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Definition
| low viscosity (more fluid) because of low silica content; low gas content. |
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| More explosive because magma can't flow out, thicker lava compared to basaltic, |
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Definition
| Associated with Plinian eruptions! More viscous so more resistant to flow. |
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Definition
| low gas content, quiet eruptions |
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Term
| How do magma properties influence eruptions? |
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Definition
| The more viscous and the higher the gas content, the more explosive the eruption will be (rhyolite and dacite) |
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Term
| How are magmas formed in the Earth’s crust and mantle? |
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Definition
| Mantle that is less dense than mantle around it starts to rise, heats up and melts, forms magma chamber under volcano |
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Definition
| classic volcano. Layers of lava and ash which look like mountains. EG: SAINT HELEN'S |
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| Usually only erupt once, so this forms a single cone from the explosive matter. EG: Ojo de Agua |
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| Made of fluid basalt lava flows, which are able to travel much farther. This creates the long shield-like shape. EG: MUANA KEA. |
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Definition
| hot spots where lava and steam come out of cracks in the ground. EG: Iceland, Idaho |
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Definition
| larger cataclysmic eruptions which occur when hot magma reacts violently with shallow water. EG: Crater Lake |
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| Why do volcanoes have different forms? |
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Definition
| Viscosity and kind of magma, which flow out and produce the volcano's shape. |
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| Where do volcanoes occur? |
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Definition
Plate margins
Spreading margins
mid ocean ridges (Iceland)
rifting continents (E Africa)
Converging
Island arcs (Japan)
Contintental margins (Andes)
Plate interiors
Oceanic plates (Hawaii)
Continental plates (Yellowstone) |
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Definition
| Least eruptive, smallest volume of material (form shield volcanoes). Characteristics: molten magma, fire fountaining (constant non violent flow), lava flows, cinder. HAWAII |
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Definition
| More explosive but less material; associated with steam. Characteristics: hot magma reacts with water, causing steam explosions |
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Definition
| More eruptive, more material. Characteristics: molten magma, but more eruptive than Hawaiian. MOUNT ETNA |
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Definition
| Steam-blasts of old rock; fairly explosive but don't erupt any new material. Steam results from magma heating up ground water. MT ST HELENS |
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Definition
| most eruptive, most material, most destructive. PINATOBO |
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Term
| 90% of all lava flows are...? |
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Definition
| Basaltic. The more silica-rich magma tends to explode more violently and fragment. |
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Term
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Definition
| has a shiny, glassy surface. It tens to be more fluid (lower viscosity), so it flows more quickly and produces thinner flows |
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Definition
| most common, rubbly flow with higher viscosity therefore moves more slowly and produces thicker flows |
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Definition
| thickest flow so it travels slower (contains more dacites and rhyolites), blocky surface |
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Definition
| flow faster bc concentrating flow in one direction, tubes = crust forming under hardened lava on top, flows faster |
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Definition
| effects speed (less = faster, more = slower). |
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Definition
| volume of eruption; biggest thing effecting flow rate. |
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Definition
| shows distance and thickness of ash falls from volcano, direction shows effect of wind (how much erupted, how far it travelled) |
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Definition
| usually slow moving (except in rare cases), travel far depending on viscosity, topography, and volume of ejected material; destroy everything in path (road, buildings, agriculture); can be slowed/redirected with water (Heimay); death toll since 1600: ~900 |
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| affect the largest area around volcano; can cause roofs to collapse, damage to crops, respiratory damage and pollute water; ~11k deaths since 1600; can cause aircraft failure |
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Definition
| rapidly flowing mixture of water (from rain or melted snow), mud, volcanic debris and ash, consistency of wet cement; travel VERY FAST and can travel up to 200 miles; ~27k deaths (2nd most destructive to life); buried entire town of Armero |
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Definition
| globs of molten magma ejected into air; basaltic or andesitic; associated with Strombolian eruptions; fall within 3 miles of vent, so localized damage; can cause fires, can and have hit airplanes in Japan |
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Term
| Pyroclastic flows & surges |
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Definition
| glowing ash clouds; travel at 20-70 mph, 200-800 degrees C!!!; surges can be up to 300 mph! flow= basic process, which cause surges vs surge= specific volume of air and ash is much hotter so more unpredictable, so more hazardous; caused by collapse/explosion of magma domes or collapse of eruption column; ~55k deaths attributed to these due to asphyxiation, boiling, burning, impact from debris (ST HELENS) |
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Term
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Definition
| first recognized during ST HELENS eruption; closely associated with landslide of material from side of volcano; sudden release of pressure from side of volcano; similar to pyroclastic flows (VERY DANGEROUS); material explodes out of side!! |
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Term
| how many volcanoes are classified as "high risk"? |
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Definition
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Term
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Definition
| amount of time between eruptions of a dormant or active volcano. Between 100 and 1k are most dangerous because the pressure build up causes bigger eruptions. |
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| What info/measurements inform predictions? |
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Definition
-remote sensing
-ground defmoration
-geophysical measurements:
-gas: sometimes come out of side
-hydrology
-seismicity!!!!!: one of best ways to predict on short term; records motion under ground near volcanoes |
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| How are volcanoes monitored in real time? |
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Definition
-Green= normal state
-Yellow= may erupt, suspect one is coming
-Orange= increase in activity, small eruptions, may need to evacuate
-Red= eruption will take place in days |
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| What have been successes and failures of prediction? |
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Definition
-failure: Nevada del Ruiz when whole town was buried; local officials didn’t listen to geologists, and mudflow took out Armero
-success: Pinotubo bc near a lot of people and massive eruption but people were evacuated |
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Term
| What factors affect the designation of high-danger volcanoes? |
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Definition
| active or domant, past eruptive history, seismic activity and deformation, proximity to population |
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Term
| What are volcano hazard maps? |
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Definition
| describe areas that are most likely to experience damage in association with an eruption; higher numbers indicate more potential for damage |
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Term
| What are cataclysmic eruptions? |
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Definition
-Eruptions that are substantially larger than others; Krakatoa, Katmai, Tomb
1) volcanoes that completely blow themselves apart (Crater Lake)
2) elliptical depression (caldera) above magma resevoir
-vast volumes of rhyolite/dacite ash (Yellowstone is a potential cataclysmic) |
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Term
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Definition
| Hawaiian shield volcano, very active. Ongoing eruptions from 1983 to the present. Started from long fissures in the ground from previous eruptions. Casualties: only forest. |
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Definition
| January to June 1973. Volcanic bombs started fires and ash collapsed roofs. Lava flow destroyed homes and businesses. Government stops the flow by pumping sea water to divert the flow away from the harbor. |
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Definition
| 1991, geologists were successful in predicting eruption by using seismographs. It had a HUGE eruption column and the ash spread around the globe. People would have been killed by mud and ash flows, but were evacuated. Plinian eruption |
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Term
| Hazards associated with explosive eruptions |
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Definition
| ash fall, pyroclastic blasts and surges, lateral blasts. Mud flows and flooding. |
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Term
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Definition
| November 1985. Small eruption that produced ash-fall and pyroclastic flows which mixed with rock and water to create DEVASTATING MUDFLOWS. These fast travelling flows destroyed the towns of Amero and Chinchina, killing 25k. |
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Term
| Soufrière pyroclastic flow |
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Definition
| Collapse of the eruption column bc of loss of pressure. The collapse causes flows along sides of volcanoes. They tend to be cooler. |
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Term
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Definition
| Dome of viscous magma (rhyolite, dacite) block opening, creating pressure which builds up, causing violent blast down one side. Can possibly cause lateral blasts. |
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Definition
| Gravitational collapse of dacite/rhyolite magma in crater. (Merapi, Indonesia) |
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Definition
| 1982, surprise eruption bc it was not regarded as an active volcano. Over 2k were killed by pyroclastic surges, which also destroyed the nearby villages. |
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Term
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Definition
| Vesuvius erupted, 79AD, destroyed two towns of a population of 21k. Romans didn't know it was a volcano. Small explosions (vulcanian?) produced an ash cloud. Main event: plinian eruption column, ash fall, pyroclastic flows and surges destroy towns. |
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Term
| On what types of volcanoes do debris avalanches occur |
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Definition
| Stratovolcanoes and shield volcanoes. |
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Term
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Definition
| Long geological history, but major eruption in 1980. Initial mild vulcanian steam and ash then sustained plinian eruption producing: ash flow, debris avalanche, lateral blast, pyroclastic flow, mud flows. Subduction zone volcano! |
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