The physical behavior of lava creates the physical forms of a lava flow or volcano.
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.
No modern komatiite lavas are known, as the Earth's mantle has cooled too much to produce highly magnesian magmas.
A notable example of loss of life by rapid lava flow is the eruption of Nyiragongo in Zaire (now Democratic Republic of Congo) on January 10, 1977.
The more viscous lava forms tend to show sheeted flow features, and blocks or breccia entrained within the sticky lava.
The crater wall was breached during the night and the fluid lava lake in it drained out in less than an hour.
Lava domes are formed by the extrusion of viscous felsic magma.
Lava is molten rock expelled by a volcano during an eruption.
Most explosive eruptions tend to be followed by a quieter period of lava extrusion.
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.
Highly viscous lavas do not usually flow as liquid, and usually form explosive fragmental ash and tephra deposits.
The rock formed from solidified lava (or magma) is called igneous rock.
Intermediate or andesitic lavas are lower in aluminum and silica, and usually somewhat richer in magnesium and iron.
The lavas of different volcanoes, when cooled and hardened, differ much in their appearance and composition.
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.
Beneath this crust, which by dint of being made of rock is an excellent insulator, the lava can continue to flow as a liquid.
Accretionary lava balls as large as 3 m (10 ft) are common on ?a?? flows.
The viscosity of lava is important because it determines how the lava will behave.
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.
The center of the lava flow will ideally be massive and crystalline, though usually the crystals will be microscopic.
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.
Poorer in aluminum and silica than felsic lavas, and also hotter (in the range of 750 to 950 °C), they tend to be less viscous.
Initially, a lava flow is inhospitable to life.
Lava tubes are formed when a flow of relatively fluid lava cools on the upper surface sufficiently to form a crust.
Lava tubes are known from the modern day eruptions of K?lauea, and significant, extensive and open lava tubes of Tertiary age are known from North Queensland, Australia, some extending for 15 kilometers.
The flow base tends to show evidence of hydrothermal activity, generally because the lava is erupted onto moist or wet substrates.
Lava flows are enormously destructive to property in their path, but they generally move slowly enough for people to get out of their way.
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.
The ideal lava flow will have a brecciated top, either as pillow lava development, autobreccia and rubble typical of ?a?? and viscous flows, or a vesicular or frothy carapace such as scoria or pumice.
More fluid basaltic lava flows tend to form flat sheets and lobes of lava, whereas viscous rhyolite forms knobbly, rubbly masses of rock.
Viscous lavas have two forms of non-pyroclastic eruptions, lava domes and sheeted flows.
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.
Active lava flows result in enormous loss of property, but they are usually slow enough for people to escape out of harm's way.
Most if not all ultramafic lavas are no younger than the Proterozoic, with a few ultramafic magmas known from the Phanerozoic.
Volcanoes are the primary landform created by lava eruption and consist of flattish, shallow shield volcanoes formed from basalt to steeply-sided ash and lava composite volcanic cones typical of andesite and rhyolite lavas.
Consequently, casualties caused directly by active lava flows are rare.
Lava that forms a pool within the caldera is known as a lava lake.
Ultramafic lavas such as komatiite and highly magnesian magmas which form boninite take the composition and temperatures of eruptions to the extreme.
Most lavas have fallen considerably below their original temperatures before they are emitted.
?A?? is basaltic lava characterized by a rough or rubbly surface composed of broken lava blocks called clinker.
Pillow lava is the rock type typically formed when lava emerges from an underwater volcanic vent or a lava flow enters the ocean.
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.
The eruptions of lava are sometimes attended by peculiarities that add to their grandeur.
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.
Lavas may also 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.
Intermediate lavas form andesite domes and sheeted flows, are usually associated with strombolian eruptions, and form composite volcanoes.
The subfamily of rocks formed from volcanic lava are called igneous volcanic rocks.
Igneous rocks, formed from solidified lava, can be classified into three chemical types: felsic, intermediate, and mafic.
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.
Cinder cones and spatter cones are small-scale features formed by lava accumulation around a small vent on a volcanic edifice.
When filled with bubbles of gas, the same lava may form the spongy mineral pumice.
The hardened formation is called "lava flow," whereas the material that still contains molten rock is called an "active lava flow."
On rare occasions, the lava has moved too quickly.
Mafic or basaltic lavas are typified by their high ferromagnesian content, and generally erupt at temperatures in excess of 950 °C.
When first exuded from a volcanic vent, the hot lava is at temperatures ranging from 700 °C to 1,200 °C (1,300 °F to 2,200 °F).
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 kilometers from the vent without cooling appreciably.
Rarely, a volcanic cone may fill with lava but not erupt.
?A?? (also spelled aa, a?a, ?a?a and aa-aa, IPA: /???????/, Hawaiian English, from Hawaiian meaning "stony with rough lava," but also to "burn" or "blaze") is one of three basic types of flow lava.
The top and side margins of an inflating lava dome tend to be covered in fragments of rock, breccia and ash.
The word lava comes from Italian, and is probably derived from the Latin word labes which means a fall, slide, or sinking in.
On the positive side, the scientific study of lavas helps us understand the structure, composition, and evolution of the Earth's crust and mantle.
The low degree of polymerization and high temperature favors chemical diffusion, so it is common to see large, well-formed phenocrysts within mafic lavas.
Nevertheless, injuries and deaths have occurred when people had their escape routes cut off, or if they were too close to the flow, or (more rarely) if the lava flow front traveled too quickly.
Discriminating between a sill and a lava flow in ancient rock sequences can be difficult.
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.
P?hoehoe (also spelled pahoehoe, IPA: /p??h???h??i/, Hawaiian English, from Hawaiian, meaning "smooth, unbroken lava") is basaltic lava that has a smooth, billowy, undulating, or ropy surface.
Earth's inner mantle consists of hot, flowing rock that circulates extremely slowly, and is often explained by analogy to the flow in a lava lamp. But Jánosi found that there are some key differences. The wax in a lava lamp is more viscous than water, meaning it flows less easily.Sep 29, 2009