Term
| can a volcano come from a fissure in a hill |
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Definition
| yes. volcanoes usually have craters, erupt lava or ash and are a hill or mountain |
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Term
| 4 main types of volcanoes |
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Definition
1. shield- usually mafic magma, gentle slopes
2. composite- interlayered lava flows, pyroclastic deposits, mudflows
3. Volcanic dome- viscous and felsic magma
4. Scoria cone- coneshaped hills several hundred meters high. Balsatic in competition. can form next to composite or shield volcanoes |
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Term
| Describe four ways that magma erupts |
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Definition
1. Pyroclastic eruptions- ash collapses down the side of the volcano as a dense substance.
2. Eruption Column- tephra is shot into the air and comes down as solidified and cooled pieces of rock
3. Lava dome- forms from the eruption of highly viscous lava. high silica content.
4. Lava fountain- accompanies basaltic volcanoes |
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Term
| How is gas dissolved in magma and how does it behave at different depths in magma |
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Definition
| Think of opening a soda-- the pressure is always there but only evident when it is opened (erupts). |
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Term
| How does viscosity influence how explosive an eruption is? |
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Definition
More viscous=bigger eruptions
Less viscous=smaller eruptions |
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Term
| how do shield volcanoes form |
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Definition
| a succession of basaltic lava flows and lesser amounts of scoria and ash |
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Term
| how do shield volcanoes erupt |
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Definition
| non explosive because the magma isn't as viscous. |
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Term
| what are composite volcanoes |
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Definition
| constructed of interlayered lava flows, pyroclastic flows, tephra falls and volcano related mud flows. lava essentially comes out of two cones instead of one. mt vesuvius was one |
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Term
| how do volcanic domes form |
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Definition
| the domes form when viscous lava mounds up above and around a vent. |
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Term
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Definition
| A caldera is a volcanic feature formed by the collapse of a volcano into itself, making it a large, special form of volcanic crater. A caldera collapse is usually triggered by the emptying of the magma chamber beneath the volcano, as the result of a large volcanic eruption. Yellowstone is one. |
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Term
| what is mafic and felsic magma |
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Definition
| Mafic lava, before cooling, has a low viscosity, in comparison to felsic lava, due to the lower silica content in mafic magma. Water and other volatiles can more easily and gradually escape from mafic lava, so eruptions of volcanoes made of mafic lavas are less explosively violent than felsic-lava eruptions. |
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Term
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Definition
Stress is simply the force per unit area that is deforming the rocks, whether that is compression, extension, or shear.
Confining pressure: same amount of stress from all directions
Differential pressure: different amounts of stresses from different directions
rocks respond to stress w/ displacement, rotation, and deformation.
stress= force/area
force= mass*acceleration |
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Term
| what are joints and faults |
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Definition
joint: crack where rock breaks but keeps moving
fault:crack where rock has slipped some distance |
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Term
| what are strikes and dips? |
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Definition
strikes: horizontal line of a surface (if you fill an area up with water)
dips: inclination of a surface |
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Term
| 3 different types of faults |
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Definition
1. normal fault
2. reverse/thrust fault
3. strike-slip fault-2 sides move horizontally relative to eachother |
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Term
| for how temperature affects rocks look at the diagram in ch8 slide 12 |
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Definition
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Term
| what are folds and the 3 different kinds |
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Definition
one or a stack of originally flat, level surfaces, such as sedimentary strata, are bent or curved as a result of pressure and high temperature. The basic cause is likely to be some aspect of plate tectonics. limbs are the 2 sides of the fold and the hinge is the top.
1. anticline- a ridge-shaped fold of stratified rock in which the strata slope downward from the crest.
2. monocline- a bend in rock strata that are otherwise uniformly dipping or horizontal.
3. syncline-a trough or fold of stratified rock in which the strata slope upward from the axis. |
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Term
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Definition
| a sudden and violent shaking of the ground, sometimes causing great destruction, as a result of movements within the earth's crust or volcanic action. |
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Term
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Definition
| faults (normal, strikeslip, reverse/thrust) when rocks one opposite sides of faults slip past eachother abruptly, the movement generates seismic waves. reverse faults typically produce the largest earthquakes |
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Term
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Definition
| the underground focus point of an earthquake. |
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Term
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Definition
| the point on the earth's surface vertically above the focus of an earthquake. |
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Term
| how are earthquakes related to subduction zones? |
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Definition
| a subduction zone, where an oceanic plate underthrusts beneath another oceanic place or a continental plate, undergoes compression and shearing along the plate boundary. it can produce very large earthquakes. |
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Term
| explain what a seismogram does |
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Definition
| records seismic waves. p waves, s waves (cant travel thru liquid), surface waves in that order |
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Term
| give details on fine grained rocks |
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Definition
| rapid cooling at shallow depth. extrusive, finely crystalline w/ vesicles |
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Term
| give details on coarse grained rocks |
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Definition
| slower cooling at deeper depth. intrusive, coarsely crystalline |
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Term
| how could changing temperature cause melting |
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Definition
solid: pressure holds lattice together
lqiuid: increasing temp vibrates atoms and can break bonds |
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