Term
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Definition
| Volcanic plateau built of basaltic lava erupted from a hot spot below the mid-Atlantic Ocean spreading center. |
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Term
| Where does most of the volcanism on Earth take place? |
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Definition
Oceanic ridge systems where seafloor spreading occurs. (Almost all volcanic activity takes place below sea level.
-Solid, but hot and ductile, mantle rock rises upward into regions of lower pressure. |
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Term
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Definition
Eruptions on small island of Heimaey caused lava flow that damaged 300 buildings, and pyroclastic material burried another 30. Icelander's help limit damage by:
-bulldozing pyroclastic material to create barriers the diverted and controlled lava flows and dense volcanic gases.
-Sprayed sea water on the lava flows, causing rapid cooling and hardening, reshaping the harbor.
-created a pipe system that poured water over the cooling lava.
-Return pipes were installed to bring the heated water (169 degrees) into town to heat building. |
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Term
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Definition
| 2000 ft of the Vatnajokull (covers 10% of Iceland) glacier was melted due to the rising magma caused by earthquake activity. Meltwater flowed under the glacier and accumulated in the caldera of Grimsvotn volcano. It accumulated around 1 mile worth of volume which raised the glacier up, and flooded the surrounding area. It was the second largest river in the world for 2 days, destroying Iceland's longest bridge, telephone lines, and a road. |
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Term
Subduction Volcanoes
*Biggest impact on humans because they're heavily populated. |
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Definition
| Galeras (Colombia), Mount Unzen (Japan), Mounts Pinatubo and Mayon (Philippines), Mount St. Helens (Washington state), and Soufriere Hills on Montserrat. |
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Term
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Definition
March, 1980. Killed 62.
- Dozens of earthquakes in the days leading up to the major eruption, causing magma to rise to the surface.
- Top 1,313 of cone was blown off.
- Magma filled "bulge" weakened and fell in an avalanche measuring as a 5 magnitude earthquake.
-Lahars formed and flowed down the river, mixing with water from melted snow and ice, taking large amounts of debris with it. This caused a drop in pressure, resulting in a blast.
- pyroclastic flow containing volcanic gases, solid rock fragments, magma bits, and splintered trees traveled 210 miles.
-The blast exposed the effervescing magma body. rapidly escaping gases blew upward, carrying small pieces of magma. - Boiling gases carried ashes about 1/4 mile away. * wind carried ashes all over US.
-Volcano is currently rebuilding, and hasn't erupted recently because it lost most of its volatiles during the last eruption. |
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Term
| Lassen Peak, CA (1914-1917) |
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Definition
Large lava dome, formed because it's magma is too poor in volatiles and too viscous to flow away, so it oozes upward.
- May 1914, numerous smaller eruptions culminated with a large episode that sent an ash cloud up over 11,000 ft high.
- May 1915, volcano overflowed with water-deficient, sticky magma. The magma was to viscous to flow over the lip, so the top of the volcano started to give way causing lahars.
- North slope split, causing a pyroclastic flow.
- May 22, 1914 a mushroom cloud of ash blasted 5 miles high. |
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Term
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Definition
- 14,162 ft in elevation, the second tallest of the Cascade Range volcanoes.
- Third tallest is Mount Shastina, which sits on it's shoulder.
- Active volcanoes which have erupted 11 times in the last 3,400 years.
- Because of the topography of the base of the volcanoes, the broad and smooth land allows pyroclastic flows to spread widely as they move down the volcano flank. |
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Term
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Definition
- Subduction caused Stratovolcano
- Since 1616 more than 1,500 people have been killed during 40 recorded deadly eruptions.
- Pyroclastic flows roll down mountains, sending pyroclastic material, hot gas, and intermixed air up in to cooler air providing time for heat to dissipate and for pyroclastics to cool and be spread. |
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Term
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Definition
- Most deadly pyroclastic-surge
- Numerous earthquakes caused a plinian eruption, blasting rock and magma into the atmosphere.
- Followed by a surge flowing radically outward for 5 miles, wiping out 9 villages, killing 2,000 people.
- Plinian shot up 12 miles, sending sulfur dioxide into the upper atmosphere, causing a global climate change. |
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Term
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Definition
Ring shaped base surges that occur when more steam and less pyroclastic material combine to produce to a more-dilute, less-dense, high velocity flow.
- Not stopped by bodies of water |
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Term
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Definition
- Growing lava dome provides steady magma supply and upward life of unstable, everchanging topography.
- Large chunks of lava dome frequently break off and create pyroclastic flows.
- caused tsunami, killing 15,000 people. |
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Term
| Mont Pelee, Martinique, 1902 |
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Definition
- Pelee means bald or peeled because volcanism destroyed all plant life during eruptions in 1792.
- Crater on top of volcano filled with viscous magma and kept plugging the crater.
- Tiny gas bubbles exploded and pyroclastic flows blew gases and flowing volcanic fragments into the air.
Energy sources were: initial blast, gravity, and gas continuing to escape from the pieces of airborn magma. |
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Term
| Ways to die from Pyroclastic flow |
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Definition
- Physical impact
- inhaling super hot gas
- burns |
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Term
| Kelut, Indonesia, 1586 and 1919 |
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Definition
- Stratovolcano with a crater lake at its summit.
- Lake water combines with loose pyroclastic materials forming fast moving lahars (moving 60 mph)
- Lahars traveled up to 24 miles, and killed 5,000 people. |
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Term
| Nevado Del Ruiz, Colombia, 1985 |
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Definition
- Earthquakes caused Plinian eruptions, which melted the ice cap on top of the volcano, causing lahars to travel down the side of the mountain onto surrounding towns.
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Term
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Definition
- Tallest of Cascade Range volcanoes. Extremely dangerous because of its height, extensive glacial cap, frequent earthquakes, and its active hot-water springs which have weakened the mountain internally.
- Supports the largest glacier system of any mountain in the lower 49 states. |
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Term
| Laki, Iceland, Fissure Eruption of 1783 |
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Definition
- 1783, greatest lava eruption of historic times.
- Fissure opened and basaltic lavas gushed for 50 days, covering an area of 218 miles.
- High concentration of fluorine and sulfur dioxide caused death to animals and caused a famine to Icelandic people, rsulting in 10,000 deaths. |
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Term
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Definition
- Most violent and explosive eruption of the last 200 years.
- Plinian eruption column shot up 20 miles, carrying pumice.
- Second eruption caused magma to erode and weaken the vent in the volcano.
- Weakened vent poured magma and pyroclastic flows, cutting down the elevation of the mountain from over 4,000 feet, to just over 2,000 feet, devastating crops, leading to famine and the spread of disease.
- Killed at least 117,000 people.
- 10% killed by eruption
- 90% caused by chain reactions |
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Term
| Killer Lakes of Cameroon, Africa |
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Definition
- Lake Nyos, topographically high crater lake was filled with gas belched from beneath the basaltic magma.
- Toxic carbon dioxide caused asphyxiation and death to 37 people, and death to animals. |
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Term
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Definition
| Rifts that don't open up enough to become spreading centers. |
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Term
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Definition
- Magma rises in the rifts between East Africa and the African continent, thus building stratovolcanoes.
- Lava lake at its summit crater.
- Lava flowing down the slopes killed more than 45 people.
- Flow depends on viscosity and topography of the land. |
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Term
| Volcanic Explosivity Index |
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Definition
| Estimates the magnitude of explosive eruptions based on volume of material erupted, and eruption column height. |
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Term
| Mount Pinatubo, Philippines, 1991 |
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Definition
| Volcano warning success story! Magma in the volcano moved upward, causing small earthquakes, which were monitored and aided in the evacuation efforts of the nearby towns. Only 300 were killed, when an estimated 20,000 could have died. |
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Term
| Signs of impending eruption |
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Definition
Seismic waves- breaking rock and flowing magma sends off short-period seismic waves, which are measured.
Ground deformation- grounds rise and sink as magma moves up or withdraws. Can be measured with satellites using radar, electronic distance, strain, and tilt meters are used.
Gas measurements- as magma rises to the surface, pressure is relieved and gases escape. Either increase or decrease could be bad. |
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Term
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Definition
| US Geological Survey established a Volcano Hazard Program including 5 volcano observatories: Alaska (AVO), Cascades (CVO), Hawaiian (HVO), Long Valley (LVO), and Yellow Stone (YVO). Each records and publishes current activity. |
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