Submarine volcano
A submarine volcano is a fissure in the earth's crust that is below the ocean surface and through which magma penetrates to the surface.
The submarine, i.e. undersea, volcanoes are on the one hand the most common volcanoes on earth . On the other hand, due to their location, which can be up to several thousand meters below the sea surface, they are also the ones that are generally still the least studied.
Submarine volcanoes on mid-ocean ridges are estimated to be responsible for 75% of the Earth's annual magma output. On the ocean ridges, such as the Mid-Atlantic Ridge, there are also a particularly large number of crevice volcanoes that tend to have more effusive eruptions .
Most of these volcanoes are located deep below the sea surface, but some are relatively close to it and could endanger neighboring populated areas in the event of an eruption due to gas and ash emissions.
Formation of a submarine volcano
The magmas form at the boundary between the earth's mantle and the earth's crust, which is about 10 km deep in the ocean. The movements of the continental plates mean that in certain places the earth's crust is particularly thin and furrowed by crevices. This applies above all to the ocean ridges such as the Mid-Atlantic Ridge, where two plates drift apart, but also to the subduction zones , as one can e.g. B. found at the Pacific Ring of Fire , where one plate slides under another. Also hot spots , which are independent of plate shifts, causing volcanic eruptions in the sea, as one example. B. can be observed in the Hawaiian Islands.
At these points it is especially easy for magmas to ascend. These infiltrate into other layers and initially form intrusions on which the actual volcanoes are built. Due to the rapid cooling by the approximately 1 to 2 ° cold sea water as well as the strong pressure, a considerable part of the ejected lavas takes on tubular shape. They are pillow lavas . In the center of the submarine volcanoes, as in those on the surface of the earth, one finds a large number of conveyor tunnels and one to several magma chambers . Through this the magma rises to the surface and gas bubbles form in it as the pressure decreases. These in turn cause explosive underwater eruptions at depths of around 1000 m below the sea surface to just below it. This creates pyroclastic materials, but also fine to finest glass particles, which in turn represent the volcano's slopes, which are quite at risk of erosion. This composition of very loose material explains the frequency of landslides on submarine volcanoes and also ocean islands, such as in Tenerife .
Types of submarine volcanoes
Seamount
Most submarine volcanoes are called seamounts . They are the most common type of volcano on earth, with over a million in the Pacific alone . They are mostly found near mid-ocean ridges and subduction zones, where they can create obstacles for the plates to stick to, causing violent earthquakes.
Seamounts that are close to the mid-ocean ridges preferentially promote lavas of tholeiitic composition, the further away they are from the ridges, the more alkaline lavas are produced.
Guyot
A guyot is a special type of seamount. You can recognize it by its truncated cone shape.
They are former seamounts that have been deformed by erosion and are often covered with fossil coral reefs . Some of them have also received their special shape through the formation of a caldera .
Ocean islands
Only in cases where the eruption rate far exceeds that of erosion can ocean islands eventually form, as is the case e.g. B. observed from 1963 in the case of Surtsey .
Exploration of submarine volcanoes
Eruptions and potential hazards
Research into submarine volcanoes is expensive and time-consuming.
They are often not easy to discover. That is u. a. that their eruptions are dampened. The thermal conductivity of the water causes a rapid cooling of the ejected materials, so that the magma turns into volcanic glass much faster than in the air . Depending on the depth of the water surface above them, the pressure on them increases. This significantly dampens the explosiveness of the eruption, making the eruptions all the more difficult to detect as the water depth increases.
Research examples
Mediterranean Sea
Columbus volcano
A historical example of the surprising discovery of a submarine volcano is the Columbos volcano in the Aegean Sea . It was discovered in 1650 when an explosive eruption of Columbos killed 70 people in Santorini .
Empedocles volcano
Another example is the Empedocles volcano on the Strait of Sicily . It was only discovered in 2006, while the former island of Ferdinandea , which belongs to the same volcanic complex, has been known since 1831.
Tyrrhenian Sea
In Italy , further investigations into submarine volcanoes in the Tyrrhenian Sea are planned , e.g. B. the Marsili , among other things because of possible flank collapse and their tsunami potential.
In 2006 an American expedition found traces of lead that could be traced as far as Australia on the underwater volcano Marsili, around 350 km off the west coast of Italy .
Atlantic
Iceland
In Iceland we are interested in the north and southwest of Iceland for the submarine continuations of the Mid-Atlantic Ridge. In addition to the Tjörnes fracture zone and the Kolbeinseyrücken in the north of the island, this applies above all to the Reykjanesrück , the part off Iceland in the south. For example, in 2007 a large active submarine volcano was discovered there about 50 km from the main island, which was called Njörður .
Deepest black smokers in the Cayman Trench
A British research expedition used remote-controlled robotic submersibles to discover the deepest black smokers found so far. They are located near the Cayman Islands in the Cayman Trench at a depth of 5000 m.
The expedition with the ship RRS James Cook is part of a project funded by the UK Natural Environment Research Council , which began on March 21, 2010 in Trinidad .
Gakkel back 85 ° E
A noticeable accumulation of strong earthquakes (up to over 5 on the Richter scale) was noted in 1999 on the so-called Gakkel Ridge , the arctic continuation of the Mid-Atlantic Ridge between Siberia and Greenland . There were 200 earthquakes of this magnitude within 7 months. The SCICEX expedition checked the area twice in time and discovered fresh lava flows on a submarine volcano at 85 ° E. The event aroused the interest of geoscientists not least because of the long period over which it took place. Previous findings confirmed submarine eruptions only for periods of up to around four weeks.
The Amore 2001 expedition of the Alfred Wegener Institute was able to prove current eruptive activity in 2001 through tremor measurements and recordings of explosion noises on the sea floor near the same volcanic complex. Another international expedition to the same volcanic complex in 2007 collected more accurate data.
Pacific
Japan
An undersea volcano called Fukutoku-Okanoba erupted on July 2, 2005 off the Japanese coast about 1,300 km from Tokyo . The volcano was known for regular eruptions in the 20th century, most recently in 1992. It also succeeded in forming an island in 1986, which only existed for a short time before it was eroded by the sea.
Eruption of a submarine volcano near Tonga
An explosive eruption occurred around March 17, 2009 on a submarine volcano near the island of Tonga in the Pacific, about 10 km from the main island of Tongatapu . In the eruption, which u. a. pyroclastic currents produced a new island.
Mapping in front of Kamchatka
In 2009 a German-Russian research team under the scientific direction of the Federal Institute for Geosciences and Natural Resources (BGR) succeeded in measuring 2700 km of the seabed around the submarine volcanoes of the Emperor Seamount chain off the Russian peninsula of Kamchatka . The expedition in the Northwest Pacific on the German research vessel "Sonne" lasted three weeks.
The extinct volcanoes rise up to 4,500 meters above the sea floor. The elastic crust bends under them. The scientists found a 700 km long fracture zone. A height difference of 1000 m between the slabs was found at the edge of the demolition. The volcanoes that originally in the area of Hawaii had formed -Archipels are, with the Pacific Plate moved northwest to Kamchatka and dive there slowly under the North American Plate from, being a decisive influence on the geology of the Kamchatka Peninsula, the earthquake and engage in volcanic activity.
Development of a submarine volcano and its surroundings in the Mariana Islands
In the Mariana Islands in the Pacific, an international team of researchers led by Oregon State University followed the development of a submarine volcano they named NW Rota-1 . The volcano, located about 520 m below the sea surface, was discovered in 2004 and observed more closely in 2006. The volcano seems to be in constant action and in the meantime had built a 40 m high and 300 m wide crater. An underwater microphone had provided evidence of the constant breakout activity.
Scientists also examined the fauna present on the volcano and discovered some new species . It was also noticeable that with increased activity, the surroundings of the mountain apparently became more attractive to the animals such as B. crabs , prawns , snails and barnacles worked. The animals feed on bacteria that settle on the volcanic vent. They are adapted to living conditions that would be toxic to others .
One of the shrimp species, a previously unknown species, becomes a predator and scavenger in adulthood. a. fed on other shrimp species and fish killed by the volcano.
Loihi, the next Hawaiian island?
The submarine volcano Loihi lies above the hot spot of Hawaii and will probably form the next island there. This will take a while, however, as the summit of the submarine mountain is currently around 1000 m below the sea surface.
The state American research institute NOAA has examined the volcano in detail. It maintains a specialized underwater research center in Hawaii.
It turned out that the volcano has three summit craters. Numerous hydrothermal vents can be found on the walls of the youngest crater, which formed in 1996. The water-gas mixture flowing out of them is up to 200 ° hot.
See also
literature
- Hans Ulrich Schmincke: Vulcanism. Scientific Book Society, Darmstadt 2000, ISBN 3-534-14102-4 .
Web links
Photos and videos
- Video of a submarine eruption near Japan with explanations - NOAA project (English)
- Video of a submarine volcanic eruption in the Pacific (accessed October 31, 2011)
- Research vessel "Nautilus", Project Mediterranean 2011 (with videos, English)
Scientific contributions
- Anthony B. Watts: Research: The deep structure of oceanic islands and seamounts. Author's website.
- Deep-sea volcanoes don't just produce lava flows, they also explode. on phys.org.
- Richard Smith, David J. Lowe and Ian Wright: Volcanoes - The Kermadec Ridge: submarine volcanoes. The Encyclopedia of New Zealand (English)
- V. Paoletti et al .: Magnetic signature of submarine volcanoes in the Phlegrean Fields-Ischia Ridge (North-Western side of the Bay of Naples, Southern Italy). In: Annals of Geophysics , Vol. 51, No. 4, August 2008.
- Steven Carey, Haraldur Sigurdsson: Exploring submarine Arc volcanoes. Special issue on Ocean Exploration. In: Oceanography , Vol. 20, No. 4, December 2007, doi : 10.5670 / oceanog.2007.08 .
- A. Klügel et al .: Fluid venting at Cretaceous seamount, Canary Archypelago. Goldschmidt Conference Abstracts, 2007 (on a seamount at El Hierro).
- Robert W. Embley et al .: Long-term eruptive activity at a submarine arc volcano. In: Nature , Letters, Vol. 441, May 25, 2006.
- Intro to Hydrothermal Activity and Event Plumes (aka Megaplumes) from Submarine Eruptions. Lecture, School of Ocean and Earth Science and Technology, Hawaii, Fall 2011 (Introduction to hydrothermal phenomena and plumes from submarine eruptions).
- RP Dziak et al .: Observations of regional seismicity and local harmonic tremor at Brothers volcano, south Kermadec arc, using an ocean bottom hydrophone array. In: Journal of Geophysical Research , Vol. 113, 2008, doi : 10.1029 / 2007JB005533 .
- Sharon R. Allen, Jocelyn McPhie: Products of neptunian eruptions. In: Geology , Vol. 37, No. 7, pp. 639-642, doi : 10.1130 / G30007A.1 .
- Erik Klemetti: Hydrovolcanism: When Magma and Water Mix. Wired Science blogs, November 11, 2011.
- Anthony B. Watts et al .: Rapid rates of growth and collapse of Monowai submarine volcano in the Kermadec Arc. In: Nature Geoscience , No. 5, 2012, pp. 510-15.
Press reports
- D. Shukman: Rise and fall of underwater volcano revealed , BBC News, May 13, 2012
- D. Shukman: Undersea mountains march into abyss , BBC News, December 5, 2011 (with video)
- M. Field et al .: 25-000-sq-km-sea-of-pumice-floats-off-New-Zealand on stuff.co.nz, August 10, 2012 (English)
Individual evidence
- ↑ FAQ ( Memento from June 26, 2014 in the Internet Archive ) on volcano.si.edu
- ↑ Hans Ulrich Schmincke: Vulcanism. P. 86.
- ↑ Hans Ulrich Schmincke: Vulcanism. P. 17.
- ↑ cf. Hans Ulrich Schmincke: Vulcanism. P. 68: "If magma [...] rises at certain points in the earth's crust through the often much older ocean crust and the young sediments above it [...], it will presumably penetrate the sediments laterally and form a complex of intrusive rocks on which the actual submarine volcano is growing. This will mainly consist of pillow lava units. "
- ↑ a b Hans Ulrich Schmincke: Vulkanismus. P. 65.
- ↑ a b Hans Ulrich Schmincke: Vulkanismus. P. 67.
- ↑ cf. F. Caratori Tontini et al .: Potential-field modeling of collapse-prone submarine volcanoes in the southern Tyrrhenian Sea (Italy). In: Geophysical Research Letters , Vol. 37, 2010, doi : 10.1029 / 2009GL041757 ( Abstract ( Memento from November 27, 2012 in the Internet Archive )).
- ↑ At An Underwater Volcano, Evidence Of Man's Environmental Impact. at ScienceDaily
- ↑ cf. including: Giant Undersea Volcano Found Off Iceland on nationalgeographic.com
- ↑ World's deepest known undersea volcanic vents discovered on sciencedaily.com. See also: National Oceanographic Center, Southampton ( Memento of the original from March 4, 2016 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. .
- ↑ Ultra-slow mid-ocean ridges. Website of the Alfred Wegener Institute , accessed on November 10, 2017.
- ↑ Fukutoku-Okanoba volcano on volcanodiscovery.com, accessed on May 24, 2015
- ↑ cf. Global Volcanism Program of the Smithsonian Institute : http://www.volcano.si.edu/volcano.cfm?vn=243040&vtab=Eruptions
- ↑ BGR press release of June 24, 2009, accessed on August 11, 2012.
- ↑ Erupting Undersea Volcano Near Island Of Guam Supports Unique Ecosystem on sciencedaily.com
- ↑ see: Alexander Malahoff: Loihi Submarine Volcano: A unique, natural extremophile laboratory on nurp.noaa.gov, accessed on May 24, 2010.
