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Geology glossary

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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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