tsunami - large waves formed by large undersea landslides commonly caused by earthquakes. From the Japanese word for seismic sea wave. (misnamed tidal wave, though it has nothing to do with tides.)
tuff - volcanic ash hardened by pressure or from natural cements deposited from water that seeps through the ground.
volcanic - pertaining to a volcano
volcaniclastic - refers to the clastic rocks composed of volcanic particles.
volcanic ash - fragmental pieces of glass, vcrystals, and rock fragments, less than 0.4 inchin diameter, extruded by volcanoes.
volcanic sandstone - a rock composed mostly of sand0sized volcanic particles.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
Wednesday, March 9, 2011
Monday, March 7, 2011
Worlds Most Active Volcanoes
Stromboli
Kilauea
Yasur
Etna
Christian Science Monitor: World's Most Active Volcnaoes
Mount Merapi, located near Yogyakarta, Indonesia, is one of the country's most volatile volcanoes. It began erupting at dusk on Tuesday [March 1, 2011), and thousands evacuated the area surrounding it. It didn't come as a shock, as scientists have been expecting an eruption for a while.
Here are some of the world's most active volcanoes.
4. Stromboli (Italy)
Stromboli is the name of both a small island northwest of Sicily and the volcano that made it. The volcano has been erupting regularly, but mildly, for about 2,000 years and its nighttime explosions have made it a major tourist attraction. While minor eruptions occur about every 10 to 20 minutes, Stromboli also has had some more serious eruptions that have prompted evacuations or deaths, mainly from debris. However, because eruptions mostly happen near the summit, about 700 people are able to make a home on the island. Its last major eruption happened in July 2010.
3. Mount Yasur (Vanuatu)
Located in the southwest Pacific on Tanna Island in Vanuatu, Mount Yasur is part of the Pacific Ring of Fire, a string of volcanoes. It erupts almost constantly, with most measurements indicating an eruption several times an hour for several centuries. Because of the almost constant volcanic activity it is a popular tourist destination. Sometimes tourists are able to climb all the way to the summit. Mt. Yasur has been nicknamed "The Lighthouse of the Pacific" because it is constantly alight from eruptions.
2. Kilauea (Hawaii)
Kilauea, located on Hawaii's Big Island, has erupted uninterruptedly since 1983 and nearly constantly for as long as records have been kept. It is Hawaii's most active volcano and 70 percent of its surface is less than 600 years old. The eruption that began in 1983 has steadily added coastline to the island.
1. Mount Etna (Italy)
Mount Etna, located in Sicily, Italy, is Europe's largest volcano and one of its most active. Records of vulcanism date to 1500 BC. It erupts in several different ways and places, making it unpredictable for those living in the area. It is almost 11,000 feet tall, though it's precised altitude is in constant flux because of eruptions and other disturbances, and much of its surface is lava from previous eruptions.
7 Mar, 2011: Why did Hawaii's Kilauea volcano shoot lava 80 feet into the air?
Christian Science Monitor: Why did Hawaii's Kilauea volcano shoot lava 80 feet into the air?
A cinder cone brimming with a lava lake, on the flank of Hawaii's Kilauea volcano, appeared to drain suddenly over the weekend, its molten rock apparently finding outlet in a new fissure that opened farther down slope.
The cone, named Pu'u 'O'o, saw its "floor" plunge 370 feet as the lava beneath found a weak area in Kilauea's flank. The floor actually a thin crust of cooler material that sits atop the molten rock like skin on pudding.
In addition, lava-lake levels in Halema'uma'u Crater, which sits inside the large caldera at the top of Kilauea, dropped significantly as well, according to scientists at the US Geological Survey's Hawaii Volcano Observatory. The observatory is perched near the caldera's edge.
With Pu'u 'O'o as an outlet, Kilauea has been erupting non-stop since 1983, giving scientists and tourists alike a window on how Earth replenishes the thin skin of rock that makes up the planet's crust.
The opening of the crack on Saturday "is quite an exciting development," says James Deiterich, a geophysicist at the University of California at Riverside who studies Hawaii's volcanoes. "For several years the eruption has been very boring. There's been no change in its pattern at all" – just lava slowly rising and falling as Pu'u 'O'o went through its paces.
Dr. Deiterich explains that while he hasn't seen much of the data yet from the weekend breakout, the event appears to be common to volcanoes of Kilauea's type – a so-called shield volcano.
Shield volcanoes tend to ooze relatively thin, gas-poor lava over the tops of their craters or through fissures that open along their flanks as magma pushes up, causing the slopes to develop cracks. Regions where the cracks appear are known as rift zones. Pu'u 'O'o is the most active outlet in Kilauea's eastern rift zone.
The slope where the fissure appeared has been building a bulge for some time, Deiterich says.
Given a choice, lava would rather take the path of least resistance – like a weak spot lower on the slope – than continue to push its mass vertically to overtop the cinder cone's throat.
Although shield-volcano eruptions can generate spectacular fountains of lava – in the case of this weekend's plumbing change, up to 80 feet high – the eruptions tend to be tame compared with the violent blasts from steeper-sloped stratovolcanoes, such as those found in Indonesia, Chile, or the Pacific Northwest, for instance.
Magmas in these volcanoes tend to be a thicker mix of material and richer in gases, leading to explosive eruptions.
Although lava can overtop a stratovolcano's summit as well, the thicker molten goo doesn't travel as far from the cone as does the thinner lavas from shield volcanoes – a trait that gives the shield volcanoes their wide, low-slung look.
But the look can be deceiving. Kilauea's large sibling, Mauna Loa, rises to just over 13,700 feet above sea level. The mountain's roots lie some 16,400 feet below sea level, making it, as well as its slightly taller sister, Mauna Kea, taller than Mt. Everest.
For its part, Kilauea marks the most active part of a hot spot in Earth's crust that is thought to have formed the Hawaiian island chain during the past 28 million years. Researchers say the hot spot consists of a long-lasting plume of magma beneath a weak patch of undersea crust. Magma breaching the crust formed undersea volcanoes, which slowly grew until they could poke above sea level. Hawai'i's volcanoes sit far from the boundaries of crustal plates, where the bulk of Earth's volcanic activity takes place.
Scientists still argue over whether the chain was created as the Pacific Plate moved over the hot spot to give the chain its follow-the-leader pattern or whether the hot spot itself does some of the moving.
A cinder cone brimming with a lava lake, on the flank of Hawaii's Kilauea volcano, appeared to drain suddenly over the weekend, its molten rock apparently finding outlet in a new fissure that opened farther down slope.
The cone, named Pu'u 'O'o, saw its "floor" plunge 370 feet as the lava beneath found a weak area in Kilauea's flank. The floor actually a thin crust of cooler material that sits atop the molten rock like skin on pudding.
In addition, lava-lake levels in Halema'uma'u Crater, which sits inside the large caldera at the top of Kilauea, dropped significantly as well, according to scientists at the US Geological Survey's Hawaii Volcano Observatory. The observatory is perched near the caldera's edge.
With Pu'u 'O'o as an outlet, Kilauea has been erupting non-stop since 1983, giving scientists and tourists alike a window on how Earth replenishes the thin skin of rock that makes up the planet's crust.
The opening of the crack on Saturday "is quite an exciting development," says James Deiterich, a geophysicist at the University of California at Riverside who studies Hawaii's volcanoes. "For several years the eruption has been very boring. There's been no change in its pattern at all" – just lava slowly rising and falling as Pu'u 'O'o went through its paces.
Dr. Deiterich explains that while he hasn't seen much of the data yet from the weekend breakout, the event appears to be common to volcanoes of Kilauea's type – a so-called shield volcano.
Shield volcanoes tend to ooze relatively thin, gas-poor lava over the tops of their craters or through fissures that open along their flanks as magma pushes up, causing the slopes to develop cracks. Regions where the cracks appear are known as rift zones. Pu'u 'O'o is the most active outlet in Kilauea's eastern rift zone.
The slope where the fissure appeared has been building a bulge for some time, Deiterich says.
Given a choice, lava would rather take the path of least resistance – like a weak spot lower on the slope – than continue to push its mass vertically to overtop the cinder cone's throat.
Although shield-volcano eruptions can generate spectacular fountains of lava – in the case of this weekend's plumbing change, up to 80 feet high – the eruptions tend to be tame compared with the violent blasts from steeper-sloped stratovolcanoes, such as those found in Indonesia, Chile, or the Pacific Northwest, for instance.
Magmas in these volcanoes tend to be a thicker mix of material and richer in gases, leading to explosive eruptions.
Although lava can overtop a stratovolcano's summit as well, the thicker molten goo doesn't travel as far from the cone as does the thinner lavas from shield volcanoes – a trait that gives the shield volcanoes their wide, low-slung look.
But the look can be deceiving. Kilauea's large sibling, Mauna Loa, rises to just over 13,700 feet above sea level. The mountain's roots lie some 16,400 feet below sea level, making it, as well as its slightly taller sister, Mauna Kea, taller than Mt. Everest.
For its part, Kilauea marks the most active part of a hot spot in Earth's crust that is thought to have formed the Hawaiian island chain during the past 28 million years. Researchers say the hot spot consists of a long-lasting plume of magma beneath a weak patch of undersea crust. Magma breaching the crust formed undersea volcanoes, which slowly grew until they could poke above sea level. Hawai'i's volcanoes sit far from the boundaries of crustal plates, where the bulk of Earth's volcanic activity takes place.
Scientists still argue over whether the chain was created as the Pacific Plate moved over the hot spot to give the chain its follow-the-leader pattern or whether the hot spot itself does some of the moving.
Volcano Glossary Part 6
sandstone - a sedimentary rock formed of cemented grains with diameters less than .04 inches.
sedimentary - refers to various aspects of sediments, which are layered deposits of rock and mineral particles.
scoria - a rough-surfaced pyroclastic fragment, baseball to nut size, formed directly from magma and explosively ejected to the surface. It is gaseous and therefore has many bubbles (vesicles) form within the viscous material; synonymus with cinder.
seismograph - a machine that records the intensity of earthquakes.
spatter cone - a small cone made of hot, gas-rich bombs of fluid basalt lava that fall and stick together around a vent.
strata - layers of rock are said to be stratified and are referred to in the plural as stra; an individual layer is a stratum.
Strombolian eruption - an eruption that produces high-arcing incandescent "rooster tails", reminiscent of colorful, fireworks fountains. The ejecta are mainly basaltic cinders and bombs that construct cinder cones. (Named after the Stromboli volcano on the island of Stromboli, off the north coast of Sicily, which erupts in this way.)
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
sedimentary - refers to various aspects of sediments, which are layered deposits of rock and mineral particles.
scoria - a rough-surfaced pyroclastic fragment, baseball to nut size, formed directly from magma and explosively ejected to the surface. It is gaseous and therefore has many bubbles (vesicles) form within the viscous material; synonymus with cinder.
seismograph - a machine that records the intensity of earthquakes.
spatter cone - a small cone made of hot, gas-rich bombs of fluid basalt lava that fall and stick together around a vent.
strata - layers of rock are said to be stratified and are referred to in the plural as stra; an individual layer is a stratum.
Strombolian eruption - an eruption that produces high-arcing incandescent "rooster tails", reminiscent of colorful, fireworks fountains. The ejecta are mainly basaltic cinders and bombs that construct cinder cones. (Named after the Stromboli volcano on the island of Stromboli, off the north coast of Sicily, which erupts in this way.)
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
Saturday, March 5, 2011
Volcano Glossary Part 4
Maar - a small volcano with wide diameter relative to its height, often with a bowl-shaped crater.
magma - molten rock with contained gases that forms within or somewhat below the earth's crust. It is ejected in highly explosive eruptions to form pyroclasts or lava flows.
magmatic eruption - an explosive eruption from the sudden expansion of magma from internal gas pressure.
nuèe ardente - a hot, heavier-than-air, turbulent "volcanic hurricane" composed of a mixture of hot gases and solid particles. Nuèes ardentes flow rapidly down the slopes of a volcano, ofren attaining speeds fifty to one hundred miles an hour.Such flows commonly form in two parts, a lower "glowing avalance" and an upper "glowing cloud."
pahoehoe lava - lava that has a smooth surface after cooling, compared with the roughness of aa.
Pelèan eruption - an eruption that produces a nuèe ardente, such as that at Mount Pele in 1902.
Plinian eruption - an eruption that forms ash clouds above the volcano to heights as much as thirty miles into the atmosphere. (Named after the eruption of Mount Vesuvius in 72 AD that killed Pliny the elder.)
pumice - a glass foam formed by frothing gas-rich magma. Pumice is very light weight and can float in water.
pyroclastic - refers to the fragmental materials formed by explosive processes of volcanoes.
pyroclastic flow: a heavier-than-air, hurricane-like, non-turbulent cloud of volcanic particles mixed with hot gases, more dense than a pyroclastic flow.
pyroclastic surge - a heavier-than-air, hurricane-like, turbulent cloud of volcanic particles mixed with hot gases, less dense than a pyroclastic flow.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
magma - molten rock with contained gases that forms within or somewhat below the earth's crust. It is ejected in highly explosive eruptions to form pyroclasts or lava flows.
magmatic eruption - an explosive eruption from the sudden expansion of magma from internal gas pressure.
nuèe ardente - a hot, heavier-than-air, turbulent "volcanic hurricane" composed of a mixture of hot gases and solid particles. Nuèes ardentes flow rapidly down the slopes of a volcano, ofren attaining speeds fifty to one hundred miles an hour.Such flows commonly form in two parts, a lower "glowing avalance" and an upper "glowing cloud."
pahoehoe lava - lava that has a smooth surface after cooling, compared with the roughness of aa.
Pelèan eruption - an eruption that produces a nuèe ardente, such as that at Mount Pele in 1902.
Plinian eruption - an eruption that forms ash clouds above the volcano to heights as much as thirty miles into the atmosphere. (Named after the eruption of Mount Vesuvius in 72 AD that killed Pliny the elder.)
pumice - a glass foam formed by frothing gas-rich magma. Pumice is very light weight and can float in water.
pyroclastic - refers to the fragmental materials formed by explosive processes of volcanoes.
pyroclastic flow: a heavier-than-air, hurricane-like, non-turbulent cloud of volcanic particles mixed with hot gases, more dense than a pyroclastic flow.
pyroclastic surge - a heavier-than-air, hurricane-like, turbulent cloud of volcanic particles mixed with hot gases, less dense than a pyroclastic flow.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
Thursday, March 3, 2011
Volcano Glossary Part 3
ignimbrite - a deposit of a pyroclastic flow or pyroclastic surge or both.
lapilli - pyroclastic particles ranging in size from .04 to 2.6 inches.
laterite - soil so rich in iron oxide that it may be mined as an iron ore.
lava - a volcanic effusion of molten rock that flows upon the ground, also solidified lava.
limestone - a rock composed of an aggregate of calcium carbonate minerals.
littoral cone - a mound of volcanic particles formed when hot lava mixes with water at the shoreline of a body of water and explodes. The mound is a cone that looks like a volcano but has no underground vent.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
lapilli - pyroclastic particles ranging in size from .04 to 2.6 inches.
laterite - soil so rich in iron oxide that it may be mined as an iron ore.
lava - a volcanic effusion of molten rock that flows upon the ground, also solidified lava.
limestone - a rock composed of an aggregate of calcium carbonate minerals.
littoral cone - a mound of volcanic particles formed when hot lava mixes with water at the shoreline of a body of water and explodes. The mound is a cone that looks like a volcano but has no underground vent.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
Tuesday, March 1, 2011
Volcano Glossary Part 2
caldera - a crater larger than five miles in diameter formed by collapse of the ground or volcano into an underground cavity formed by the ejection of an equivalent amount of pyroclastic material. Some calderas are more than 40 miles in diameter.
cinder - a rough-surfaced pyroclastic fragment baseball to nut size, formed directly from magma and explosively ejected to the surface. It is gaseous and therefore many bubbles (vesicles) form within the viscous material. Synonymous with scoria.
cinder cone - a volcano formed by cinders that pile up around an active vent.
cross beds - a bed of layered laminations (very thin layers) truncated by other layers across eroded edges within a larger layer, or within an assemblage of layers.
dome - a dome-shaped protrustion of solidified magma formed by slow extrusion of highly viscous magma located on the side of, or within, the crater of a volcano.
ejecta - Pyroclastic material explosively ejected from a volcano.
fallout - Acumumlation of pyroclastic material that falls from the sky.
fumarole - a vent from which gases form magma - or steam created by hot magma-heating water-escape into the atmosphere.
hydrovolcanic eruption - an explosion or eruption caused by sudden expansion of water when mixed with magma.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
cinder - a rough-surfaced pyroclastic fragment baseball to nut size, formed directly from magma and explosively ejected to the surface. It is gaseous and therefore many bubbles (vesicles) form within the viscous material. Synonymous with scoria.
cinder cone - a volcano formed by cinders that pile up around an active vent.
cross beds - a bed of layered laminations (very thin layers) truncated by other layers across eroded edges within a larger layer, or within an assemblage of layers.
dome - a dome-shaped protrustion of solidified magma formed by slow extrusion of highly viscous magma located on the side of, or within, the crater of a volcano.
ejecta - Pyroclastic material explosively ejected from a volcano.
fallout - Acumumlation of pyroclastic material that falls from the sky.
fumarole - a vent from which gases form magma - or steam created by hot magma-heating water-escape into the atmosphere.
hydrovolcanic eruption - an explosion or eruption caused by sudden expansion of water when mixed with magma.
Bibliography
Out of the Crater: Chronicles of a Volcanologist, Richard V. Fisher, Princeton University Press, 1999
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