Lava dome

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Rhyolitic lava dome of Chaiten Volcano during its 2008-2010 eruption Volcan Chaiten-Sam Beebe-Ecotrust.jpg
Rhyolitic lava dome of Chaitén Volcano during its 2008–2010 eruption
One of the Mono Craters, an example of a rhyolite dome Mono Crater closeup-1000px.jpeg
One of the Mono Craters, an example of a rhyolite dome
Nea Kameni seen from Thera, Santorini Nea Kameni.jpg
Nea Kameni seen from Thera, Santorini

In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. [1] Around 6% of eruptions on earth are lava dome forming. [1] The geochemistry of lava domes can vary from basalt (e.g. Semeru, 1946) to rhyolite (e.g. Chaiten, 2010) although the majority are of intermediate composition (such as Santiaguito, dacite-andesite, present day) [2] The characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways: by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the preserved domes have high silica content and consist of rhyolite or dacite.

Contents

Existence of lava domes has been suggested for some domed structures on the Moon, Venus, and Mars, [1] e.g. the Martian surface in the western part of Arcadia Planitia and within Terra Sirenum. [3] [4]

Dome dynamics

Lava domes in the crater of Mount St. Helens MSH06 aerial crater from north high angle 09-12-06.jpg
Lava domes in the crater of Mount St. Helens

Lava domes evolve unpredictably, due to non-linear dynamics caused by crystallization and outgassing of the highly viscous lava in the dome's conduit. [5] Domes undergo various processes such as growth, collapse, solidification and erosion.

Lava domes grow by endogenic dome growth or exogenic dome growth. The former implies the enlargement of a lava dome due to the influx of magma into the dome interior, and the latter refers to discrete lobes of lava emplaced upon the surface of the dome. [2] It is the high viscosity of the lava that prevents it from flowing far from the vent from which it extrudes, creating a dome-like shape of sticky lava that then cools slowly in-situ. Spines and lava flows are common extrusive products of lava domes. [1] Domes may reach heights of several hundred meters, and can grow slowly and steadily for months (e.g. Unzen volcano), years (e.g. Soufrière Hills volcano), or even centuries (e.g. Mount Merapi volcano). The sides of these structures are composed of unstable rock debris. Due to the intermittent buildup of gas pressure, erupting domes can often experience episodes of explosive eruption over time. If part of a lava dome collapses and exposes pressurized magma, pyroclastic flows can be produced. [6] Other hazards associated with lava domes are the destruction of property from lava flow s, forest fires, and lahars triggered from re-mobilization of loose ash and debris. Lava domes are one of the principal structural features of many stratovolcanoes worldwide. Lava domes are prone to unusually dangerous explosions since they can contain rhyolitic silica-rich lava.

Characteristics of lava dome eruptions include shallow, long-period and hybrid seismicity, which is attributed to excess fluid pressures in the contributing vent chamber. Other characteristics of lava domes include their hemispherical dome shape, cycles of dome growth over long periods, and sudden onsets of violent explosive activity. [7] The average rate of dome growth may be used as a rough indicator of magma supply, but it shows no systematic relationship to the timing or characteristics of lava dome explosions. [8]

Gravitational collapse of a lava dome can produce a block and ash flow. [9]

Cryptodomes

The bulging cryptodome of Mt. St. Helens on April 27, 1980 MSH80 bulge on north side 04-27-80.jpg
The bulging cryptodome of Mt. St. Helens on April 27, 1980

A cryptodome (from Greek κρυπτός, kryptos, "hidden, secret") is a dome-shaped structure created by accumulation of viscous magma at a shallow depth. [10] One example of a cryptodome was in the May 1980 eruption of Mount St. Helens, where the explosive eruption began after a landslide caused the side of the volcano to fall, leading to explosive decompression of the subterranean cryptodome. [11]

Lava spine/Lava spire

Soufriere Hills lava spine before the 1997 eruption Soufriere Hills Lava Dome Spire1.jpg
Soufrière Hills lava spine before the 1997 eruption

A lava spine or lava spire is a growth that can form on the top of a lava dome. A lava spine can increase the instability of the underlying lava dome. A recent example of a lava spine is the spine formed in 1997 at the Soufrière Hills Volcano on Montserrat.

Lava coulées

Chao dacite coulee flow-domes (left center), northern Chile, viewed from Landsat 8 Chao dacite domes.jpg
Chao dacite coulée flow-domes (left center), northern Chile, viewed from Landsat 8

Coulées (or coulees) are lava domes that have experienced some flow away from their original position, thus resembling both lava domes and lava flows. [2]

The world's largest known dacite flow is the Chao dacite dome complex, a huge coulée flow-dome between two volcanoes in northern Chile. This flow is over 14 kilometres (8.7 mi) long, has obvious flow features like pressure ridges, and a flow front 400 metres (1,300 ft) tall (the dark scalloped line at lower left). [12] There is another prominent coulée flow on the flank of Llullaillaco volcano, in Argentina, [13] and other examples in the Andes.

Examples of lava domes

Lava domes
Name of lava domeCountryVolcanic areaCompositionLast eruption
or growth episode
Chaitén lava dome Chile Southern Volcanic Zone Rhyolite 2009
Ciomadul lava domes Romania Carpathians Dacite Pleistocene
Cordón Caulle lava domesChileSouthern Volcanic Zone Rhyodacite to Rhyolite Holocene
Galeras lava dome Colombia Northern Volcanic Zone Unknown2010
Katla lava dome Iceland Iceland hotspot Rhyolite1999 onwards [14]
Lassen Peak United States Cascade Volcanic Arc Dacite1917
Bridge River Vent lava domeCanadaCascade Volcanic ArcDaciteca. 300 BC
Mount Merapi lava dome Indonesia Sunda Arc Unknown2010
Nea Kameni Greece South Aegean Volcanic Arc Dacite1950
Novarupta lava dome Alaska (United States) Aleutian Arc Rhyolite1912
Nevados de Chillán lava domesChileSouthern Volcanic ZoneDacite1986
Puy de Dôme France Chaîne des Puys Trachyte ca. 5760 BC
Santa María lava dome Guatemala Central America Volcanic Arc Dacite2009
Sollipulli lava domeChileSouthern Volcanic Zone Andesite to Dacite1240 ± 50 years
Soufrière Hills lava dome Montserrat Lesser Antilles Andesite2009
Mount St. Helens lava domesUnited StatesCascade Volcanic ArcDacite2008
Torfajökull lava domeIceland Iceland hotspot Rhyolite1477
Tata Sabaya lava domes Bolivia Andes Unknown~ Holocene
Tate-iwaJapan Japan Arc Dacite Miocene [15]
Valles lava domes United States Jemez Mountains Rhyolite50,000-60,000 BP
Wizard Island lava domeUnited StatesCascade Volcanic ArcRhyodacite [16] 2850 BC

Related Research Articles

Volcano rupture in the crust of a planetary-mass object that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface

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.

Stratovolcano Tall, conical volcano built up by many layers of hardened lava and other ejecta

A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).

Dacite Volcanic rock intermediate in composition between andesite and rhyolite

Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The word dacite comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described.

Extrusive rock

Extrusive rock refers to the mode of igneous volcanic rock formation in which hot magma from inside the Earth flows out (extrudes) onto the surface as lava or explodes violently into the atmosphere to fall back as pyroclastics or tuff. In contrast, intrusive rock refers to rocks formed by magma which cools below the surface.

Geology of the Lassen volcanic area

The geology of the Lassen volcanic area presents a record of sedimentation and volcanic activity in the area in and around Lassen Volcanic National Park in Northern California, U.S. The park is located in the southernmost part of the Cascade Mountain Range in the Pacific Northwest region of the United States. Pacific Oceanic tectonic plates have plunged below the North American Plate in this part of North America for hundreds of millions of years. Heat from these subducting plates has fed scores of volcanoes in California, Oregon, Washington and British Columbia over at least the past 30 million years and is also responsible for activities in the Lassen volcanic area.

Santa María (volcano) mountain

Santa María Volcano is a large active volcano in the western highlands of Guatemala, in the Quetzaltenango Department near the city of Quetzaltenango.

Parinacota (volcano) Volcano on the border of Chile and Bolivia

Parinacota, Parina Quta or Parinaquta is a dormant stratovolcano on the border of Chile and Bolivia. Together with Pomerape it forms the Nevados de Payachata volcanic chain. Part of the Central Volcanic Zone of the Andes, its summit reaches an elevation of 6,380 metres (20,930 ft) above sea level. The symmetrical cone is capped by a summit crater with widths of 1 kilometre (0.62 mi) or 500 metres (1,600 ft). Farther down on the southern slopes lie three parasitic centres known as the Ajata cones. These cones have generated lava flows. The volcano overlies a platform formed by lava domes and andesitic lava flows.

Volcanogenic lake

A volcanogenic lake is a lake formed as a result of volcanic activity. They are generally a body of water inside an inactive volcanic crater but can also be large volumes of molten lava within an active volcanic crater and waterbodies constrained by lava flows, pyroclastic flows or lahars in valley systems. The term volcanic lake is also used to describe volcanogenic lakes, although it is more commonly assigned to those inside volcanic craters.

Vulcanian eruption type of volcanic eruption

A Vulcanian eruption is a type of volcanic eruption characterized by a dense cloud of ash-laden gas exploding from the crater and rising high above the peak. They usually commence with phreatomagmatic eruptions which can be extremely noisy due the rising magma heating water in the ground. This is usually followed by the explosive clearing of the vent and the eruption column is dirty grey to black as old weathered rocks are blasted out of the vent. As the vent clears, further ash clouds become grey-white and creamy in colour, with convolutions of the ash similar to those of Plinian eruptions.

La Garita Caldera supervolcanic caldera

La Garita Caldera is a large supervolcanic caldera in the San Juan volcanic field in the San Juan Mountains near the town of Creede in southwestern Colorado, United States. It is west of La Garita, Colorado. The eruption that created the La Garita Caldera is among the largest known volcanic eruptions in Earth's history, as well as being one of the most powerful known supervolcanic events.

Effusive eruption Type of volcanic eruption in which lava steadily flows

An effusive eruption is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground. There are two major groupings of eruptions: effusive and explosive. Effusive eruption differs from explosive eruption, wherein magma is violently fragmented and rapidly expelled from a volcano. Effusive eruptions are most common in basaltic magmas, but they also occur in intermediate and felsic magmas. These eruptions form lava flows and lava domes, each of which vary in shape, length, and width. Deep in the crust, gasses are dissolved into the magma because of high pressures, but upon ascent and eruption, pressure drops rapidly, and these gasses begin to exsolve out of the melt. A volcanic eruption is effusive when the erupting magma is volatile poor, which suppresses fragmentation, creating an oozing magma which spills out of the volcanic vent and out into the surrounding area. The shape of effusive lava flows is governed by the type of lava, rate and duration of eruption, and topography of the surrounding landscape.

Explosive eruption Type of volcanic eruption in which lava is violently expelled

In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a viscous magma such that expelled lava violently froths into volcanic ash when pressure is suddenly lowered at the vent. Sometimes a lava plug will block the conduit to the summit, and when this occurs, eruptions are more violent. Explosive eruptions can send rocks, dust, gas and pyroclastic material up to 20 km (12 mi) into the atmosphere at a rate of up to 100,000 tonnes per second, traveling at several hundred meters per second. This cloud may then collapse, creating a fast-moving pyroclastic flow of hot volcanic matter.

Types of volcanic eruptions Basic mechanisms of eruption and variations

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 mountain shared by Bolivia and Chile

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.

Phreatomagmatic eruption Volcanic eruption involving both steam and magma

Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions contain juvenile (magmatic) clasts. It is common for a large explosive eruption to have magmatic and phreatomagmatic components.

Silverthrone Caldera Stratovolcano in Canada

The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over 350 kilometres (220 mi) northwest of the city of Vancouver and about 50 kilometres (31 mi) west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in western Canada, measuring about 30 kilometres (19 mi) long (north-south) and 20 kilometres (12 mi) wide (east-west). Mount Silverthrone, an eroded lava dome on the caldera's northern flank that is 2,864 metres (9,396 ft) high, may be the highest volcano in Canada.

Mount Edziza volcanic complex mountain in Canada

The Mount Edziza volcanic complex is a large and potentially active north-south trending complex volcano in Stikine Country, northwestern British Columbia, Canada, located 38 kilometres (24 mi) southeast of the small community of Telegraph Creek. It occupies the southeastern portion of the Tahltan Highland, an upland area of plateau and lower mountain ranges, lying east of the Boundary Ranges and south of the Inklin River, which is the east fork of the Taku River. As a volcanic complex, it consists of many types of volcanoes, including shield volcanoes, calderas, lava domes, stratovolcanoes, and cinder cones.

Lava Molten rock expelled by a volcano during an eruption

Lava is molten rock generated by geothermal energy and expelled through fractures in planetary crust or in an eruption, usually at temperatures from 700 to 1,200 °C. The structures resulting from subsequent solidification and cooling are also sometimes described as lava. The molten rock is formed in the interior of some planets, including Earth, and some of their satellites, though such material located below the crust is referred to by other terms.

Ceboruco volcano in central western Mexico

Ceboruco is a dacitic stratovolcano located in Nayarit, Mexico, northwest of the Trans-Mexican Volcanic Belt. The largest eruption, the Jala Plinian eruption, was around 930 AD ±200, VEI 6, releasing 11 cubic kilometres (2.6 cu mi) of tephra. The most recent and best documented eruption from Ceboruco lasted from 1870–1875, with fumarole activity lasting well into the 20th century. The mountain features one large caldera, created during the Jala eruption, with a smaller crater nested inside that formed when the Dos Equis lava dome collapsed during the Coapales eruption around 1100 AD. Within both of these craters, are several explosive volcanic features, including scoria deposits, lava domes, and pyroclastic domes, or cinder cone volcanoes.

Archean felsic volcanic rocks

Archean felsic volcanic rocks are felsic volcanic rocks that were formed in the Archean Eon. The term "felsic" means that the rocks have silica content of 62–78%. Given that the Earth formed at ~4.5 billion year ago, Archean felsic volcanic rocks provide clues on the Earth's first volcanic activities on the Earth's surface started 500 million years after the Earth's formation.

References

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  14. Eyjafjallajökull and Katla: restless neighbours
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  16. Map of Post-Caldera Volcanism and Crater Lake USGS Cascades Volcano Observatory. Retrieved 2014-01-31.