A Surtseyan eruption is a type of explosive eruption that takes place in shallow seas or

lake A lake is often a naturally occurring, relatively large and fixed body of water on or near the Earth's surface. It is localized in a basin or interconnected basins surrounded by dry land. Lakes lie completely on land and are separate from ...

s when rapidly rising and fragmenting hot

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma (sometimes colloquially but incorrectly referred to as ''lava'') is found beneath the surface of the Earth, and evidence of magmatism has also ...

interacts explosively with water and with water-steam- tephra slurries. The eruption style is named after an eruption off the southern coast of

Iceland Iceland is a Nordic countries, Nordic island country between the Atlantic Ocean, North Atlantic and Arctic Oceans, on the Mid-Atlantic Ridge between North America and Europe. It is culturally and politically linked with Europe and is the regi ...

in 1963 that caused the emergence of a new volcanic island, Surtsey. Surtseyan eruptions are phreatomagmatic (also known as ''hydromagmatic'') eruptions, in that they are violently explosive as a result of vigorous interaction between rising magma and lake or sea water. The magma is commonly basaltic and fragments into small pyroclasts (known as ' ash' and ' lapilli'), and these accumulate around the crater to form a small cone or ring-shaped heap. Volcanoes of this type are known as ' tuff cones' and ' tuff rings' because the volcanic ash of which they are made soon solidifies by chemical reaction into a hard rock known as ' tuff'. Surtseyan eruptions are characteristically unsteady, with phases of rapid repeated short, violent explosions separated by more quiescent phases dominated by steam generation and condensation. Ash and lapilli are emplaced by ash fall (frequently moist or wet), and by short-duration, pyroclastic density currents. The resultant deposits are characteristically well bedded with abundant evidence for moist conditions (e.g. ash aggregates, vesiculated ash layers, and soft-state deformed layers). Much of the wet tephra repeatedly slumps back down into the volcano's crater to be re-ejected by further watery explosions.

Characteristics

Although similar in nature to phreatomagmatic eruptions, there are several specific characteristics: *Physical nature of magma:

basalt Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...

ic. *Character of explosive activity: violent ejection of solid, warm fragments of new magma; continuous or rhythmic explosions; base surges. *Nature of effusive activity: short, locally pillowed,

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

flows (which may be rare). *Nature of dominant ejecta: lithic, blocks and ash; often accretionary lapilli; spatter, fusiform bombs and lapilli absent. *Structures built around vent: tuff rings

Examples of Surtseyan eruptions

* Bogoslof Island -

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, United States, 1796 * Fire Island -

, United States, 1796 * Graham Island -

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, 1831 * Anak Krakatau - Sunda Strait,

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, 1927–1930 (with smaller eruptions continuing today) - further Surtseyan eruptions took place following the December 2018 eruption which left large sections of the volcano underwater * Shōwa Iōjima - Iōjima, Kagoshima, Japan, 1934 * Capelinhos -

Faial Island Faial Island (), also known as Fayal Island, is a Portugal, Portuguese island of the Central Group or ''Grupo Central'' of the Azores, in the Atlantic Ocean. The Capelinhos volcano is the westernmost point of the island and is considered the we ...

Azores The Azores ( , , ; , ), officially the Autonomous Region of the Azores (), is one of the two autonomous regions of Portugal (along with Madeira). It is an archipelago composed of nine volcanic islands in the Macaronesia region of the North Atl ...

, 1957–1958 * Surtsey -

, 1963 * Jólnir -

, 1966 * Taal Volcano - Batangas,

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(last erupted in 2021) * Zubair Group -

Yemen Yemen, officially the Republic of Yemen, is a country in West Asia. Located in South Arabia, southern Arabia, it borders Saudi Arabia to Saudi Arabia–Yemen border, the north, Oman to Oman–Yemen border, the northeast, the south-eastern part ...

, 2011–2012 * El Hierro -

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, 2011–2012 (see 2011–12 El Hierro eruption) * Fukutoku-Okanoba,

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, Japan, 2021 * Hunga Tonga-Hunga Ha'apai,

Tonga Tonga, officially the Kingdom of Tonga, is an island country in Polynesia, part of Oceania. The country has 171 islands, of which 45 are inhabited. Its total surface area is about , scattered over in the southern Pacific Ocean. accordin ...

, 2021—2022 (see 2022 Hunga Tonga–Hunga Ha'apai eruption and tsunami)

References

*Kokelaar, B.P (1983) The Mechanisms of Surtseyan volcanism. Journal of the Geological Society, London.140, 939–944. {{Types of volcanic eruptions