islands relates to area, isolation, immigration, and extinction. Oceanic islands provide clear cases for testing how isolation shapes biodiversity.
Volcanic island: An island formed when volcanic material accumulates above sea level. It is the most common geological form of oceanic island.
Submarine volcano: A volcano whose vent and eruptive activity lie beneath the sea. An oceanic island often begins when a submarine volcano grows above sea level.
Continental crust: The thick, comparatively buoyant crust that underlies continents and some continental islands. Its composition and origin contrast with the oceanic foundation of this island type.
Galápagos Islands: A volcanic archipelago in the eastern Pacific near the Galápagos hotspot and a complex plate boundary. Their active volcanism illustrates oceanic island building near a spreading ridge and hotspot.
Endemism: The restriction of a species or other taxon to a particular geographic area. Long isolation allows oceanic islands to develop species found nowhere else.
Island erosion: The wearing away and transport of island rock and sediment by waves, wind, rain, and gravity. Erosion counteracts volcanic construction and reshapes oceanic island coasts.

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