Get our newsletter!
Check out our volcano tours on VolcanoAdventures.com!
Volcanoes & Earthquakes - new app for Android
Guaranteed tours
8-16 May 2021: From Stromboli to Etna - Sicila and Eolian Islands (Italy)
: spaces available / : guaranteed / : few spaces left / : booked out

Geology glossary

Search for term:

< Previous  Page 1  Page 2  Page 3  Page 4  Page 5  Page 6  Page 7  Page 8  Page 9  Next >

focusSynonym of: hypocenter

Earthquakes
Epicenter and hypocenter of an earthquake (Source: USGS earthquake glossary)
Epicenter and hypocenter of an earthquake (Source: USGS earthquake glossary)

foreshock

Earthquakes
Foreshocks are smaller earthquakes that precede the largest earthquake in a series, which is termed the mainshock. Not all earthquakes arre preceded by foreshocks.

Related keywords (2):

aftershock - mainshock

fossile

Geology
Fossils are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms.
Fossils (from Latin fossus, literally "having been dug up") are the mineralized or otherwise preserved remains or traces (such as footprints) of animals, plants, and other organisms. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous (fossil-containing) rock formations and sedimentary layers (strata) is known as the fossil record. The study of fossils a... -> See whole entry

granite

Volcanology
Pink granite (image: Friman / Wikimedia Commons)
Pink granite (image: Friman / Wikimedia Commons)
Granite is the most well-known and one of the most common intrusive magmatic (plutonic) rock type. It is formed when an intrusion of viscous magma with high silica content (68-75 wt %) remains under the surface of the earth, where it cools and crystallizes slowly inside the crust.
Granite is the equivalent of its extrusive (volcanic) rock type rhyolite. It is granular and coarse-grained in texture. Its principal minerals are feldspars, quartz, and mica.

Granites can be predominantly white, pink, or gray in color, depending on their mineralogy. -> See whole entry

hauyn

Minerals: hauyn crystals
Hauyn crystals from the German volcano Laacher See (photo: Stefan Wolfsried)
Hauyn crystals from the German volcano Laacher See (photo: Stefan Wolfsried)
Hauyn is a blue mineral, found f.e. in the pumice of the Laacher See eruption in Germany
Hauyne, haüyne or hauynite is a tectosilicate mineral with sulfate and chloride with formula: (Na,Ca)4-8Al6Si6(O,S)24(SO4,Cl)1-2. It is a feldspathoid and a member of the sodalite group. Hauyne crystallizes in the isometric system forming translucent, vitreous typically twinned crystals with highly variable color (blue, white, grey, yellow, green, pink). It has a Mohs hardness of 5 to 6 and a spec... -> See whole entry

Hawaiian eruption

Volcanology
Lava fountain more than 1,000 ft tall from Mauna Ulu, a vent of Kilauea Volcano in Hawaii, on 22 Aug 1969, a spectacular example of a Hawaiian eruption. Photo by D.A. Swanson, HVO / USGS
Lava fountain more than 1,000 ft tall from Mauna Ulu, a vent of Kilauea Volcano in Hawaii, on 22 Aug 1969, a spectacular example of a Hawaiian eruption. Photo by D.A. Swanson, HVO / USGS
During a Hawaiian eruption, very fluid, basaltic lava is erupted from the vent as lava fountains and forms lava flows. The fountains are driven by the expanding gasses that were contained in the magma and leave the vent as a jet. Such eruptions are common for hot-spot volcanoes such as Kilauea on Hawai'i.
The lava fountains can reach heights of several hundreds meters, sometimes even more than 1 km. They can last for hours or even days and often occur from fissure vents to form so-called curtains of fire.

The lava spatter that falls back from the fountain can form lava flows if it is still fluid enough, or build up welded spatter ramparts and cinder cones around the vent. Along with the lava foun... -> See whole entry

hornito

Volcanology
Erupting hornito on Kilauea volcano (Hawaii)
Erupting hornito on Kilauea volcano (Hawaii)
Erupting hornito on Etna volcano (Italy)
Erupting hornito on Etna volcano (Italy)
Hornito (Spanish) = "Little oven".

Volcanic hornitos are small (usually a few meters high) rootless spatter cones that form on the surface of a (usually basaltic pahoehoe) lava flow. A hornito develops when lava is forced up through an opening in the cooled surface of a flow (a skylight) and then accumulates around the opening. Typically, hornitos are steep sided and form conspicuous pinnacles o... -> See whole entry

hypocenter

Earthquakes
Epicenter and hypocenter of an earthquake (Source: USGS earthquake glossary)
Epicenter and hypocenter of an earthquake (Source: USGS earthquake glossary)
When talking about earthquakes, the hypocenter or focus is the point inside the earth where an earthquake rupture starts. It is often confused with epicenter, which is the is the point directly above it at the surface of the Earth, where the quake is usually felt most strongly.

Related keywords (1):

epicenter

lava

Volcanology
Lava poors out from several vents inside the crater of Pu'u 'O'o, Kilauea volcano, Hawai'i
Lava poors out from several vents inside the crater of Pu'u 'O'o, Kilauea volcano, Hawai'i
Molten rock, called magma, is called lava when it reaches the surface during a volcanic eruption. Depending on how the magma erupts, it can form lava flows, lava fountains, lava lakes, or be fragmented into scoria and ash during explosive eruptions.
In a wider use of the term, also the cooled and solidified products of erupted magma are called lava (in form of coherent lava flows, or fragmented tephra).



Magma when it erupts as lava is almost never a completely molten rock, but contains 3 phases: liquid, solid mineral crystals (xenoliths) and gas bubbles, mainly water and carbon dioxide.

The temperature of erupted lava ranges from around ... -> See whole entry

lava balloon

Volcanology
Steaming lava blocks on 27 Nov 2011 near La Restinga (El Hierro) photographed from the air by Guardia Civil / INVOLCAN
Steaming lava blocks on 27 Nov 2011 near La Restinga (El Hierro) photographed from the air by Guardia Civil / INVOLCAN
Lava balloons are hollow gas-filled pieces of lava floating to the surface above effusive submarine vents. Many lava balloons have been produced and observed during the ongoing 2011-12 shallow submarine eruption at El Hierro.
Floating lava blocks could result from the detachment of pillow-lava edges followed by the ascent of blocks with sufficient gas content. It is also possible that hot, gas-rich lava fragments result from small submarine lava lakes or fountains.

A thin frozen skin of lava seals the gas cavity, and the block might then rise as a hot lava balloon. During ascent, the gas exsolves and nucleates inside ... -> See whole entry

< Previous  Page 1  Page 2  Page 3  Page 4  Page 5  Page 6  Page 7  Page 8  Page 9  Next >

 

More on VolcanoDiscovery

 
Why is there advertising on this site?
Copyrights: VolcanoDiscovery and other sources as noted.
Use of material: Most texts and images, in particular photographs, on this website are protected by copyright. Further reproduction and use of without authorization is usually not consented. If you are not sure or need licensing rights for photographs, for example for publications and commercial use, please contact us.
Home | Travel | Destinations | Volcanoes | Photos | Earthquakes | About | Glossary | News | Contact | Privacy | Imprint || Français | Deutsch
Follow us: