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25 Cards in this Set
- Front
- Back
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What are the three volcanic settings? |
1. Mid ocean ridges 2. Hot spots 3. Subduction zones |
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What is the morphology, dominant magma type/igneous rock produced, and explosive vs. non explosive status of MID OCEAN RIDGES? |
Dominant magma type: BASALT MAGMA, forms BASALT Morphology: LONG LINEAR VOLCANIC RIDGES NON-EXPLOSIVE eruptions: due to low silica, low gas content of basalitc magma |
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What is the morphology, dominant magma type/igneous rock produced, and explosive vs. non explosive status of HOTSPOT VOLCANOES? Where do they form? |
Dominant magma type: BASALTIC MAGMA, solidifies to form BASALT Morphology: shield volcanos NON-EXPLOSIVE eruptions: due to low silica, low gas content of basaltic magma form over rising mantle plume |
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What is the morphology, dominant magma type/igneous rock produced, and explosive vs. non explosive status of SUBDUCTION ZONES? Where do they form? |
Dominant magma type: BASALTIC< ANDESITIC AND RHYOLITIC MAGMAS. FORM THOSE TYPES OF ROCKS. Morphology: STEEP SIDED COMPOSITE VOLCANO EXPLOSIVE eruptions: (high silica, high gas content in andesitic and rhyolitic magmas) form on the over-riding plate |
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What is larger, shield or composite cone/strato volcano? Mauna Loa vs. Mt Rainier? Which has a crater and which has a caldera? |
Shield is much larger. Shield has a caldera. |
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By what two means do we classify igneous rocks? |
1. Composition Malfic --> intermediate --> felsic 2. Place of Crystallization Leads to diference in grain size Extrusive (volcanic), fine grained Intrusive (plutonic), coarse grained |
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Rank the extrusive igneous rocks from mafic to felsic and name them. |
1. Basalt 2. Andesite 3. Rhyolite. |
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Rank the intrusive igneous rocks from mafic to felsic and name them. |
1. Gabbro. 2. Diorite. 3. Granite. |
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What types of minerals are in felisc and intermediate rock types? What types are in mafic? |
In felsic and intermediate, quartz --> feldspar. In Mafic, Pyroxene and Olivine. |
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What is magma viscosity a function of? Which magma composition will have the greatest viscosity? |
Silica content and temperature. Rhyolitic (felsic). Least will be Basaltic (mafic). |
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Water boiling point at sea level? In Denver? At Mauna Loa? Why? |
100, 96.8, 75.6. Beacuse air pressure is lower at higher altitudes. |
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What is the solidus? What is mantle rock? |
The point at which the mantle begins to melt. Periodite (olivine + pyroxene) |
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Describe the process of adiabatic or decomrpession melting beneath mid ocean ridges. |
Solid mantle is pulled up by plate spreading apart. Creates a void of space. Solid mantle rises to fill the void, crosses Solidus, begins melting and continues to rise because it's less dense. |
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How and why does melting happen above hotspots? |
Because the mantle rising in a hotspot is hotter than mantle beneath a mid ocean ridge, it begins melting deper, adn produces more total melt than melting beneath a mid ocean ridge. |
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Describe the melting process at subduction zones. |
The ADDITION OF WATER to mantle peridotite LOWERS THE MELTING TEMPERATURE OF PERIODOTITE, SO IT BEGINS TO MELT. Water then released form subducting lithosphere. |
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Crystallization of basaltic magma, start and end. |
Start: Mafic Magma. High Fe, low Si, low gases, low viscosity. End: Felsic magma: low Fe, high Si, high gases; high viscosity. |
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Reasons for explosive vs. non explosive. Give the types for each. |
Non explosive: constant replenishmetn with basaltic magma (low gas, low viscosity). Mid ocean ridges, hotspots e.g. Hawaii. Explosive: small amounts of basaltic magma crystallize to adesitic and rhyolitic magmas (high gas, high viscosity). Subduction Zones. |
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What are the common types of basatlic lava eruption structures? |
1. Pahoehoe (ropey lava) (means "well stirred") 2. Aa (spikey lava) (means "to burn") 3. Pillow lava (lobes -- form only underwater. |
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What are the common types of Andesitic and Rhyolitic eruption strucutres? |
Pyroclastic materials (ash, dust, house-sized ejected materials); pyro=fire clastic =fragment |
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What is an example fo a flood basalt? |
Columbia River Flood Basalts: reputed approx 17 million years ago; mile-thick lava. |
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Crystallization in crustal magma chamber, what are the three steps? |
A. A magma having a mafic (basalitc) composition erupts fluid basalitc lavas. B. Cooling of the magma body causes crystals of olivine, pyroxene, and calcium-rich plagioclase to form and settle out, or crystallize along the magma body's cool margins. C. The remaining melt will be enriched with silica, and should a subsequent eruption occur, the rocks generated will be more silica rich and closer to the felsic (granite) end of the compositional range thant he initial magma. |
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Caldera formation |
Surface puts pressure on partially emptied magma chamber. Resurgent dome can create island like Wizard Island in Crater Lake. |
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What is a pluton? What is a batholith? What is an example of each? |
Crystallized magma chamber. Many associated plutons. Half Dome; Sierra Nevadas. |
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What is a dike? What is a sill? |
Dike: near vertical tabular bodies. Sills: near horizontal tabular bodies. Used to house magma in plutonic structures. |
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How are plutons formed? |
1. Emplacement of magma and related igneous structures. 2. Crystallization of magma to form plutons. Erosion exposes some plutons. 3. Extensive uplift and erosion exposes batholith. |
