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57 Cards in this Set
- Front
- Back
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Where does most volcanism take place?
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-On edges of techtonic plates and less often, over hot spots.
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What is volcanic activity like over subduction zones?
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-Explosive and bad earthquakes, rhyolitic magma.
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What is an example of studbuction zone volcanoes?
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-Mt. St. Helens and Mt. Fuji
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What is volcanic activity like over spreading centers?
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-Voluminous magma and peaceful eruptions.
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What is an example of spreading center volcanoes?
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-Iceland. Oceanic volcanoes.
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Where does most magma come from?
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-rifting or divergent boundaries, below sea level.
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What are the three igneous rock types important to volcanism?
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-andesite, basalt, and granite.
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What is basalt?
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heavier, iron bearing mafic (dark colored) igneous rock. What the ocean floor is made of.
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What is granite?
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-felsic (light colored) rock with large coarse crystals.
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What does the presence of water do to the melting point of rock?
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-water lowers the melting point of rock.
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How can you identify the age of islands over hotspots?
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-age is from youngest to oldest in the direction of plate movement.
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How does the amount of silica affect volcanoes?
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-the more rich in silica, the more explosive the volcano.
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What are plutonic rocks?
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-rocks that re cooled slowly deep inside Earth, large crystals. Gabbro, diorite, and granite.
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What are volcanic rocks?
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-rocks that explode out the surface and are quickly cooled, small crystals. Basalt, andesite, and thyorite.
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What is viscosity?
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-resistance to flow. The lower the viscosity, the more fluid like.
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How does viscosity change?
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-higher temp lowers it. SiO2 increases it by creating sheets with more difficult bonds to break, increase mineral content of magma, dissolved gas (like pop)
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What’s the difference between Basalt, Andesite, and Rhyolite?
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-Basalt is peaceful has a low viscosity and dark color. Rhyolite is explosive, has high viscosity and a light color. Andesite is in between these too.
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What is aa flow?
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-lava that’s low viscosity, non-explosive, chunky, i.e. Kilauea, Hawaii
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What is a pyroclatic flow?
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-high viscosity lava, gas escapes by explosive. Ahs and debris, ie. Mt. Pelee in the West Indies.
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Why does the majority of magma easily pour from spreading centers?
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-less SiO2 , higher temp, less crust to go through, more volatile and gassy.
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Why does the magma above subduction zones explode violently?
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Subducting plate brings water down with it, the water lowers the temp for melting rock. The magma temp decreases while SiO2, water, and viscosity increase causinga more violent explosion.
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How is magma generated?
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Lowering pressure on it, raising temperature, and increasing water content.
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What is decompression melting?
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The melting of solid, hot rock as it rises from the mantle.
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What are the differences between volcanic materials?
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Lava (aa, pahoehoe, pillow) are non explosive. Pyroclastic and glass are explosive.
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What are the different volcano types and where are they found?
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Shield
Scoria/Cinder cones Flood basalts Stratovolcanoes/ composite. |
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What are shield volcanoes?
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Spreading centers, low lying thin layers, basalt, i.e. Hawaii
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What are Scoria/Cinder cones?
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Spreading centers, short and steep.
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What are Flood basalts?
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Cracks in the earths surface, layers of basalt.
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What are Stratovolcanoes/ composite?
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Convergent boundaries, alternating layers of lava and ash.
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What are the 2 types of eruptions of shield volcanoes?
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Icelandic and Hawaiian.
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What are the largerst volcanic events?
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flood basalts where melted basalt pours onto Earth's surface thorugh cracks in the surface.
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What type of eruptions to scoria cones have?
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strombolian eruption types
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What type of eruptions do lava cones have?
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lava domes are plugged from vulcanian blast and plinian eruptions.
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What type of eruptions do Caldera volcanoes have?
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caldera which is blowing off the top
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What are the 2 types of shield volcanoes?
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icelandic and hawaiian
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What are icelandic eruptions like?
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Pancake batter on a griddle, ex. Mauna Loa
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What are hawaiian eruptions like?
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after earthquakes create lava fountains, ex. Haleakala
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What is the order of stratovolcano eruption types?
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Vulcanian (throat clearing), Plinian, and Caldera (top blown off)
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What is a lahar?
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volcanic mudflow set off by rain mixing with ash and gases.
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What is the significance of Surtsey, Iceland?
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It helped confirm the theory of plate tectonics in the 60’s.
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Why is Surtsey getting smaller?
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Erosion and weathering, no longer on Mid-Atlantic Ridge, and no new material being added.
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What is the Cascade Mountain Range?
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- It’s the pathway of mountains containing active volcanoes like Mt. Reiner, Mt. St. Helens, Crater Lake, and Mt. Shasta.
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How do we know the age of an eruption?
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By using the radiocarbon dates of dead trees.
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What do we know about Mt. Shasta?
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The second tallest in the Cascade Range.
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What are the ways a volcano can kill you?
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- ash fall, acid rain, bombs, lava dome, collapse, pyroclastic flow, lahar, lava flow, debris avalanche, gases released, ground water polluted.
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What is a pyroclastic flow?
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- super hot, turbulent cloud of ash, gas, and air rolling toward you at high speed. First there is a dome collapse, overspilling of the crater rim, directed blast, and an eruption column collapse.
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What is a Nuee Ardente?
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On Mount Pele, a red hot avalanche of incandescent gases and glowing volcanic fragments. The mass moves as solid particles of magma suspended in gas.
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How is famine related to volcanoes?
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- Gases can slow the growth of grasses. Large areas of land can be covered by lava. Pyroclastic fallout can devastate crops. ie. Iceland and Tambora, Indonesia.
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What are 3 causes of slope failure?
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Steepening the slope by fault movements, removing support from low on the slope, and adding mass high on a slope as sediment deposition.
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What does clay look like?
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It has a book like structure, made of inherently weak material, same shape all the way around, thin on the sides.
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How does clay form?
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During chemical weathering under conditions of low pressure and temperature. Feldspar decomposes to clay and has similar chemical composition but he internal structure is different.
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How do clays have their strength lessened?
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The clay is formed in the soil zone where water strips way elements and leaves unfilled positions. Different elements and water are taken in and out, expanding and contracting the clay mineral.
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What does the polarity of water mean?
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Water is slightly negative on one side and slightly positive on the other.
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What does absorbed mean?
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Water is sucked up
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What does adsorbed mean?
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Water sticks to the surface.
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How does water weaken Earth materials?
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By decreasing the cohesion of rocks, subsurface erosion, and the pressure in pores of rocks and sediments.
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How is there a decrease in cohesion?
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the overlying materials compresses rocks into smaller volumes and when overlying rocks are uncovered by erosion the rocks expand. The expansion increases porosity.
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