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Encyclopedia > Lava
Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary.

Lava is molten rock expelled by a volcano during an eruption. When first extruded from a volcanic vent, it is a liquid at temperatures from 700 °C to 1,200 °C (1,300 °F to 2,200 °F). Although lava is quite viscous, with about 100,000 times the viscosity of water, it can flow great distances before cooling and solidifying. Wikipedia does not have an article with this exact name. ... Wiktionary (a portmanteau of wiki and dictionary) is a multilingual, Web-based project to create a free content dictionary, available in over 150 languages. ... The rocky side of a mountain creek near Orosí, Costa Rica. ... For other uses, see Volcano (disambiguation). ... A liquid will usually assume the shape of its container A liquid is one of the main states of matter. ... Fig. ... Viscosity is a measure of the resistance of a fluid to deform under shear stress. ...


Lava solidifies to form igneous rock. A lava flow is the hardened formation, whereas one still partly molten is an active lava flow. The word 'lava' comes from Italian, and is probably derived from the Latin word labes which means a fall, slide, or sinking in. The first use in connection with extruded magma (molten rock below the earth's surface) was apparently in a short account written by Francesco Serao [1] on the eruption of Vesuvius between May 14 and June 4, 1737. Serao described "a flow of fiery lava" as an analogy to the flow of water and mud down the flanks of the volcano following heavy rain. Volcanic rock on North America Plutonic rock on North America Igneous rocks form when rock (magma) cools and solidifies, with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks. ... Latin is an ancient Indo-European language originally spoken in Latium, the region immediately surrounding Rome. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Mount Vesuvius (Italian: Monte Vesuvio) is a volcano east of Naples, Italy, located at 40°49′N 14°26′ E. It is the only active volcano on the European mainland, although it is not currently erupting. ... May 14 is the 134th day of the year (135th in leap years) in the Gregorian calendar. ... June 4 is the 155th day of the year (156th in leap years) in the Gregorian calendar. ... Events 12 February — The San Carlo, the oldest working opera house in Europe, is inaugurated. ... A distant Rain Rain is a type of precipitation which forms when separate drops of water fall to the Earths surface from clouds. ...

10 m high fountain of lava
10 m high fountain of lava

Contents

Download high resolution version (3072x2048, 1374 KB)Image of a pahoehoe fountain. ... Download high resolution version (3072x2048, 1374 KB)Image of a pahoehoe fountain. ...

Lava composition

In general, a lava's composition determines its behavior more than the temperature of its eruption. Igneous rocks, which form lava flows when erupted, can be classified into three chemical types; felsic, intermediate, and mafic. These classes are primarily chemical; however, the chemistry of lava also tends to correlate with the magma temperature, its viscosity and its mode of eruption. Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium. ... In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ...


Felsic lavas such as rhyolite and dacite are often associated with strombolian eruptions, typically form lava domes and sheeted flows, and are associated with pyroclastic surge deposits and tuffs. Felsic lavas are extremely viscous. This is caused primarily by the chemistry of the magma, which is high in silica, aluminium, potassium, sodium, and calcium, forming a polymerized liquid rich in feldspar and quartz, which is thus much more sticky than other magma types. Felsic magmas can erupt at temperatures as low as 650 to 750 degrees Celsius, although they can be hotter. Felsic is a term used in geology to refer to silicate minerals, magmas, and rocks which are enriched in the lighter elements such as silica, oxygen, aluminium, sodium, and potassium. ... Rhyolite This page is about a volcanic rock. ... Gray, red, black, altered white/tan, flow-banded pumice dacite poop Dacite (IPA: ) is a high-silica igneous, volcanic rock. ... It has been suggested that this article or section be merged with Strombolian activity. ... One of the Mono Craters, an example of a rhyolite dome. ... Pyroclastic rocks are formed from lavas which are ejected into the air, as occur in pyroclastic flows or Plinian eruptions. ... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... The chemical compound silicon dioxide, also known as silica, is the oxide of silicon, chemical formula SiO2. ... General Name, Symbol, Number aluminium, Al, 13 Chemical series poor metals Group, Period, Block 13, 3, p Appearance silvery Standard atomic weight 26. ... General Name, Symbol, Number potassium, K, 19 Chemical series alkali metals Group, Period, Block 1, 4, s Appearance silvery white Standard atomic weight 39. ... General Name, Symbol, Number sodium, Na, 11 Chemical series alkali metals Group, Period, Block 1, 3, s Appearance silvery white Standard atomic weight 22. ... General Name, Symbol, Number calcium, Ca, 20 Chemical series alkaline earth metals Group, Period, Block 2, 4, s Appearance silvery white Standard atomic weight 40. ... A polymer is a substance composed of molecules with large molecular mass composed of repeating structural units, or monomers, connected by covalent chemical bonds. ... This article does not cite any references or sources. ... Quartz is one of the most common minerals in the Earths continental crust. ...


Intermediate or Andesitic lavas are lower in aluminium and silica, and usually somewhat richer in magnesium and iron. Intermediate lavas form andesite domes and sheeted flows, are usually associated with strombolian eruptions, and form composite volcanoes. Poorer in aluminium and silica than felsic lavas, and also hotter (in the range of 750 to 950 degrees Celsius), they tend to be less viscous. Greater temperatures tend to destroy polymerized bonds within the magma, promoting more fluid behaviour and also a greater tendency to form phenocrysts. Higher iron and magnesium tends to manifest as a darker groundmass, and also occasionally amphibole or pyroxene phenocrysts. General Name, Symbol, Number magnesium, Mg, 12 Chemical series alkaline earth metals Group, Period, Block 2, 3, s Appearance silvery white solid at room temp Standard atomic weight 24. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ... The matrix or groundmass of rock is the fine-grained mass of material in which larger grains or crystals are embedded. ... For the logical fallacy, see Amphibology. ... Figure 1:Mantle-peridotite xenolith with green peridot olivine and black pyroxene crystals from San Carlos Indian Reservation, Gila Co. ... Example of phenocrysts in rhomb porphyry from the Oslo rift area in Norway A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ...


Mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 degrees Celsius. Basaltic magma is high in iron and magnesium, and has relatively lower aluminium and silica, which taken together reduces the degree of polymerization within the melt. Due to the higher temperatures, viscosities can be relatively low, although still thousands of times more viscous than water. The low degree of polymerization and high temperature favors chemical diffusion, so it is common to see large, well-formed phenocrysts within mafic lavas. Basalt volcanoes tend to form shield volcanoes, as the fluid magma tends to form thin, widely distributed flows. In geology, mafic minerals and rocks are silicate minerals, magmas, and volcanic and intrusive igneous rocks that have relatively high concentrations of the heavier elements. ... Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ... Shield volcano A shield volcano is a large volcano with shallowly-sloping sides. ...


Ultramafic lavas such as komatiite and highly magnesian magmas which form boninite take the composition and temperatures of eruptions to the extreme. Komatiites contain over 18% magnesium oxide, and are thought to have erupted at temperatures of 1600 °C. At this temperature there is no polymerization of the mineral compounds, creating a highly mobile liquid with viscosity as low as that of water. Most if not all ultramafic lavas are no younger than the Proterozoic, with a few ultramafic magmas known from the Phanerozoic. No modern komatiite lavas are known, as the Earth's mantle has cooled too much to produce highly magnesian magmas. Igneous rock which crystallizes from silicate minerals at the highest temperatures is referred to as ultramafic rock. ... Komatiites are ultramafic mantle-derived volcanic rocks. ... Boninite is a high magnesium mafic extrusive rock formed in back-arc environments, typically in seafloor spreading centres but also in terrestrial back-arc spreading centres. ... The Proterozoic (IPA: ) is a geological eon representing a period before the first abundant complex life on Earth. ... The Phanerozoic (occasionally Phaenerozoic) Eon is the period of geologic time during which abundant animal life has existed. ...


Lava behavior

The viscosity of lava is important because it determines how the lava will behave. Lavas with high viscosity are rhyolite, dacite, andesite and trachyte, with cooled basaltic lava also quite viscous; those with low viscosities are freshly erupted basalt, carbonatite and the unusual sulphide lavas, and occasionally andesite. Rhyolite This page is about a volcanic rock. ... Gray, red, black, altered white/tan, flow-banded pumice dacite poop Dacite (IPA: ) is a high-silica igneous, volcanic rock. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... A sample of trachyte Trachyte is an igneous, volcanic rock with an aphanitic to porphyritic texture. ... Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ... Carbonatites are intrusive igneous rock structures with more than 50% carbonate content, many of which contain distinctive abundances of apatite, magnetite, barite, and fluorite, that may contain economic or anomalous concentrations of rare earth elements, phosphorus, niobium, uranium, thorium, copper, iron, titanium, barium, fluorine, zirconium, and other rare or incompatible... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ...


Highly viscous lava shows the following behaviors:

  • It tends to flow slowly, clog, and form semi-solid blocks which resist flow
  • It tends to entrap gasses, which form bubbles within the rock as they rise to the surface
  • It correlates with explosive or phreatic eruptions and is associated with tuff and pyroclastic flows

Highly viscous lavas do not usually flow as liquid, and usually form explosive fragmental ash and tephra deposits. However, a degassed viscous lava or one which erupts somewhat hotter than usual may form a lava flow. Viscous lavas have two forms of non-pyroclastic eruptions, lava domes and sheeted flows. The term phreatic is used in geology to refer to matters relating to underground water below the water table (the word originates from the Greek phrear, phreat- meaning well or spring). The phreatic zone is the layer(s) of soil or rock below the water table in which voids are... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ... Pyroclastic rocks are formed from lavas which are ejected into the air, as occur in pyroclastic flows or Plinian eruptions. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ...


Lava with low viscosity shows the following behaviors:

  • It tends to flow easily, forming puddles, channels, and rivers of molten rock
  • It tends to easily release bubbling gases as they are formed
  • Eruptions are rarely pyroclastic and are usually quiescent
  • Volcanoes tend to form as rifts, not steep cones

There are three forms of low-viscosity lava flows: ʻaʻā, pāhoehoe, and pillow lava. They are described in relation to basaltic flows from Hawaii, shown in the following sections.


Lavas also may contain many other components, sometimes including solid crystals of various minerals, fragments of exotic rocks known as xenoliths and parts of its own solidified lava products. A xenolith A xenolith (Greek: foreign rock) is a rock fragment which becomes enveloped in a larger rock during the latters development and hardening. ...


Volcanic Morphologies

The physical behaviour of lava creates the physical forms of a lava flow or volcano. More fluid basaltic lava flows tend to form flat sheets and lobes of lava, whereas viscous rhyolite forms knobbly, rubbly masses of rock.


General features of volcanology can be used to classify volcanic edifices and provide information on the eruptions which formed the lava flow, even if the sequence of lavas have been buried or metamorphosed. Volcanology (also spelled vulcanology) is the study of volcanoes, lava, magma, and related geological phenomena. ...


The ideal lava flow will have a brecciated top, either as pillow lava development, autobreccia and rubble typical of ʻaʻā and viscous flows, or a vesicular or frothy carapace such as scoria or pumice. The flow top will tend to be glassy, having been flash frozen in contact with the air or water. Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ... Scoria Scoria is the vesicular ejecta of mafic to intermediate magmas such as basalt and andesite. ... // Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ...


The centre of the lava flow will ideally be massive and crystalline, though usually the crystals will be microscopic. The more viscous lava forms tend to show sheeted flow features, and blocks or breccia entrained within the sticky lava. The crystal size at the centre of a lava will in general be greater than at the margins, as the crystals have more time to grow.


The flow base tends to show evidence of hydrothermal activity, generally because the lava is erupted onto moist or wet substrates. The flow base may have vesicles, perhaps filled with minerals (amygdules). The substrate upon which the lava has flowed may show signs of scouring, it may be broken or disturbed due to the boiling of trapped water, and in the case of soil profiles, may be baked into a brick-red clay. Amygdules form when the vesicular cavities (created by expanding gas bubbles in volcanic lava) are filled with a secondary mineral such as calcite, quartz, or one of the zeolites, which are deposited by having minerals wash through the pores in the rock (see Porosity/Permeability). ... The Gay Head cliffs in Marthas Vineyard are made almost entirely of clay. ...


Discriminating between a sill and a lava flow in ancient rock sequences can be difficult. However, sills do not usually have brecciated margins, they show greater propensity to form a chilled margin, and may show a weak metamorphic aureole on both the upper and lower surface whereas a lava flow will only metamorphose the lower surface. However, it is often difficult in practise to identify these metamorphic phenomenon because they are usually weak and restricted in size.


Lava domes

Shiprock, New Mexico, United States: a volcanic neck in the distance, with radiating dike on its south side. Photo credit: USGS Digital Data Series
Shiprock, New Mexico, United States: a volcanic neck in the distance, with radiating dike on its south side. Photo credit: USGS Digital Data Series

Cooling viscous lava often clogs a volcanic vent, allowing pressure behind the blockage to build; trapped gasses within the lava also add to the pressure, eventually producing cataclysmic explosions, ejecting great clouds of volcanic ash and gas, and producing pyroclastic flows. Most explosive eruptions tend to be followed by a quieter period of lava extrusion. Shiprock, New Mexico a volcanic neck in the distance, with radiating dike on its south side. ... Shiprock, New Mexico a volcanic neck in the distance, with radiating dike on its south side. ... Shiprock Shiprock, or Shiprock Peak (Dine: Tsé Bit Aí, winged rock) is a rock formation rising nearly 1,800 feet (540 meters) above the high-desert plain on the Navajo reservation, near the northern New Mexico town of Shiprock. ... InsertSLUTTY WHORES≤ non-formatted text here{| class=toccolours border=1 cellpadding=4 style=float: right; margin: 0 0 1em 1em; width: 20em; border-collapse: collapse; font-size: 95%; clear: right; |+ United States Geological Survey |- |style= align=center colspan=2| [[Image:USGS logo. ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Pyroclastic flows are a common and devastating result of some volcanic eruptions. ...


Sometimes as a volcano extrudes silicic lava, it forms an inflation dome, gradually building up a large, pillow-like structure which cracks, fissures, and may release cooled chunks of rock and rubble. The top and side margins of an inflating lava dome tend to be covered in fragments of rock, breccia and ash. Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ...


Examples of lava dome eruptions include the Novarupta dome, and successive lava domes of Mount St Helens. Novarupta, meaning new eruption, is a volcano located on the Alaska Peninsula in the Katmai area, about 290 miles southwest of Anchorage. ... Mount St. ...


Sheeted flows

Sheeted flows are an uncommon form of eruptive phenomena of felsic and intermediate volcanoes. Internal pressure of gases tend to promote pyroclastic and explosive eruptions. However, a viscous magma will flow, though very slowly, across the surface of the Earth.


Typically the lava flow forms a sheeted flow or laminar flow, with the upper and lower margins of the flowing lava forming a hard, brittle shell inside of which the sticky, viscous lava will be flowing. The hard skin forms a chaotic igneous breccia called autobreccia, as the flow creeps along, churning the outer margins apart. This is similar to an ʻaʻā flow except that the inner lava will show evidence of stretching, plastic deformation and even foliation of the highly viscous lava. Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ... Foliation is any penetrative planar fabric present in rocks. ...


Examples of laminar or sheeted flows include the Tertiary aged volcanic edifices of the Glasshouse mountains, and the cliffs of Kangaroo Point in Brisbane, Australia. For other uses, see Tertiary (disambiguation). ... Coonowrin, one of the more notable of the Glasshouse Mountains Glasshouse Mountains is a national park in Queensland (Australia), 70 km north of Brisbane. ... Kangaroo Point is a suburb of Sydney, in the state of New South Wales, Australia. ...


ʻAʻā

Glowing ʻaʻā flow front advancing over pāhoehoe on the coastal plain of Kīlauea in Hawaiʻi, United States.

ʻAʻā (also spelled aa, aʻa, ʻaʻa and a-aa, IPA: /ˈʔɑʔɑː/, Hawaiian English, from Hawaiian meaning "stony with rough lava", but also to "burn" or "blaze") is one of three basic types of flow lava. ʻAʻā is basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinker. [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... [1] File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... KÄ«lauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... Official language(s) English, Hawaiian Capital Honolulu Largest city Honolulu Area  Ranked 43rd  - Total 10,931 sq mi (29,311 km²)  - Width n/a miles (n/a km)  - Length 1,522 miles (2,450 km)  - % water 41. ... Articles with similar titles include the NATO phonetic alphabet, which has also informally been called the “International Phonetic Alphabet”. For information on how to read IPA transcriptions of English words, see IPA chart for English. ... Hawaiian English is the standard of the English language as used in the State of Hawaii, and is—along with the Hawaiian language—an official language of the state. ... The Hawaiian language is an Austronesian language that takes its name from that of the largest island in the tropical North Pacific archipelago where it developed. ... Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ... Clinker has several meanings: In boat building, clinker is a method of constructing wooden boats by fixing planks to a frame so that the planks overlap each other gaining support from the frame and from adjacent planks. ...


The loose, broken, and sharp, spiny surface of an ʻaʻā flow makes walking difficult and slow. The clinkery surface actually covers a massive dense core, which is the most active part of the flow. As pasty lava in the core travels downslope, the clinkers are carried along at the surface. At the leading edge of an ʻaʻā flow, however, these cooled fragments tumble down the steep front and are buried by the advancing flow. This produces a layer of lava fragments both at the bottom and top of an ʻaʻā flow.


Accretionary lava balls as large as 3 m (10 ft) are common on ʻaʻā flows. ʻAʻā is usually of higher viscosity than pāhoehoe (often spelled just pahoehoe). Pāhoehoe can turn into ʻaʻā if it becomes turbulent due to meeting impediments or steep slopes.


The sharp, angled texture makes ʻaʻā a strong radar reflector, and can easily be seen from an orbiting satellite (bright on Magellan pictures). Magellan spacecraft at Kennedy Space Center The Magellan spacecraft carried out a mission from 1989-1994, orbiting Venus from 1990-1994. ...


ʻAʻā lavas typically erupt at temperatures of 1000 to 1100 °C.


Pāhoehoe

Toes of a pāhoehoe advance across a road in Kalapana on the east rift zone of Kīlauea Volcano in Hawaiʻi, United States.
Toes of a pāhoehoe advance across a road in Kalapana on the east rift zone of Kīlauea Volcano in Hawaiʻi, United States.

Pāhoehoe (also spelled pahoehoe, IPA: /pəˈhəʊɪhəʊi/, Hawaiian English, from Hawaiian, meaning "smooth, unbroken lava") is basaltic lava that has a smooth, billowy, undulating, or ropy surface. These surface features are due to the movement of very fluid lava under a congealing surface crust. Image File history File links Download high resolution version (500x800, 85 KB) Pahoehoe - Hawaiian smooth lava. ... Image File history File links Download high resolution version (500x800, 85 KB) Pahoehoe - Hawaiian smooth lava. ... One of the over 100 houses destroyed by the lava flow in 1990 Kalapana is a town on the Island of Hawai‘i in the Hawaiian Islands that was completely destroyed and partly buried by the eruptive flow of lava from Kīlauea volcano in 1990. ... KÄ«lauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... Official language(s) English, Hawaiian Capital Honolulu Largest city Honolulu Area  Ranked 43rd  - Total 10,931 sq mi (29,311 km²)  - Width n/a miles (n/a km)  - Length 1,522 miles (2,450 km)  - % water 41. ... Articles with similar titles include the NATO phonetic alphabet, which has also informally been called the “International Phonetic Alphabet”. For information on how to read IPA transcriptions of English words, see IPA chart for English. ... Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ...

Pāhoehoe lava from Kīlauea flowing through a tube system down Pulama Pali, Hawaii, United States.

A pāhoehoe flow typically advances as a series of small lobes and toes that continually break out from a cooled crust. Also forms lava tubes where the minimal heat loss maintains low viscosity. The surface texture of pāhoehoe flows varies widely, displaying all kinds of bizarre shapes often referred to as lava sculpture. With increasing distance from the source, pāhoehoe flows may change into ʻaʻā flows in response to heat loss and consequent increase in viscosity. Pahoehoe lavas typically have a temperature of 1100 to 1200 °C. Image File history File linksMetadata Download high resolution version (3264x2448, 5869 KB) Summary http://www. ... Image File history File linksMetadata Download high resolution version (3264x2448, 5869 KB) Summary http://www. ... Thurston Lava Tube in Hawaii Volcanoes National Park. ...

Pāhoehoe Lava is entering Pacific at The Big Island of Hawaii, Hawaii Volcanoes National Park in April of 2005
Pāhoehoe Lava is entering Pacific at The Big Island of Hawaii, Hawaii Volcanoes National Park in April of 2005

The rounded texture makes pāhoehoe a poor radar reflector, and is difficult to see from an orbiting satellite (dark on Magellan pictures). Image File history File links Size of this preview: 731 × 599 pixelsFull resolution (2148 × 1761 pixel, file size: 1. ... Image File history File links Size of this preview: 731 × 599 pixelsFull resolution (2148 × 1761 pixel, file size: 1. ... The Island of HawaiÊ»i (called the Big Island or HawaiÊ»i proper) is one of eight main islands that make up the U.S. state of HawaiÊ»i. ... HawaiÊ»i Volcanoes National Park, established in 1916, displays the results of hundreds of thousands of years of volcanism, migration, and evolution—processes that thrust a bare land from the sea and clothed it with complex and unique ecosystems and a distinct human culture. ...


Pillow lava

Pillow lava (NOAA)
Pillow lava (NOAA)

Pillow lava is the rock type typically formed when lava emerges from an underwater volcanic vent or a lava flow enters the ocean. The viscous lava gains a solid crust immediately upon contact with the water, and this crust cracks and oozes additional large blobs or "pillows" as more lava emerges from the advancing flow. Since the majority of Earth's surface is covered by water, and most volcanoes are situated near or under it, pillow lava is very common. Examples of this can be seen at Llanddwyn Island. Image ID: nur05018, National Undersearch Research Program (NURP) Collection Location: Hawaii Photo Date: 1988 July Credit: OAR/National Undersea Research Program (NURP) This NOAA image was previously uploaded as Image:Pillow lava small. ... Image ID: nur05018, National Undersearch Research Program (NURP) Collection Location: Hawaii Photo Date: 1988 July Credit: OAR/National Undersea Research Program (NURP) This NOAA image was previously uploaded as Image:Pillow lava small. ... Submarine volcanoes and volcanic vents are common features on certain zones of the ocean floor. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Ynys Llanddwyn or Llanddwyn Island is a small tidal island off the west coast of Anglesey, north Wales. ...


Lava landforms

Due to being formed from viscous molten rock, lava flows and eruptions create distinctive formations, landforms and topographical features from the macroscopic to the microscopic.


Volcanoes

Main article: Volcano
Mount Fuji, Japan, is a composite volcanic cone formed from basaltic andesite.
Mount Fuji, Japan, is a composite volcanic cone formed from basaltic andesite.

Volcanoes are the primary landform created by lava eruption and consist of flattish, shallow shield volcanes formed from basalt to steeply-sided ash and lava composite volcanic cones typical of andesite and rhyolite lavas. For other uses, see Volcano (disambiguation). ... Image File history File links Download high resolution version (1024x768, 169 KB) This photograph shows Mt. ... Image File history File links Download high resolution version (1024x768, 169 KB) This photograph shows Mt. ... Mount Fuji Mount Fuji , IPA: )   is the highest mountain in Japan. ...


Volcanoes can form calderas if they are obliterated by large pyroclastic or phreatic eruptions, and such features typically include volcanic crater lakes and lava domes after the event. Satellite image of Santorini. ... The term phreatic is used in geology to refer to matters relating to underground water below the water table (the word originates from the Greek phrear, phreat- meaning well or spring). The phreatic zone is the layer(s) of soil or rock below the water table in which voids are...


Cinder and spatter cones

Main article: Volcanic cone

Cinder cones and spatter cones are small-scale features formed by lava accumulation around a small vent on a volcanic edifice. Cinder cones are formed from tephra or ash and tuff which is thrown from an explosive vent. Spatter cones are formed by accumulation of molten volcanic slag and cinders ejected in a more liquid form. Puʻu ʻŌʻō, a cinder-and-spatter cone on Kīlauea, Hawaiʻi Volcanic cones are among the simplest volcano formations in the world. ... Cinder Cone is a cinder cone volcano in Lassen Volcanic National Park. ... Tephra refers to air-fall material produced by a volcanic eruption regardless of composition or fragment size. ... Ash plume from Mt Cleveland, a stratovolcano Diamond Head, a well-known backdrop to Waikiki in Hawaii, is an ash cone that solidified into tuff Volcanic ash consists of very fine rock and mineral particles less than 2 mm in diameter that are ejected from a volcanic vent. ... Welded tuff at Golden Gate in Yellowstone National Park Tuff (from the Italian tufo) is a type of rock consisting of consolidated volcanic ash ejected from vents during a volcanic eruption. ...


Kīpukas

Main article: Kīpuka

Another Hawaiian English term derived from the Hawaiian language, a kīpuka denotes an elevated area such as a hill, ridge or old lava dome inside or downslope from an area of active volcanism. New lava flows will cover the surrounding land, isolating the kīpuka so that it appears as a (usually) forested island in a barren lava flow. Lava flows and kÄ«pukas at Holei Pali in Hawaii Volcanoes National Park. ... Hawaiian English is the standard of the English language as used in the State of Hawaii, and is—along with the Hawaiian language—an official language of the state. ... The Hawaiian language is an Austronesian language that takes its name from that of the largest island in the tropical North Pacific archipelago where it developed. ...


Lava domes

Main article: Lava dome
A forested lava dome in the midst of the Valle Grande, the largest meadow in the Valles Caldera National Preserve, New Mexico, United States.
A forested lava dome in the midst of the Valle Grande, the largest meadow in the Valles Caldera National Preserve, New Mexico, United States.

Lava domes are formed by the extrusion of viscous felsic magma. They can form prominent rounded protuberances, such as at Valle Calderas. One of the Mono Craters, an example of a rhyolite dome. ... Image File history File linksMetadata Download high resolution version (2841x1390, 1282 KB)A forested lava dome in the midst of the Valle Grande, the largest meadow in the Valles Caldera National Preserve. ... Image File history File linksMetadata Download high resolution version (2841x1390, 1282 KB)A forested lava dome in the midst of the Valle Grande, the largest meadow in the Valles Caldera National Preserve. ... Valle Grande (Va-lye Gra-n-de), known to geologists as the Valles Caldera and the Jemez Caldera, is a pristine area in the Jemez Mountains of northern New Mexico in the United States. ...


Lava tubes

Main article: Lava tube

Lava tubes are formed when a flow of relatively fluid lava cools on the upper surface sufficiently to form a crust. Beneath this crust, which by dint of being made of rock is an excellent insulator, the lava can continue to flow as a liquid. When this flow occurs over a prolonged period of time the lava conduit can form a tunnel-like aperture or lava tube, which can conduct molten rock many kilometres from the vent without cooling appreciably. Often these lava tubes drain out once the supply of fresh lava has stopped, leaving a considerable length of open tunnel within the lava flow. Thurston Lava Tube in Hawaii Volcanoes National Park. ...


Lava tubes are known from the modern day eruptions of Kīlauea, and significant, extensive and open lava tubes of Tertiary age are known from North Queensland, Australia, some extending for 15 kilometres. Capital Brisbane Government Constitutional monarchy Governor Quentin Bryce Premier Peter Beattie (ALP) Federal representation  - House seats 28  - Senate seats 12 Gross State Product (2004-05)  - Product ($m)  $158,506 (3rd)  - Product per capita  $40,170/person (6th) Population (End of November 2006)  - Population  4,164,590 (3rd)  - Density  2. ...


Lava cascades and fountains

A lava cascade in Hawaiʻi, United States

The eruptions of lava are sometimes attended by peculiarities which impart to them much additional grandeur. Instances have occurred in which the fiery stream has plunged over a sheer precipice of immense height, so as to produce a glowing cascade exceeding (in breadth and perpendicular descent) the celebrated Niagara Falls. In other cases, the lava, instead of at once flowing down the sides of the mountain, has been first thrown up into the air as a fiery fountain several hundred feet in height (see Volcanic cone). Image File history File links Lavafall. ... Image File history File links Lavafall. ... For other uses, see Niagara Falls (disambiguation). ... Puʻu ʻŌʻō, a cinder-and-spatter cone on Kīlauea, Hawaiʻi Volcanic cones are among the simplest volcano formations in the world. ...


Lava lakes

Main article: Lava lake

Rarely, a volcanic cone may fill with lava but not erupt. Lava which pools within the caldera is known as a lava lake. Lava lakes do not usually persist for long, either draining back into the magma chamber once pressure is relieved (usually by venting of gases through the caldera), or by draining via eruption of lava flows or pyroclastic explosion. A lava lake in Hawaii Lava lakes are large volumes of molten lava, usually basaltic, contained in a vent, volcanic crater, or broad depression. ...


There are only a few sites in the world where permanent lakes of lava exist. These include:

Mount Erebus in Antarctica is the southernmost active volcano on Earth. ... Puu Ōō (which means Hill of the Ōō Bird in Hawaiian, is often written as Puu Oo, and is roughly pronounced Poo-oo Ohh-ohh or in the IPA) is a cinder/spatter cone in the eastern rift zone of the KÄ«lauea volcano of the Hawaiian Islands. ... KÄ«lauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... Official language(s) English, Hawaiian Capital Honolulu Largest city Honolulu Area  Ranked 43rd  - Total 10,931 sq mi (29,311 km²)  - Width n/a miles (n/a km)  - Length 1,522 miles (2,450 km)  - % water 41. ... Erta Ale is an active shield volcano in Ethiopia, known for its long-standing lava lake activity. ... Mount Nyiragongo is a dormant volcano in the Virunga Mountains associated with the Great Rift Valley or East African Rift. ...

Composition of volcanic rocks

ʻAʻā next to pāhoehoe lava at the Craters of the Moon National Monument and Preserve, Idaho, United States.
ʻAʻā next to pāhoehoe lava at the Craters of the Moon National Monument and Preserve, Idaho, United States.

The sub-family of rocks which form from volcanic lava are called igneous volcanic rocks (to differentiate them from igneous rocks which form from magma, below the surface of the earth, called igneous plutonic rocks). Photo taken by Daniel Mayer and released under terms of the GNU FDL. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Photo taken by Daniel Mayer and released under terms of the GNU FDL. File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Craters of the Moon National Monument and Preserve is a national monument and national preserve located in the Snake River Plain in central Idaho near Arco, Idaho. ... Ignimbrite is a deposit of a pyroclastic flow. ... Devils Tower, an igneous intrusion exposed when the surrounding softer rock eroded away. ...


The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition. If a rhyolite lava-stream cools quickly, it can quickly freeze into a black glassy substance called obsidian. When filled with bubbles of gas, the same lava may form the spongy mineral pumice. Allowed to cool slowly, it forms a light-colored, uniformly solid rock called rhyolite. Rhyolite This page is about a volcanic rock. ... Obsidian from Lake County, Oregon Counterclockwise from top: obsidian, pumice and rhyolite (light color) Obsidian is a rock which is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth (see glass transition temperature). ... // Specimen of highly porous pumice from Teide volcano on Tenerife, Canary Islands. ... Rhyolite This page is about a volcanic rock. ...


The lavas, having cooled rapidly in contact with the air or water, are mostly finely crystalline or have at least fine-grained ground-mass representing that part of the viscous semi-crystalline lava flow which was still liquid at the moment of eruption. At this time they were exposed only to atmospheric pressure, and the steam and other gases, which they contained in great quantity were free to escape; many important modifications arise from this, the most striking being the frequent presence of numerous steam cavities (vesicular structure) often drawn out to elongated shapes subsequently filled up with minerals by infiltration (amygdaloidal structure). As crystallization was going on while the mass was still creeping forward under the surface of the Earth, the latest formed minerals (in the ground-mass) are commonly arranged in subparallel winding lines following the direction of movement (fluxion or fluidal structure), and the larger early minerals which had previously crystallized may show the same arrangement. Most lavas have fallen considerably below their original temperatures before they are emitted. In their behavior they present a close analogy to hot solutions of salts in water, which, when they approach the saturation temperature, first deposit a crop of large, well-formed crystals (labile stage) and subsequently precipitate clouds of smaller less perfect crystalline particles (metastable stage). In igneous rocks the first generation of crystals generally forms before the lava has emerged to the surface, that is to say, during the ascent from the subterranean depths to the crater of the volcano. It has frequently been verified by observation that freshly emitted lavas contain large crystals borne along in a molten, liquid mass. The large, well-formed, early crystals (phenocrysts) are said to be porphyritic; the smaller crystals of the surrounding matrix or ground-mass belong to the post-effusion stage. More rarely lavas are completely fused at the moment of ejection; they may then cool to form a non-porphyritic, finely crystalline rock, or if more rapidly chilled may in large part be non-crystalline or glassy (vitreous rocks such as obsidian, tachylyte, pitchstone). A common feature of glassy rocks is the presence of rounded bodies (spherulites), consisting of fine divergent fibres radiating from a center; they consist of imperfect crystals of feldspar, mixed with quartz or tridymite; similar bodies are often produced artificially in glasses which are allowed to cool slowly. Rarely these spherulites are hollow or consist of concentric shells with spaces between (lithophysae). Perlitic structure, also common in glasses, consists of the presence of concentric rounded cracks owing to contraction on cooling. Vesicular texture is a volcanic rock texture characterised by, or containing, many vesicles. ... Amygdules form when the vesicular cavities (created by expanding gas bubbles in volcanic lava) are filled with a secondary mineral such as calcite, quartz, or one of the zeolites, which are deposited by having minerals wash through the pores in the rock (see Porosity/Permeability). ... The matrix or groundmass of an igneous rock consists of fine grained often microscopic crystals in which larger crystals (phenocrysts) are embedded. ... Example of phenocrysts in rhomb porphyry from the Oslo rift area in Norway A phenocryst is a relatively large and usually conspicuous crystal formed in the mass of a porphyritic igneous rock. ... (For other meanings of Porphyr, see Porphyry) The baptismal font in the Cathedral of Magdeburg is made of rose porphyry from a site near Assuan, Egypt Porphyry is a very hard red, green or purple igneous rock consisting of large-grained crystals, such as feldspar or quartz, dispersed in a... Obsidian from Lake County, Oregon Counterclockwise from top: obsidian, pumice and rhyolite (light color) Obsidian is a rock which is a type of naturally occurring glass, produced by volcanoes (igneous origin) when a felsic lava cools rapidly and freezes without sufficient time for crystal growth (see glass transition temperature). ... Tachylyte is a vitreous form of basaltic obsidian (volcanic glass). ... Pitchstone ridge An Sgurr, Isle of Eigg, Scotland Pitchstone is a dull black glassy volcanic rock formed when lava cools swiftly. ... Spherulites, in petrology, are small, rounded bodies that commonly occur in vitreous igneous rocks. ... Tridymite Tridymite is a high-temperature polymorph of quartz and usually occurs as minute tabular white or colorless pseudo-hexagonal triclinic crystals, or scales, in cavities in acidic volcanic rocks. ... A lithophysa (plural lithophysae) is a small cavity found in felsic volcanic rocks believed to be caused by expanding gases in tuffs before solidification. ... Expanded Perlite Perlite is an amorphous volcanic glass that has a relatively high water content. ...


The phenocrysts or porphyritic minerals are not only larger than those of the ground-mass; as the matrix was still liquid when they formed they were free to take perfect crystalline shapes, without interference by the pressure of adjacent crystals. They seem to have grown rapidly, as they are often filled with enclosures of glassy or finely crystalline material like that of the ground-mass . Microscopic examination of the phenocrysts often reveals that they have had a complex history. Very frequently they show layers of different composition, indicated by variations in color or other optical properties; thus augite may be green in the center surrounded by various shades of brown; or they may be pale green centrally and darker green with strong pleochoism (aegirine) at the periphery. In the feldspars the center is usually richer in calcium than the surrounding layers, and successive zones may often be noted, each less calsic than those which lie within it. Phenocrysts of quartz (and of other minerals), instead of sharp, perfect crystalline faces, may show rounded corroded surfaces, with the points blunted and irregular tongue-like projections of the matrix into the substance of the crystal. It is clear that after the mineral had crystallized it was partly again dissolved or corroded at some period before the matrix solidified. Corroded phenocrysts of biotite and hornblende are very common in some lavas; they are surrounded by black rims of magnetite mixed with pale green augite. The hornblende or biotite substance has proved unstable at a certain stage of consolidation and has been replaced by a paramorph of augite and magnetite which may be partially or completely substituted for the original crystal but still retains its characteristic outlines.[1] Aegirine is an inosilicate member of the clinopyroxene group. ...


Unusual lavas

Four types of unusual volcanic rocks have been recognised as erupting onto the surface of the Earth;

Carbonatites are intrusive igneous rock structures with more than 50% carbonate content, many of which contain distinctive abundances of apatite, magnetite, barite, and fluorite, that may contain economic or anomalous concentrations of rare earth elements, phosphorus, niobium, uranium, thorium, copper, iron, titanium, barium, fluorine, zirconium, and other rare or incompatible... Natrocarbonatite is made up largely of two minerals, nyerereite (named after Julius Nyerere, the first president of independent Tanzania) and gregoryite (named after John Walter Gregory, one of the first geologists to study the Great Rift Valley and author of the book The Great Rift Valley). ... Ol Doinyo Lengai is a volcano located in Tanzania and is part of the volcanic system of the Great Rift Valley in eastern Africa. ... Formally, sulfide is the dianion, S2−, which exists in strongly alkaline aqueous solutions formed from H2S or alkali metal salts such as Li2S, Na2S, and K2S. Sulfide is exceptionally basic and, with a pKa > 14, it does not exist in appreciable concentrations even in highly alkaline water. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Standard atomic weight 55. ... This heap of iron ore pellets will be used in steel production. ... Kiruna View from just outside Kiruna, with European route E10 left to LuleÃ¥ and right to Narvik, Norway. ... The Proterozoic (IPA: ) is a geological eon representing a period before the first abundant complex life on Earth. ... Columnar jointing in melilite-olivine nephelinite from the Southern Balcones volcanic and intrusive rocks, Uvalde County, Texas. ... Earth cutaway from core to exosphere. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ...

Hazards

Lava flows are enormously destructive to property in their path but generally move slowly enough for people to get out of their way, so casualties caused directly by active lava flows are rare. Nevertheless injuries and deaths have occurred, either because people had their escape route cut off, because they get too close to the flow [5]or, more rarely, if the lava flow front travels too quickly.


This notably happened during the eruption of Nyiragongo in Zaire (now Democratic Republic of Congo) on 10 January 1977 when the crater wall was breached during the night and the fluid lava lake in it drained out in less than an hour. Flowing down the steep slopes of the volcano at up to 60 miles per hour (100 km per hour), the lava swiftly overwhelmed several villages whilst their residents were asleep. As a result of this disaster, the mountain was designated a Decade Volcano in 1991[6]. Mount Nyiragongo is a dormant volcano in the Virunga Mountains associated with the Great Rift Valley or East African Rift. ... January 10 is the 10th day of the year in the Gregorian calendar. ... Also: 1977 (album) by Ash. ... A map showing locations of the 16 Decade Volcanoes The Decade Volcanoes are 16 volcanoes identified by the International Association of Volcanology and Chemistry of the Earths Interior (IAVCEI) as being worthy of particular study in light of their history of large, destructive eruptions and proximity to populated areas. ...


Deaths attributed to volcanoes frequently have a different cause, for example volcanic ejecta, pyroclastic flow from a collapsing lava dome, lahars, or explosions caused when the flow comes into contact with water[5]. Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 Pyroclastic flows are a common and devastating result of some volcanic eruptions. ... Lahar from a March 1982 eruption of Mount St. ...


Towns destroyed by lava flows

Lava can easily destroy entire towns. This picture shows one of over 100 houses destroyed by the lava flow in Kalapana, Hawaiʻi, United States, in 1990.
Lava can easily destroy entire towns. This picture shows one of over 100 houses destroyed by the lava flow in Kalapana, Hawaiʻi, United States, in 1990.

United States Geological Survey photo of a house in Kalapana, Hawaii being destroyed by a pahoehoe flow. ... United States Geological Survey photo of a house in Kalapana, Hawaii being destroyed by a pahoehoe flow. ... One of the over 100 houses destroyed by the lava flow in 1990 Kalapana is a town on the Island of Hawai‘i in the Hawaiian Islands that was completely destroyed and partly buried by the eruptive flow of lava from Kīlauea volcano in 1990. ... Kaimū was a small town on the Island of Hawaii in the Hawaiian Islands that was completley destroyed by an eruptive flow of lava from the Puu Oo vent of the Kīlauea volcano in 1990. ... One of the over 100 houses destroyed by the lava flow in 1990 Kalapana is a town on the Island of Hawai‘i in the Hawaiian Islands that was completely destroyed and partly buried by the eruptive flow of lava from Kīlauea volcano in 1990. ... Kapoho, HawaiÊ»i was a town in Puna district, HawaiÊ»i County, HawaiÊ»i, located near the eastern tip of the island of HawaiÊ»i, in the easternmost end of the graben overlying KÄ«lauea rift zone. ... San Sebastiano al Vesuvio is a small village located on the western slopes of Mount Vesuvius. ...

Towns partially destroyed by lava flows

A computer-generated depiction of the eruption of Vesuvius in AD 79 which buried Pompeii, from the BBCs Pompeii: The Last Day. ... This article is about the mountain in Italy. ... Catania is the second largest city of Sicily with 306,464 inhabitants, has the second highest population density on the island and is the capital of the province which bears its name. ... Mount Etna (also known as Mongibeddu in Sicilian and Mongibello in Italian, a combination of Latin mont- and Arabic jebel, both meaning mountain) is an active volcano on the east coast of Sicily, close to Messina and Catania. ... Goma is a large city in the eastern Democratic Republic of the Congo. ... Mount Nyiragongo is a dormant volcano in the Virunga Mountains associated with the Great Rift Valley or East African Rift. ... Heimaey off of southwest Iceland Heimaey (pronounced HAY-mah-ay or IPA: ) is the largest island (13. ... Lava fountains tower over Heimaey in the early stages of the Eldfell eruption Eldfell is a cinder cone volcano just over 200 metres (650 feet) high on the Icelandic island of Heimaey. ... Kīlauea is an active volcano in the Hawaiian Islands, one of five shield volcanoes that together form the Island of Hawaii. ... Parícutin (or Volcán de Parícutin, commonly also accented Paricutín) is a volcano in the Mexican state of Michoacán, close to a lava-covered village of the same name. ... Nuevo San Juan Parangaricutiro, Michoacán, Mexico is a small village near the Paricutín volcano. ... Parícutin (or Volcán de Parícutin, commonly also accented Paricutín) is a volcano in the Mexican state of Michoacán, close to a lava-covered village of the same name. ...

References

  1. ^ This article incorporates text from the Encyclopædia Britannica Eleventh Edition article "Petrology", a publication now in the public domain.
  2. ^ http://www.geology.sdsu.edu/how_volcanoes_work/Unusual%20lava.html Vic Camp, How volcanoes work, Unusual Lava Types, San Diego State University, Geology
  3. ^ Guilbert, John M. and Charles F. Park, Jr.; 1986, The Geology of Ore Deposits, W. H. Freeman, pp556-557, ISBN 0-7167-1456-6
  4. ^ Guilbert, John M. and Charles F. Park, Jr.; 1986, The Geology of Ore Deposits, W. H. Freeman, pp404-405, ISBN 0-7167-1456-6
  5. ^ a b Lava Flows and Their Effects USGS
  6. ^ Nyiragongo -- Could it happen here? USGS Hawaiian Volcano Observatory

Encyclopædia Britannica, the 11th edition The Encyclopædia Britannica Eleventh Edition (1910–1911) is perhaps the most famous edition of the Encyclopædia Britannica. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...

External links

Wikimedia Commons has media related to:
lava
  • USGS definition of ʻAʻā
  • USGS definition of Pāhoehoe
  • Volcanic landforms of Hawaiʻi
  • USGS hazards associated with lava flows
  • Hawaiian Volcano Observatory Volcano Watch newsletter article on Nyiragongo eruptions, 31 January 2002
  • Google Maps Plot of World Volcanoes

 
 

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