A lava balloon is a gas-filled bubble of lava that floats on the sea surface. It can be up to several metres in size. When it emerges from the sea, it is usually hot and often steaming. After floating for some time it fills with water and sinks again.
Lava balloons can form in lava flows entering the sea and at volcanic vents, but they are not common. They have been observed in the Azores, Canary Islands, Hawaii, Japan, Mariana Islands and Mexico. Apparently, they are generated when gases trapped within magma form large bubbles that eventually rise to the sea surface. In the Canary Islands, balloons containing sediments were used to infer the age of the basement on which the volcano is constructed; these sediments were also at first misinterpreted as evidence of an impending large explosive eruption.
Lava balloons are gas-filled bubbles surrounded by a crust formed by lava; [1] their gas content allows them to float on the sea surface. [2] Observed sizes range from 0.3 metres (1 ft 0 in) at El Hierro (Canary Islands) during the 2011–2012 eruption [1] to about 3 metres (9.8 ft) at Terceira on their long axis with rounded shapes. [3] They have one or sometimes several large cavities surrounded by a 3–8-centimetre-thick (1.2–3.1 in) crust. The outer part of the crust is highly vesicular and striated and has delicate flow structures that can be seen using a scanning electron microscope. It is fragile and often breaks off the balloon. The inner part of the crust is separated from the outer part by orange and white layers. It is subdivided into three inward-thickening layers, all of which contain varying amounts of vesicles that become larger toward the interior. [3] Recovered lava balloons and associated rocks are on display in the UGGp museum on El Hierro. [4]
Lava balloons have been described from Terceira Island in the Azores, [3] at Teishi Knoll of Izu-Tobu (Japan) in 1989, [2] El Hierro, offshore Pantelleria (Foerstner volcano, Italy) in 1891 and Kealakekua Bay (Mauna Loa, [5] Hawaii) in 1877. [6] Similar floating scoria blocks containing reticulite [lower-alpha 1] [7] were observed in 1993–1994 at Socorro, Mexico. [3] As of 2012 [update] , lava balloons have been observed only at these sites, [6] although the increasing number of observations might indicate that this is a common mode of submarine volcanism. [2]
A similar style of eruption but involving silicic magmas has also been found and christened "Tangaroan", after the research ship RV Tangaroa that carried out research on the Macauley caldera. [lower-alpha 2] [2] Balloon-like structures were observed in 1934–1935 at Shin-Iwo-jima, Japan, and at West Rota in the Marianas. [9] At Macauley Island in the Kermadec Islands such a style of eruption has been inferred and used to explain the presence of large rocks at substantial distances from the volcanic vent. [8]
Lava balloons observed during a 1998–2000 eruption at Terceira are considered to be the most noteworthy expression of that eruption. [3] They were described as steaming dark objects floating on the sea, hot enough to damage fishing ropes. At first, they were thought to be dead whales or trunks. [3] They surfaced in batches over a span of several months, clustering in particular areas that appear to reflect the position of active volcanic vents on the seafloor but also wind and ocean current driven transport. [3] [5] Sometimes, hundreds of balloons were observed on a given occasion, [6] accompanied by gas bubbles [10] (i.e. gas slug) and particles shed by the balloons, all of which rose through the water in the form of plumes. [11] The balloons steamed at first under their own heat, forming small vapour plumes and hissing sounds. [6] Their insides could reach temperatures of over 900 °C (1,650 °F) [3] and were sometimes incandescent. [12] Balloons usually floated for less than 15 minutes before sinking again as water penetrated them through cracks in the crust and gases escaped. [3] Sometimes, however, explosions threw fragments for tens of meters when water interacted with a hot interior. [3] Remotely operated underwater vehicle (ROV) observations of the putative vent area found debris that may have come from lava balloons. [13]
The Pantelleria eruption generated scoriaceous and vesicular floating structures with sizes exceeding 1 metre (3 ft 3 in) that sank again beneath the water surface after they had become saturated with water. [14] 1892 descriptions of lava balloons about the Pantelleria eruption resemble the Terceira balloons. [15] The eruption was discovered thanks to its balloons. [16] As reported by fishers, black balloons of lava floated on the sea, sometimes propelled by steam jets and sometimes exploding with up to 20 metres (66 ft) high debris fountains. As with Terceira, they were accompanied by gas bubbles [17] and many of them were hot enough to melt zinc. [lower-alpha 3] [18] Water entering the balloons evaporated from the heat, thus delaying their filling. [19] Eventually, the balloons filled with water and sank again. [20]
At El Hierro, lava balloons were erupted from 27 November 2011 until 23 February 2012 [1] and often exploded upon reaching the sea surface. On the seafloor close to the vent were balloons with various shapes including amphora-like and sizes reaching over 4 metres (13 ft). They had sunk to the seafloor immediately after being ejected from the vent and had sometimes spilled magma. The amphora-like shape appears to have formed when floating balloons degassed through vents at their top and the balloons deformed. [21] On the seafloor, the ballons were buried by later pillow lavas. [22]
Towards the end of the eruption, some lava balloons had a thin layer of solidified magma around a glassy core and appeared to float for longer times, allowing them to reach the coast. [6] The balloons were named "restingoliths" [23] and the glassy core "xeno-pumice". [24] Similar balloons were observed at Teishi Knoll and appear to form when sediments are incorporated into lava and melted, forming a pumice-like structure. [2] At El Hierro, the origin of the cores gave rise to a scientific debate about whether they originated as sediment or as silicic magma; now there is agreement that they formed out of sediments. [25] In Socorro, the cores of lava balloons contained reticulite. [15]
In Kealakekua Bay, over a hundred lava balloons were observed. [26] They emitted sulfurous gases [27] and steam and were hot inside, even incandescent. As ships were moving across the area rising balloons in the water impacted their hulls but did not do any damage. [26]
Large floating pumice blocks such as these observed in Kikai, Japan, in 1934–1935 may be comparable to lava balloons, [28] but they are produced by eruptions of felsic magma, which are rich in silicates and lighter elements. [6] By contrast, lava balloons are generally produced by eruptions of alkali basalt, [7] although few basaltic eruptions produce them. [6]
Lava balloons are probably limited to a depth range of 30–1,000 metres (98–3,281 ft): too deep, and gas bubbles do not form; too shallow, and degassing fragments the rocks. Only a few sufficiently large balloons can rise all the way to the sea surface; smaller ones fill quickly with water and sink. [7] Overly crystalline magma may render a crust too brittle to form a lava balloon. [29]
Several different mechanisms have been invoked to explain the genesis of lava balloons. [30] Water that penetrates the lava can boil and the resulting vapours can inflate the balloons and make them float, [15] although for Terceira a non-water gas composition has been inferred. [10] They are usually observed when lava flows enter the sea. They appear to form when water is trapped in lava as it flows onto a beach with waves or enters lava tubes; in the latter case, entrained water can be transported through the tube and eventually end up in developing pillow lavas which are rendered buoyant by water vapour bubbles. [3]
Less commonly, as in Terceira, balloons and accompanying gas bubbles appear to have formed on volcanic vents rather than at the front of lava flows, [3] and more specifically on volcanic vents where magma ponded. [10] There, gas emanating from a gas-rich magma accumulated below a crust on top of lava, forming blisters that eventually reached a critical buoyancy and broke off, forming lava balloons. [3] [lower-alpha 4] The high gas content and low viscosity of the magma during the Terceira eruption allowed balloons to form despite the vents being located at considerable depth. [3]
Finally, lava fountaining processes have been proposed to form balloons underwater. [15] According to this model, slabs of magma in the water are surrounded by a thin shell which traps exoluting gases but also magma. The trapped gases inflate the shell and make it buoyant, while the remnant magma maintains the shell as it expands. [9]
On São Miguel Island in the Azores, lava balloons are considered to be one of the main volcanic hazards stemming from submarine volcanic eruptions. [33] Early lava balloons erupted during the 2011–2012 El Hierro eruption contained xeno-pumice, which raised concerns that evolved [lower-alpha 5] magmas such as phonolite and trachyte, capable of generating explosive eruptions, might be present under the volcano. As the eruption continued, these concerns together with an outburst of gas led to the evacuation of the town of La Restinga. The link between xeno-pumice and evolved magmas was contested early on; [35] when explosive eruptions did not occur, this led to complaints that the response to the eruption had been disproportionate especially given its effect on the economy. [36] The management of the El Hierro eruption in general attracted intense criticism. [37]
At El Hierro, the crevice-rich submarine terrain formed by sunk lava balloons and lava bombs forms a particular habitat. Animal species encountered there include the decapod Plesionika narval . [38]
At El Hierro, foraminifera fossils found in the glassy cores of lava balloons have been inferred to originate from sediments that underlie the El Hierro volcano. These fossils indicate a Cretaceous–Pliocene age for these sediments, implying that El Hierro rests on the youngest sediment base of the archipelago. The progressively lower age of the islands from east to west reinforces the theory that the Canary Islands are on top of a hotspot. [39] Furthermore, it has been proposed that lava balloons might be proof of shallow-water volcanic eruptions. [7]
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.
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Payún Matrú is a shield volcano in the Reserva Provincial La Payunia of the Malargüe Department, south of the Mendoza Province in Argentina. It lies in the back-arc region of the Andean Volcanic Belt, and was formed by the subduction of the Nazca Plate beneath the South American Plate. Payún Matrú, along with the Llancanelo, Nevado and Salado Basin volcanic fields, form the Payenia province. It has been proposed as a World Heritage Site since 2011.
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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 ridges alone are estimated to account for 75% of the magma output on Earth. Although most submarine volcanoes are located in the depths of seas and oceans, some also exist in shallow water, and these can discharge material into the atmosphere during an eruption. The total number of submarine volcanoes is estimated to be over one million of which some 75,000 rise more than 1 kilometre (0.62 mi) above the seabed. Only 119 submarine volcanoes in Earth's oceans and seas are known to have erupted during the last 11,700 years.
Lascar is a stratovolcano in Chile within the Central Volcanic Zone of the Andes, a volcanic arc that spans Peru, Bolivia, Argentina and Chile. It is the most active volcano in the region, with records of eruptions going back to 1848. It is composed of two separate cones with several summit craters. The westernmost crater of the eastern cone is presently active. Volcanic activity is characterized by constant release of volcanic gas and occasional vulcanian eruptions.
Cerro Galán is a caldera in the Catamarca Province of Argentina. It is one of the largest exposed calderas in the world and forms part of the Central Volcanic Zone of the Andes, one of the three volcanic belts found in South America. One of several major caldera systems in the Central Volcanic Zone, the mountain is grouped into the Altiplano–Puna volcanic complex.
Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.
Ollagüe or Ullawi is a massive andesite stratovolcano in the Andes on the border between Bolivia and Chile, within the Antofagasta Region of Chile and the Potosi Department of Bolivia. Part of the Central Volcanic Zone of the Andes, its highest summit is 5,868 metres (19,252 ft) above sea level and features a summit crater that opens to the south. The western rim of the summit crater is formed by a compound of lava domes, the youngest of which features a vigorous fumarole that is visible from afar.
James Healy Seamount is a submarine volcano located among the South Kermadec Ridge Seamounts south of New Zealand's Kermadec Islands. It consists of a volcanic cone that reaches a depth of 1,150 metres (3,770 ft) below sea level, two 2–2.5 kilometres (1.2–1.6 mi) and 1.3 kilometres (0.81 mi) wide calderas and a parasitic cone that reaches a depth of 950 metres (3,120 ft) below sea level. The flanks of the volcano are covered with pumice and volcanic rocks, and hydrothermal venting occurs inside the caldera.
Submarine eruptions are volcano eruptions which take place beneath the surface of water. These occur at constructive margins, subduction zones and within tectonic plates 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.
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or underwater, usually at temperatures from 800 to 1,200 °C. The volcanic rock resulting from subsequent cooling is also often called lava.
La Pacana is a Miocene age caldera in northern Chile's Antofagasta Region. Part of the Central Volcanic Zone of the Andes, it is part of the Altiplano-Puna volcanic complex, a major caldera and silicic ignimbrite volcanic field. This volcanic field is located in remote regions at the Zapaleri tripoint between Chile, Bolivia and Argentina.
The 2011–2012 El Hierro eruption occurred just off the island of El Hierro, the smallest and farthest south and west of the Canary Islands, in the Atlantic Ocean off the coast of Africa. The island is also the youngest in the volcanic chain. The October 2011 – March 2012 eruption was underwater, with a fissure of vents located approximately 2 kilometres to the south of the fishing village of La Restinga on the southern coast of the island. Increased seismicity in June 2012 to the north-west of the vent did not result in another phase of eruptive activity. Until the 2021 La Palma eruption, which started on 19 September 2021, this was the last volcanic eruption in Spain.
Panizos is a Late Miocene caldera in the Potosí Department of Bolivia and the Jujuy Province of Argentina. It is part of the Altiplano-Puna volcanic complex of the Central Volcanic Zone in the Andes. 50 volcanoes active in recent times are found in the Central Volcanic Zone, and several major caldera complexes are situated in the area. The caldera is located in a difficult-to-access part of the Andes.
Tata Sabaya is a 5,430-metre (17,810 ft) high volcano in Bolivia. It is part of the Central Volcanic Zone, one of several volcanic belts in the Andes which are separated by gaps without volcanic activity. This section of the Andes was volcanically active since the Jurassic, with an episode of strong ignimbritic volcanism occurring during the Miocene. Tata Sabaya lies in a thinly populated region north of the Salar de Coipasa salt pan.
Monowai Seamount is a volcanic seamount to the north of New Zealand. It is formed by a large caldera and a volcanic cone just south-southeast from the caldera. The volcanic cone rises to depths of up to 100 metres (330 ft) but its depth varies with ongoing volcanic activity, including sector collapses and the growth of lava domes. The seamount and its volcanism were discovered after 1877, but only in 1980 was it named "Monowai" after a research ship of the same name.
The Honolulu Volcanics are a group of volcanoes which form a volcanic field on the island of Oʻahu, Hawaiʻi, more specifically in that island's southeastern sector and in the city of Honolulu from Pearl Harbor to the Mokapu Peninsula. It is part of the rejuvenated stage of Hawaiian volcanic activity, which occurred after the main stage of volcanic activity that on Oʻahu built the Koʻolau volcano. These volcanoes formed through dominantly explosive eruptions and gave rise to cinder cones, lava flows, tuff cones and volcanic islands. Among these are well known landmarks such as Diamond Head and Punchbowl Crater.
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