Volcanic tsunami

[1] Volcanic tsunamis produced by large lateral collapse landslides and ocean-entering pyroclastic flows are the largest and most hazardous.

An underwater explosion resulting in the formation of a crater can cause subsequent expansion, rise and gravitational collapse to create tidal bores, as well as smaller waves.

[3] Most waves caused by underwater volcanic explosions have small amplitudes, an exception being those produced by the 1996 eruption of Karymsky Lake in Russia which reached heights of up to 10 m (33 ft) or more.

[3] Underwater caldera collapse resulting from large explosive eruptions can cause tsunamis due to subsidence of the water surface.

Such earthquakes can reach magnitudes greater than 6 and may occur on large thrust faults at the base of volcanic edifices.

For example, a Ms 7.2 earthquake in Hawaii associated with large-scale slumping of Kīlauea's southern submarine flank caused the 1975 Kalapana tsunami.

[4] The slopes of many volcanoes are naturally unstable due to magmatic intrusions, structural discontinuities, high lava accumulation rates and hydrothermal alteration.

Slope failures of volcanic edifices produce a wide spectrum of instability phenomena ranging from rockfalls and small landslides to large debris avalanches.

Limnic eruptions are a very rare phenomenon involving sudden discharges of volcanic gases from deep lake waters.