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Geology glossary

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lava bench

Volcanology
A lava bench in formation: active lava flows covering a small beach, forming a solid cap.
A lava bench in formation: active lava flows covering a small beach, forming a solid cap.
A lava bench is a platform formed by new lava flows that extends the old shoreline; in particular, this can be observed on Hawaii at Kilauea volcano during times when lava is entering the ocean, forming new land.
In their young stadium, benches are highly unstable. They often are underlain only by loose material such as sand and wave-eroded rock. Young benches can collapse at any time, and it is life-threatening to stand on one. Only after a long time, when the pile of material under and in front of the bench is sufficiently stabilized, the bench can be considered new stable land. -> See whole entry

lava flow

Volcanology
Lava flows near the coast from Kilauea volcano, Hawai'i
Lava flows near the coast from Kilauea volcano, Hawai'i
Lava flow on Stromboli volcano flowing down the Sciara del Fuoco and entering the sea
Lava flow on Stromboli volcano flowing down the Sciara del Fuoco and entering the sea
Lava flows are almost self-explanatory. When magma is erupted in molten or a partially molten state it often has the ability to flow. This is typically the case for basaltic volcanoes such as Hawaii and Etna whose lavas are relatively fluid. Lava flows might form either as primary flows directly flowing out of a vent from the vent or by rapid aggregation of hot fluid spatter that fall back from lava fountains to form a flow.
The appearance of lava flows can vary greatly with chemistry, flow rate, strain rate, temperature, viscosity and other factors. The most simple division can be made between aa lava that usually has a blocky appearance, since the surface of the flow breaks into spiny or blocky pieces, and pahoehoe lava flows, which form a smooth surface and often produce spectacular ropy textures. -> See whole entry

lava fountain

Volcanology
Lava fountain on Etna volcano (June 24, 2001)
Lava fountain on Etna volcano (June 24, 2001)
Lava fountain on Etna volcano  (Feb 16, 2000)
Lava fountain on Etna volcano (Feb 16, 2000)
Jets of fluid lava propelled into the air from an erupting vent, driven by expanding gasses.
Lava fountains are sustained jets of (usually very) fluid lava into the atmosphere. Lava fountains occur commonly on basaltic volcanoes such as Kilauea, or Etna.

The fountain gains its momentum by the expansion of gas bubbles that dissolve from the magma as pressure falls while it is rising in the conduit.

Heights, appearance, duration and erupted volumes of lava fountains can vary greatly. St... -> See whole entry

lava lake

Volcanology
The lava lake of Nyiragongo volcano, DRCongo (Jan. 2006)
The lava lake of Nyiragongo volcano, DRCongo (Jan. 2006)
The lava lake of Nyiragongo volcano, DRCongo (Jan. 2006)
The lava lake of Nyiragongo volcano, DRCongo (Jan. 2006)
Lava lakes are accumulations of larger volumes of liquid lava above one or several vents, usually contained within a crater on the summit of the volcano.
Volcanoes with eruptions that produce long-lasting lava lakes are relatively rare; some volcanoes are famous for their lava lakes: Kilauea (Hawaii), Erta Ale (Ethiopia), Nyiragongo (at present probably the most violent lava lake in the world, about 120 meters wide), Ambrym volcano (Vanuatu), Mt Erebus (Antarctica) and a few others with sometimes smaller lakes. -> See whole entry

lava trees

Volcanology
Lava trees on the eastern Rift zone Kilauea volcano, Hawaii
Lava trees on the eastern Rift zone Kilauea volcano, Hawaii
The lava coating around a tree trunk left by an invading liquid lava flow.
When a liquid lava flow invades a forest, often, the lava does not overthrow the larger trees, but flows around their trunks. At the very contact of the hot lava to the bark, a thin layer of the lava is quenched sufficiently to form an isolating coating around the trunk. The tree itself most often burns down slowly, eventually falling down onto the lava.

The typical lava trees are formed when af... -> See whole entry

magma

Volcanology
Molten rock within a volcano or underneath the earth's surface. Once magma reaches the surface it is called lava.

Related keywords (2):

explosive - lave

magnitude

Earthquakes
A number that characterizes the relative size of an earthquake. Different scales are used, but the most common is the logarithmic Richter scale. where most quakes are between 0 (tiny) and 9 (extremely large quake). Each step on this scale indicates a 10 fold energy increase of an earthquake. Felt quakes are normally above magnitude 2.5 on this scale.
Magnitude is based on measurement of the maximum motion recorded by a seismograph(sometimes for earthquake waves of a particular frequency), corrected for attenuation to a standardized distance.

Several scales have been defined, but the most commonly used are (1) local magnitude (ML), commonly referred to as œRichter magnitude, (2) surface-wave magnitude (Ms), (3) body-wave magnitude (Mb), and (... -> See whole entry

mainshock

Earthquakes
A mainshock is the largest earthquake in a sequence, sometimes preceded by one or more foreshocks, and almost always followed by many aftershocks.

Related keywords (2):

aftershock - foreshock

minette

Minerals
Minettes are a variety of igneous rock with phenocrysts of biotite, and with or without phenocrysts of hornblende, augite with a high diopside content, and olivine. Examples where minettes are found include the Navajo Volcanic Field of the Colorado Plateau and the Mexican Volcanic Belt, where he youngest minettes on the earth are found in the Mascota volcanic field.

mud volcano

Volcanology
Sidoarjo mud volcano (East Java)
Sidoarjo mud volcano (East Java)
Mud volcanoes are no true volcanoes, but vents that erupt mud, as fine sediemtn is squeezed upwards by prezzurized water, steam and gas escaping from deeper deposits.
A mud volcano is a vent on the surface erupting mud and gas or steam, but no lava. Mud volcanoes are usually not the result of volcanic processes, but more generally related to environments where pressurized deposits at depth occur that release gas and steam, which mixes with fine-grained sediments to form mud. Temperatures are much cooler than at volcanic processes. The largest structures are 10 ... -> See whole entry

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