GLG 171 Week 6 Volcano Notes
GLG 171 Week 6 Volcano Notes GLG 171 - 003
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This 5 page Class Notes was uploaded by Hayley Notetaker on Thursday September 29, 2016. The Class Notes belongs to GLG 171 - 003 at Missouri State University taught by Dr. Kevin Mickus in Fall 2016. Since its upload, it has received 44 views. For similar materials see Environmental Biology in Biology at Missouri State University.
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Date Created: 09/29/16
GLG 171 – Volcano Notes Volcanoes - VENT: where magma and other volcanic products erupt onto the surface. - Some eruptions do not produce mountains but are still classified as volcanoes - Volcanoes are generally found at plate boundaries generally. 1)Mid Ocean Ridges 2)Subduction Zones 3)Hot Spots (Stationary point in tectonic plate where magma rises up from the asthenosphere) Types of Volcanoes - Shield - Composite (Strato) Volcano - Cinder Cone - Fissure Eruption What controls the shape of volcanoes? - Viscosity of magma - Tectonic setting What controls the viscosity? - Silica (SO2) content - Higher SO2 -> higher viscosity - Higher viscosity -> Harder to flow - Felsic magma -> Rhyolite - Less SO2 -> Low viscosity -> magma will flow easier - Mafic magma -> Basalt Temperature - Hotter magma -> less viscosity - Colder magma -> high viscosity Types – in detail A)Shield - Made of basalt layers - Flow will cover a larger distance - Volcanoes usually cover large areas - Shallower slopes - Tephra (pyroclastic material) may be at top - Not explosive - Found at hot spots and mid ocean ridges B)Composite (Strato) - Made of layers of pyroclastic material - More viscous - Flow will only cover a short distance - Steeper slopes - Usually erupt violently - Found at subduction zone (Cascades, Andes) - Smaller surface area than Shield volcanoes C)Cinder Cones - Small, Steep - Mainly pyroclastic - Viscous material mostly - Numerous volcanoes - Occur in all tectonic environments - Can last a few years D)Fissure Eruption 2 - Occur in linear cracks in the crust where lava seeps out - Always basaltic magma - Flows easily - Layers of flat basalt - Found at Mid Ocean Ridges and hot spots Other Features: 1)Crater – bowl shaped depression on top of volcano where eruption occurs. 2)Domes- usually a high silica content material that flows into the crater after the large eruption. 3)Calderas – a large crater that forms after a large eruption. - Occurs in strato volcanoes - Crater forms when the top of the volcano is gone, magma chamber is emptied or the volcano collapses into the old chamber Volcanic Hazards 1)Lava Flow - Hot - Burns everything in path – usually only shield volcanoes - Lots of property damage 2)Pyroclastic Eruptions - Strato volcanoes - Airborne material - Ash and lava bombs - Volcanic material covers everything - Volcanic ash has glass that can be hazardous and uncomfortable to breathe 3 A)Airborne - Bad for air travel - Ash will stay in air for years - Lowers Earth temperature - Dangerous to breathe B)Comes to Ground - Ash can be very heavy - Structural damage - Slightly acidic -> acid rains eventually - Damages to water supply - Kills plants 3)Lahars - Mix of water and ash flows down valley - Density of concrete - Destroys all 4)Pyroclastic Flows – Nuees Ardentos - Gas/Ash – denser than air, flows downward 5)Toxic Gases - H2O, CO2, Cl, F, SO2**, NO2 **- most important - CO2 is toxic - Denser than air, colorless, odorless – suffocation Predicting Eruptions 1)Seismology - Where the magma is located (depth, width, thickness – how much) 2)Ground Deformation - Tilt meters – tells angle of slope (magma pushes the ground upwards) - GPS – see movement up/down of ground 3)Gas Output - Big increase -> magma close to surface - Looking for amount of SO2 4)Geological History 4 - Looks at rocks from previous eruptions for information about patterns, types of explosions 5
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