Submarine eruptions are those

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates ...

eruptions which take place beneath the surface of water. These occur at constructive margins,

subduction Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, ...

zones and within

tectonic plates Plate tectonics (from the la, label=Late Latin, tectonicus, from the grc, τεκτονικός, lit=pertaining to building) is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large ...

due to hotspots. This eruption style is far more prevalent than subaerial activity. For example, it is believed that 70 to 80% of the Earth's magma output takes place at mid-ocean ridges.Parfitt, L. and Wilson, L. (2008) ''Fundamentals of Physical Volcanology'', Blackwell Publishing.

Detection

Fukutoku-Okanoba Eruption 08-12-2022 2127Z to 08-13-2022 0335Z

Submarine eruptions are less studied than subaerial

volcanoes A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates a ...

due to their inaccessibility. Developments in technology mean that

submarine volcanoes Submarine volcanoes are underwater vents or fissures in the Earth's surface from which magma can erupt. Many submarine volcanoes are located near areas of tectonic plate formation, known as mid-ocean ridges. The volcanoes at mid-ocean ri ...

can now be studied in greater detail. Despite this progress, understanding is still limited. Mid ocean ridges for example are the most active volcanic systems on Earth but roughly only 5% of their length has been studied in detail.Fagents, S.A., Gregg, T.K.P. and Lopes, R.M.C. (2013) ''Modelling Volcanic processes: the Physics and Mathematics of Volcanism'', Cambridge University Press, UK. Initial knowledge of these eruptions came from

volcanic rocks Volcanic rock (often shortened to volcanics in scientific contexts) is a rock formed from lava erupted from a volcano. In other words, it differs from other igneous rock by being of volcanic origin. Like all rock types, the concept of volcan ...

being recovered from the ocean floor when repairs were made to the

Transatlantic telegraph cable Transatlantic telegraph cables were undersea cables running under the Atlantic Ocean for telegraph communications. Telegraphy is now an obsolete form of communication, and the cables have long since been decommissioned, but telephone and data a ...

in the 1800s.Rubin, K.H., Soule, S.A., Chadwick, W.W., Farnan. D.J., Clague, A.A., Emberley. R.W., Baker, E.T., Perfit, M.R., Caress, D.W. and Dziak, R.P. (2012) Volcanic eruptions in the deep sea, ''Oceanography'', 25(1): 142-157. More recently a variety of techniques have been used to study these eruptions with significant developments being made since 1990. These include the use of remote controlled submersibles which can conduct surveys of the ocean floor. The use of hydrophone networks allows volcanic eruptions to be detected.
NOAA (2013) ''Recent Submarine Volcanic Eruptions''. Submersibles can be sent out in response to this to record the result of the eruption. Other tools have included

seismic Seismology (; from Ancient Greek σεισμός (''seismós'') meaning "earthquake" and -λογία (''-logía'') meaning "study of") is the scientific study of earthquakes and the propagation of elastic waves through the Earth or through other ...

signals, acoustic waves and high resolution UAV multibeam mapping. Increasingly, eruptions at greater depths can be observed. For example, an explosive eruption at

West Mata West Mata, located in the far northern portion of Tonga, is an active submarine volcano. Known for the deepest recorded volcanic eruption to date, West Mata does not have a very long recorded history since it was recently discovered in 2008 along ...

in Lau Basin at a depth of 1200 m was studied using submersibles.
Livescience (2011) ''Explosive Underwater Eruptions Are Deepest Yet Seen''

Controls on eruptive style

There is much variation in the style of submarine eruptions. This changes with a number of variables including magma

viscosity The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water. Viscosity quantifies the int ...

, water depth, effusion rate and volatile content. Many studies highlight the effects of

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country a ...

which increases with depth. It is believed that increased pressure restricts the release of volatile gases, resulting in effusive eruptions.Fransis, P. (1993) ''Volcanoes: A Planetary Perspective'', Oxford University Press. This is not to say that explosive eruptions do not occur at depth, just that a higher volatile content is required. It has been estimated that at 500 m explosive activity associated with basalts is suppressed, while depths greater than 2300 m would be sufficient to prevent the majority of explosive activity from

rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals ( phenocrysts) in an otherwise fine-grained groundmass. The miner ...

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 moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...

Shallow water eruptions

At shallow depths it is common for submarine eruptions to be explosive due to the reaction between volatiles in the magma and water which generates a significant quantity of steam.Head, J.W. and Wilson, L. (2008) Deep submarine pyroclastic eruptions: theory and predicted landforms and deposits, ''Journal of Volcanology and Geothermal Research'', 121: 155-193. These eruptions described as Surtseyan are characterised by large quantities of steam and gas and creating large amounts of

pumice Pumice (), called pumicite in its powdered or dust form, is a volcanic rock that consists of highly vesicular rough-textured volcanic glass, which may or may not contain crystals. It is typically light-colored. Scoria is another vesicular v ...

.
Smithsonian Institution National Museum of Natural History Global Volcanism Program (2013). This activity has occurred in many locations. An example is Fukuto-Okanoba near

Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...

. This activity has been observed for almost a century and causes discoloured water, jets of steam and ash, and pumice is found floating in the surrounding water.
Volcano Discovery (2013) Fukutoku-Okanoba volcano. Shallow eruptions can lead to the creation of islands. The most well known is Surtsey in

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

(1963-1967).Siebert, L., Simkin, T. and Kimberley, P. (2010) ''Volcanoes of the World'', University of California Press. Similar island building activity occurs frequently but these are often short lived. Volatile content is also significant. Magma being transported into the ocean through tunnels may see gases being exsolved before reaching the water and so the eruption is effusive. This has been seen in

Hawaii Hawaii ( ; haw, Hawaii or ) is a state in the Western United States, located in the Pacific Ocean about from the U.S. mainland. It is the only U.S. state outside North America, the only state that is an archipelago, and the only stat ...

Deep water eruption

With increased depth there is greater pressure and it is believed that this results in effusive eruptions.Decker, R. and Decker, B. (1989) ''Volcanoes'', W.H. Freeman and Company, USA. There is a variety of evidence, however, which suggests that explosive, pyroclastic activity can occur at depth. This includes observations of

Pele's hair Pele's hair (closest modern Hawaiian translation: "") is a volcanic glass formation produced from cooled lava stretched into thin strands, usually from lava fountain , lava fountains, lava cascades, or vigorous lava flows. It is named after Pel ...

and evidence of

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

collapse.Wright, I.C. and Gamble, J.A. (1999) Southern Kermadec Submarine caldera arc volcanoes (South West Pacific): caldera formation by effusive and pyroclastic eruption, Marine Geology, 161:207-277 This activity is thought to be common at subduction zones due to recycling of the

lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years ...

. It is not exclusive to these plate margins, occurring at

hotspots Hotspot, Hot Spot or Hot spot may refer to: Places * Hot Spot, Kentucky, a community in the United States Arts, entertainment, and media Fictional entities * Hot Spot (comics), a name for the DC Comics character Isaiah Crockett * Hot Spot (Tra ...

and ocean ridges. An example is Kamaʻehuakanaloa (formerly Loihi) near Hawaii where both effusive and explosive activity occurs at 2000 m depth. Two formations associated with submarine eruptions are

seamounts A seamount is a large geologic landform that rises from the ocean floor that does not reach to the water's surface (sea level), and thus is not an island, islet or cliff-rock. Seamounts are typically formed from extinct volcanoes that rise abru ...

and pillow lavas. Pillow lavas are created due to rapid cooling of lava which forms a skin. As more magma is forced into this the skin expands creating a lobe. When this fractures then lava seeps through the gap exposing hot lava to the water and again a skin forms over this: this process is then repeated.

References

External links