Term
| Where does the leading edge occur? |
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Definition
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Term
| Where does the trailing edge occur? |
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Definition
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Term
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Definition
| Long linear chains of volcanoes that lie on the leading edge of a lithospheric plate; they develop on 100 km from a trench |
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Term
| Continental-Margin Island Arc |
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Definition
| when a volcanic arc develops on the leading edge of continental lithosphere; Andes Mt. |
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Term
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Definition
| when a volcanic arc develops along the leading edge of oceanic lithosphere; Alaskan Peninsula |
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Term
| What are three types of volcanoes? |
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Definition
| Strato (Composite), shield, and Cinder Cones |
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Term
| Strato (Composite) volcanoes |
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Definition
| are most commonly found within island arcs but also occur in continental rift settings. it is also made up of different layers of pyroclastic material and solidified lava; steep |
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Term
| What is the material found in composite volcanoes made of? |
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Definition
| material that is intermediate (andesitic) in composition, but also mafic (basaltic) and silicic (rhyolitic) are additional volumetrically less significant components. |
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Term
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Definition
| large land forms with gentle slopes |
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Term
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Definition
| constructed of pyroclasts that are ejected and concentrated around a central vent; smaller than shield volcanoes |
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Term
| Mohorovicic discontinuity |
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Definition
| where the streams of magma encounter the boundry and their upward migrations is arrested |
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Term
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Definition
| (underplating) the accumulation of magma at the crust-mantle boundary |
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Term
| What forms the magma chambers? |
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Definition
| when magma breaks free from the Moho and rises higher into the crust ponding |
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Term
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Definition
| head or thermal anomalies that occur in intraplate settings, that is settings away from the boundaries of plates; Yellowstone and Hawaii |
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Term
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Definition
| without a significant loss of heat |
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Term
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Definition
| elongate basins (topographic depressions) produced by a stretching or pulling apart of the crust |
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Term
| What happens to magma produced in rifting? |
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Definition
1)effuses out of fissures (large open cracks) as so called flood basalts
2) builds large shield volcanoes erupting from a single vent
3) builds large stratovolcanoes as a result of violent eruptions alternating with effusive lava flows |
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Term
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Definition
| magma's internal resistance to flow when a shear stress is applied to it; measured in Pascal second; magma with a high viscosity has a high internal resistance to flow, while low viscosity is more fluid |
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Term
| During cooling, what happens to magma? |
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Definition
| at any given temperature, rhyolitic melts are always more viscous than are basaltic ones |
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Term
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Definition
| the ability to be dissolved within a liquid |
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Term
| Describe the solubility in magma. |
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Definition
| it is the "volatile phase" and is controlled by confining pressure exerted by the column of rock lying above the magma |
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Term
| The solubility of volatiles in magma rising upward through the crust __________ as it moves toward shallow near-surface depths. |
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Definition
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Term
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Definition
| at a certain critical relatively shallow depth it will become supersaturated with H2O and CO2 |
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Term
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Definition
| the pressure produced by H2O and CO2 gas separating from the magma at a given temp |
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Term
| First boiling (isothermal decompression) |
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Definition
| the exsolution of H2O and CO2 resulting in lowered confining pressure |
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Term
| Second boiling (retrograde boiling) |
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Definition
| increases in vapor pressure within the magma that causes it to rise to equal that of the confining pressure |
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Term
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Definition
| the general process of exsolution of volatiles from magma |
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Term
| If magma is degassed without an explosive eruption occurring, what will happen? |
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Definition
| it will effuse from the volcano as lava |
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Term
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Definition
| the pressure surface that forms when the volume of bubbles is about 75% of the total volume of the magma column |
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Term
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Definition
| the region of hot gas and fragmented pyroclastic materials lying above the fragmentation surface |
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Term
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Definition
| occurs in the lower part of the eruption column where it consists of pyroclastic material, some still plastic, and gases driven vertically upward through expansion |
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Term
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Definition
| comprises about 90% of the eruption column and occurs where the density of the eruption column becomes less than that of the atmosphere |
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Term
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Definition
| downwind plume that occurs at the top of the eruption column |
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Term
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Definition
| material that rains down on the land surface blanketing it |
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Term
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Definition
| a rock deprived from an air-fall deposit composed mostly of ash; one composed of lapilli would be called an "air-fall lapillistone" |
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Term
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Definition
| mixtures of hot gas, tephra and rock fragments |
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Term
| Volcanic Explosivity Index |
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Definition
| index based on the volume of material erupted, the height of the eruption column, and the duration of the eruption; ranges from 0-8; Hawaiian eruptions rank 0's and are least explosive |
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Term
| Rank the eruptions from least destructive to most. |
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Definition
| Hawaiian, Strombolian, Volcanian, Plinian, Ultraplinian |
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