guyot

A guyot is a flat-topped submarine volcano or seamount. Unlike conical seamounts with pointed summits, a guyot has a wide, level summit that lies below the ocean surface. They are built by volcanic activity on the seafloor and are typically remnants of former islands that were planed smooth by wave action when near sea level, then subsided below the surface as the oceanic crust cooled and sank.

Formation and morphology: The process begins with submarine volcanic activity on a hotspot or along a mid-ocean ridge. As the volcano grows and approaches sea level, wave erosion flattens the summit. Subsequent subsidence of the lithosphere lowers the feature below the surface, leaving the flat top at a depth where it is no longer actively eroded by waves. The sides are steep, and the base extends into the deep ocean. The flat summit is often covered by sediment or colonized by deep-sea organisms, and the structure may be truncated by further tectonic or sedimentary processes.

Distribution and significance: Guyots are widespread in all oceans and are commonly identified using bathymetric surveys and seismic data. They provide records of past sea levels and plate tectonics, helping scientists understand ocean floor evolution and the history of island subsidence.

Etymology: The term guyot honors Arnold Henry Guyot, a 19th-century geologist and geographer whose work contributed to the study of marine topography.