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75 Cards in this Set
- Front
- Back
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What is pyroclastic materials or tephra?
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Fragmented materials made of ash and "bombs"
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What is Fumorontic?
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Emits only gas
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What is extinct volcano?
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No longer active volcano
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What is dormant volcano?
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Potentially active but not erupting at the present
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How can we classify volcanos?
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By their lava type, eruption style, and landform
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What are the primary factors that determine the lava type?
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Silica content, viscosity, gas content.
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What is viscosity?
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The thickness of the liquid. The higher the viscosity the less it flows and the lower the viscosity the easier it flows.
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Why is Silica important?
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Earth's crust is dominated by silica. In a volcano silica content can range from 50% to 75%, primary factor that controls volcano behavior.
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How are viscosity and Silica content related?
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The higher the silica content the higher the viscosity.
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What is effusive eruption style?
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lava pours out of volcano and flows down hill, low viscosity.
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What is explosive eruption style?
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When pressure builds and lava explodes out, high viscosity.
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What is the characteristics of gas content in volcanoes?
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Ranges from .5% to 7.5%, more gas more pressure to make more explosive. High silica, high viscosity and high gas content produce explosive volcanoes.
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What volcano type has low gas content and low viscosity/silica?
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Shield volcano
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What volcano type has medium gas content with low viscosity/silica
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Spattering Cynder Cone
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What volcano landform has medium gas content and medium viscosity/silica content
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Strata or Composite Volcano
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What volcano landform has high gas content and high viscosity/silica content?
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Caldera
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What volcano landform has low gas and high viscosity/silica?
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Volcanic dome
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What is the definition of a rock?
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Coherent naturally occuring solid, consisting of an aggregate of minerals or a mass of glass
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What is the definition of a mineral?
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Homogeneous, naturally occuring solid inorganic substance with a definable chemical composition and an internal structure.
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How can we classify volcanic rock types?
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Magma Composition, Volcanic Rock texture, volcanic rock mineral assemblage, pyroclastic rock types.
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What chemicals are present in magma composition?
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Si, Al, Fe, Ca, Mg, Na, K, H, O
Silica, Alluminum, Iron, Calcium, Magnesium, Sodium, Potassium, Hydrogen, Oxygen. |
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What are the chemical compositions of Basalt?
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low silica - 45 - 55%
higher Iron/Magnesium and Calcium content Lower Sodium and Potassium |
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What are the chemical compositions of Andesite
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medium silica - 55 - 65%
medium Iron/Magnesium and Calcium content medium Sodium and Potassium |
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What are the chemical compositions of Rhyolite?
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high silica - 65 - 75%
low Iron/Magnesium and Calcium content higher Sodium and Potassium |
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What classifies materials as mafic or felsic?
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Mafic is rich in Fe/Mg and Dark in color - Basalf
Felsic is Fe/MG depleted and light in color - Rhyolite |
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What is the relationship of Silica and Light or dark material?
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High Silica results in lighter color than low silica which results in dark color.
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Intrusive vs. Extrusive
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Intrusive or Plutonic is
1. formed below the surface 2. Slow cooling 3. Large crystals Extrustive or volcanic 1. On the surface 2. Fast/very fast cooling 3. Small crystals or glass |
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What are the different ingeneous rock textures?
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Aphanitic
Phaneritic Porphyritic Glassy Vesicular Pumiceous |
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What are the gas/viscosity/explos/temp of Basalt?
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Gas - 1%
Viscosity - low Explosicity - Effusive Temperature - 1250 C |
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What are the gas/viscosity/explos/temp of Rhyolite?
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Gas - 5%
Viscosity - high Explosicity - Explosive Temperature - 800 C |
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What are the properties of Andesite?
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In the middle of Basalt and Ryolite. Just now that from Basalt going to Rhyolite the gas content increases along with viscosity and explosiveness but temperature goes down
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What is pyroclastic rock?
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Fragments of rock that come out of volcano classified by size and texture
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What is a tephra/pyroclastic material that is greater than 64 mm and the pyroclastic rock name?
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A Bomb
Pyroclastic name: Agglomerate |
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What is a tephra/pyroclastic material that is between 2 and 64 mm and the pyroclastic rock name?
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Lapilli
Pyroclastic rock: Lapillituff |
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What is a tephra/pyroclastic material that is les than 2 mm and the pyroclastic rock name?
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Ash
Pyroclastic rock: Ash tuff |
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What is an Obsidian rock?
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100% Glassy
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Name the crystal size, cooling rate, and intrusive or extrusive of the rock texture:
Aphanitic |
Fine crystals, Fast cooling, Extrusive
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Name the crystal size, cooling rate, and intrusive or extrusive of the rock texture:
Phaneritic |
Coarse crystals, slow cooling, intrusive
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Name the crystal size, cooling rate, and intrusive or extrusive of the rock texture:
Porphyritic |
Coarse and fine crystals, slow and fast cooling, extrusive
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Name the crystal size, cooling rate, and intrusive or extrusive of the rock texture:
Pumiceous |
None (frothy) crystals, very fast cooling, and extrusive
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Name the crystal size, cooling rate, and intrusive or extrusive of the rock texture:
Glassy |
No crystals, very fast, extrusive
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Name an intrusive and extrusive "dark" rock
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Extrusive: Basalt
Intrusive: Gabbro |
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Name an intrusive and extrusive "intermediate" rock
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Extrusive: Andesite
Intrusive: Diorite |
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Name an intrusive and extrusive "light" rock
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Extrusive: Rhyolite
Intrusive: Granite |
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What plate boundary areas can volcanoes occur?
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Subduction zones, Divergent plate boundaries, Intrapalate.
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What plate boundaries do volcanoes NOT form in?
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Continent to Continent collision, and transform boundaries
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What are the 3 ways to lower the melting point of a rock?
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1. Decrease pressure
2. Raise Temperature 3. Add "contaminant" - small quantity of foreign material to change chemical composition |
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In a subduction zone, which way to change melting point occurs?
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Add contaminant
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In a divergent plate boundary ex. Mid Ocean Ridge, which way to change melting point occurs?
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Decrease in pressure
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In an Intrapalate area, which way to change melting point occurs?
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Increase in temperature
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What is the primary characteristic that controls volcano type?
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Viscosity
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What is the primary characteristic that control viscosity?
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Silica
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What is fractional crystalization?
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forming of crystals in a magma that changes its chemical composition that makes it richer in some materials and depleted in others.
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During fractional crystalization what is the chemical composition of the crystals being formed?
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low in silica, high in Fe, Mg, Ca,
Low in Na, K |
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During fractional crystalization what is the chemical composition of the leftover magma after the crystals have formed?
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Higher in Silica
Lower in Fe, Mg Higher in Na, K Also viscosity, water content, and Explosiveness all INCREASE |
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What is assimilation?
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dissolution of chemical components of surrounding rock
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What is magma mixing?
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New magma comes into a magma chamber and mixes together forming a new composition
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What causes the buoyant ascent of magma?
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1. Melting is an expansion of volume
2. Decrease in density 3. Upward flow due to gravity. Also when the magma find neutral buyouncy it stops and loses heat and fractional crystalization occurs. |
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What factors control viscosity?
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Higher silica content = higher viscosity
Higher temperature = lower viscosity, because the temp raised speeds up molecules |
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What are the different gases found in volcanoes?
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CO2, SO2, H2O, H2S
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What is exsolution?
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When gas comes out of solution in magma and creates bubbles, as bubbles rise they increase in size thus volume of gas increases and leads to fragmentation
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What is the gas thrust area?
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When pressure is pushing out of the volcano
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What is the convective thrust area?
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When the hot air rising into the atmosphere
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What is the umbrella region?
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Where the gas finds area of neutral density and wind pushes it off to one side
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What are the volcanic hazards?
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Ash fall
Pyroclastic fall Lava Flow Lahar Landslide/Avalanche Tsunami Gas and others (Lateral blast, flooding, wildfires) |
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What are the characteristics of an Ash Fall?
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* Covers all topography
* Distances to 100+ km * Wind dispersal of ash * Coarse tephra close to vent |
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What are the characteristics of an Pyroclastic Flow?
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* Affects low-lying areas
* Distances to ~20 km * Affects areas close to vent |
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What are the characteristics of an Lava Flow?
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* Vent area + low-lying areas
* Distances to 10 km (silicic magmas) * Greater distances for more fluid magmas |
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What are the characteristics of an Lahar?
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* Confined to river valleys
* Distances to 70+ km * Source area of ash, poorly consolidated rock |
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What are the characteristics of a landslide/avalanche?
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* High-relief areas near volcano
* Ice cap |
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What are the characteristics of a tsunami?
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* Low-lying coastal areas near volcano
* Source area: submarine eruptions/landslides |
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What are the characteristics of a Gas Hazard?
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* Areas close to summit vent
* Low-lying areas near lakes |
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What are the properties of a volcano in Fuji, Japan?
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Subduction Zone
High Viscosity High Gas Content High Silica Content Explosive eruptions Strato Volcano Rhyolite rock type |
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What are the properties of a volcano in Surtsey, Iceland?
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Divergent plate boundary
Low Viscosity Low Gas Content Low Silica content Effusive Eruption Shield Volcano Basaltic Rock |
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What are the properties of a volcano in Kilauea, Hawaii?
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Intrapalate hot spot, Low Viscosity, Low Gas Content, Low Silica, Effusive Eruption Style
Shield volcano Basaltic Rock |
