Overview

A guyot, also called a tablemount, is an underwater volcanic mountain distinguished by a relatively flat summit. These features are generally found well below sea level—typically more than 200 meters beneath the surface—and some flat summits extend for many kilometers in diameter. Guyots are a familiar component of the ocean floor and are often grouped with other seamounts in linear chains or fields.

Formation and characteristics

Guyots begin as volcanic islands or submarine volcanoes. While active or shortly after activity ends, wave action and coastal processes can erode the volcanic top when it stands near or above sea level, producing a planar surface. Over geological time the volcanic edifice cools and the lithosphere on which it rests subsides, carrying the flattened top below the sea. In many cases the flat cap contains shallow‑water limestones or reef deposits that were formed before drowning.

Key characteristics include:

  • Flat, often broad summit produced by erosion or biogenic construction.
  • Volcanic origin with basaltic foundations overlain by sedimentary or carbonate deposits.
  • Common occurrence in chains associated with hotspots or spreading centers.
  • Summit depths typically exceeding 200 m and diameters that can exceed 10 km.

Distribution, examples and research

Guyots are widespread on the abyssal plains and continental margins. Many were mapped during the 20th century using echo‑sounding and later sampled by ocean drilling programs, which recovered shallow‑water limestones and reef material atop volcanic bases—evidence for former emergence and later subsidence. Famous groups of seamounts and guyots appear along hotspot tracks and in the Pacific, for example along the Emperor–Hawaiian chain.

Ecological and scientific importance

Although submerged, guyots influence ocean currents and provide hard substrate for marine life, hosting communities of corals, sponges and fish distinct from surrounding plains. Their caps may host ferromanganese crusts and other mineral deposits that attract interest for resource exploration, while the underlying structure and deposits preserve records of past sea levels, climate and volcanic activity important to paleoceanography and plate tectonic studies.

For general context on related submarine mountains see seamount. The term "guyot" commemorates the 19th‑century geographer Arnold Henry Guyot and remains in use among oceanographers and geologists to describe these flat‑topped undersea features.