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.<ref name=":0">Template:Cite book</ref> Around 6% of eruptions on Earth form lava domes.<ref name=":0" /> 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).<ref name=eov>Template:Cite encyclopedia</ref> 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.
Existence of lava domes has been suggested for some domed structures on the Moon, Venus, and Mars,<ref name=":0" /> e.g. the Martian surface in the western part of Arcadia Planitia and within Terra Sirenum.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>
Dome dynamicsEdit
Lava domes evolve unpredictably, due to non-linear dynamics caused by crystallization and outgassing of the highly viscous lava in the dome's conduit.<ref>Template:Citation</ref> Domes undergo various processes such as growth, collapse, solidification and erosion.<ref>Template:Cite journal</ref>
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.<ref name=eov /> 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.<ref>Template:Cite journal</ref> Spines and lava flows are common extrusive products of lava domes.<ref name=":0" /> 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.<ref>Template:Cite journal</ref> If part of a lava dome collapses and exposes pressurized magma, pyroclastic flows can be produced.<ref>Template:Citation</ref> Other hazards associated with lava domes are the destruction of property from lava flows, 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.<ref>Template:Citation</ref> 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.<ref>Template:Citation</ref>
Gravitational collapse of a lava dome can produce a block and ash flow.<ref name=encyclovolc2015>Template:Cite book</ref>
Related landformsEdit
CryptodomesEdit
A cryptodome (from the Greek {{#invoke:Lang|lang}}, Template:Transliteration, "hidden, secret") is a dome-shaped structure created by accumulation of viscous magma at a shallow depth.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Two examples of cryptodomes were the ones leading to the 1956 eruption of Bezymianny and the 1980 eruption of Mount St. Helens. In each case, the explosive eruption began after the cryptodome caused the side of the volcano to bulge outward and led to a sector collapse, in turn leading to explosive decompression of the subterranean cryptodome.<ref name="CVOMountStHelens">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name="Donnadieu_etal_2001">Template:Cite journal</ref>
Lava spine/Lava spireEdit
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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 couléesEdit
Coulées (or coulees) are lava domes that have experienced some flow away from their original position, thus resembling both lava domes and lava flows.<ref name="eov" />
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 Template:Convert long, has obvious flow features like pressure ridges, and a flow front Template:Convert tall (the dark scalloped line at lower left).<ref>Chao dacite dome complex at NASA Earth Observatory</ref> There is another prominent coulée flow on the flank of Llullaillaco volcano, in Argentina,<ref>Coulées! by Erik Klemetti, an assistant professor of Geosciences at Denison University.</ref> and other examples in the Andes.
Examples of lava domesEdit
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| Name of lava dome | Country | Volcanic area | Composition | Last eruption or growth episode | |
|---|---|---|---|---|---|
| Chaitén lava dome | Chile | Southern Volcanic Zone | Rhyolite | 2009 | |
| Ciomadul lava domes | Romania | Carpathians | Dacite | Pleistocene | |
| Cordón Caulle lava domes | Chile | Southern Volcanic Zone | Rhyodacite to Rhyolite | Holocene | |
| Galeras lava dome | Colombia | Northern Volcanic Zone | Unknown | 2010 | |
| Katla lava dome | Iceland | Iceland hotspot | Rhyolite | 1999 onwards<ref>Eyjafjallajökull and Katla: restless neighbours</ref>Template:Better source needed | |
| Lassen Peak | United States | Cascade Volcanic Arc | Dacite | 1917 | |
| Black Butte (Siskiyou County, California) | United States | Cascade Volcanic Arc | Dacite | citation | CitationClass=web
}}</ref> |
| Bridge River Vent lava dome | Canada | Cascade Volcanic Arc | Dacite | ca. 300 BC | |
| La Soufrière lava dome | Saint Vincent and the Grenadines | Lesser Antilles Volcanic Arc | citation | CitationClass=web
}}</ref> | |
| Mount Merapi lava dome | Indonesia | Sunda Arc | Unknown | 2010 | |
| Nea Kameni | Greece | South Aegean Volcanic Arc | Dacite | 1950 | |
| Novarupta lava dome | United States | Aleutian Arc | Rhyolite | 1912 | |
| Nevados de Chillán lava domes | Chile | Southern Volcanic Zone | Dacite | 1986 | |
| Puy de Dôme | France | Chaîne des Puys | Trachyte | Template:Circa | |
| Santa María lava dome | Guatemala | Central America Volcanic Arc | Dacite | 2009 | |
| Sollipulli lava dome | Chile | Southern Volcanic Zone | Andesite to Dacite | 1240 ± 50 years | |
| Soufrière Hills lava dome | Montserrat | Lesser Antilles | Andesite | 2009 | |
| Mount St. Helens lava domes | United States | Cascade Volcanic Arc | Dacite | 2008 | |
| Torfajökull lava dome | Iceland | Iceland hotspot | Rhyolite | 1477 | |
| Tata Sabaya lava domes | Bolivia | Andes | Unknown | ~ Holocene | |
| Tate-iwa | Japan | Japan Arc | Dacite | Miocene<ref>Template:Cite journal</ref> | |
| Tatun lava domes | Taiwan | Andesite | citation | CitationClass=web
}}</ref> | |
| Valles lava domes | United States | Jemez Mountains | Rhyolite | 50,000-60,000 BP | |
| Wizard Island lava dome | United States | Cascade Volcanic Arc | Rhyodacite<ref>Map of Post-Caldera Volcanism and Crater Lake Template:Webarchive USGS Cascades Volcano Observatory. Retrieved 2014-01-31.</ref> | 2850 BC |
ReferencesEdit
External linksEdit
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