Geology glossary

Tephrite is an type of volcanic (extrusive) rock with low silica content, similar to basalt, but containing foid minerals (e.g. nephelinite, leucite) along with plagioclase.
The composition of tephrite is called tephritic.

Tephritic refers to the mineral composition of tephrite, an type of volcanic (extrusive) rock with low silica content, similar to basalt, but containing foid minerals (e.g. nephelinite, leucite) along with plagioclase.

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From Latin "tumulus" = "little hill", tumuli (pl.) are uplifted sections of pahoehoe lava crust caused by pressure from still fluid lava accumulating beneath the hardened crust.

Tumuli are a characteristic feature of all pahoehoe lava flow fields, such as prominent on Kilauea volcano, Hawaii, but also many other basaltic volcanoes including Etna. Read all

Volcanic Ash Advisory Centers (VAAC) are research centres who monitor volcanic ash clouds in real time. Each time, a volcano erupts a significant ash cloud, short reports are issued and transmitted directly to air control centres. The 9 VAAC are located in London, Toulouse, Tokyo, Darwin, Anchorage, Washington, Montreal and Buenos Aireas and collectively cover most of the globe.

The Volcanic Ash Advisory Centers (VAAC) are groups of experts and government-funded bodies to montor volcanic ash clouds all over the planet in real time. As Europe experienced in April 2010, volcanic ash clouds are hazardous for aircraft and must be avoided to fly through, even if that means cancellation of flights.

As of 2010, there are 9 VAAC located in different areas and each focussing m... Read all

The ability of a liquid to flow. Basalt magma has a relatively low viscosity making it runny, whereas rhyolite magma has a high viscosity making the magma thick and sticky.

Pathways of rising magma inside vertical fissures.

Dikes are imaginable as the veins of a volcano, the pathways of rising magma. A dike is called a -usually more or less vertical- flat, sheet-like magma body that cuts unconformingly through older rocks or sediments.

Most dikes can be described as fractures into which magma intrudes or from which they might erupt. The fracture can be caused by the intrusion of pressurized magma, or vice versa, ... Read all

Volcanic tremor is a continuous seismic signal with regular or irregular sine wave appearance and low frequencies (0.5-5 Hz).

Volcanic tremor is usually in the form of harmonic tremor which has a very uniform appearance, whereas spasmodic tremor is pulsating and consists of higher frequencies with a more irregular appearance.
Tremor can be caused by different processes inside the volcano, including resonance triggered by magma flowing through cracks and vents, or continuous low-frequency earthquakes so closely spaced th... Read all

A volcaniclastic rock or loose deposit made of (older) volcanic fragments.

The science of studying volcanoes.

Volcanology comprises the study of volcanoes and volcanic phenomena and is mostly regarded as a sub-part of geology, but is interwoven with other science disciplines as well: chemistry, physics, but also sociology, history, archaeology. Read all