EOSC 114 Notes for Exam - Volcanoes

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Earth and Ocean Sciences
EOSC 114
Leah May Ver

EOSC 114: Volcanoes Learning Goals 1. Explain what magma density and magma Density: less mass/volume so magma (melted viscosity are. rock) rises above solid rock. Viscosity: how runny, fluid magma is; low viscosity (runny, flowing) will rise through crust; dependant on SiO c2ntent and temperature more SiO , higher viscosity 2 (stronger bond = more solid) - For magma to rise through crust, it must have lower density than crust, low viscosity, and hot enough to stay liquid 2. List the different categories of volcanic - Intrusive rocksmagma that cools slowly rocks and explain the differences between the underground, crystals visible magmas they came from. - Extrusive rocks  magma cools quickly on surface, crystals too small to see -Mafic magma: low SiO co2tent, low viscosity, less explosive (ex. form basalt rocks) -Felsic magma: high SiO content, high 2 viscosity, more explosive (ex. form rhyolite rocks) BasaltAndesiteRhyolite 3. Explain why some magmas erupt Depends on gas content and viscosity explosively (as pyroclastic material) and some Lava: low gas content, low viscosity, flows as magmas erupt effusively (as lava). pahoehoe or a’a (see 4) Volcanic glass: magma cools quickly before crystallizationobsidian if solid or pumice if bubbles Pyroclastic material: high gas content, high viscosity more explosive 4. Explain the differences between pahoehoe Pahoehoe: smooth, rope-like texture and a'a lavas A’a: rough, painful surface 5. Describe the different types of volcanic eruptions and how they are related to magma properties. 6. Describe the morphology, dominant rock Mafic volcanoes: type and typical eruption style of the different -Shield volcano flat, broad (100s of km wide) types of volcanoes. basalt lava flows; low explosivity -Scoria/Cinder conessmall, volcanic vent made of pyroclastic material, found around other volcanoes (ie. shield) or on own; medium-high volatility Intermediate to Felsic volcanoes: -Composite/Stratovolcanoesconical shape with steep slope, made of layers of lava and pyroclastic material; medium-high volatility (bigger than cinder cones so more dangerous) -Lava domelava flow collection over vent, keeps expanding with explosions; medium volatility when erupts EOSC 114: Volcanoes Learning Goals Felsic volcanoes: - Calderasdepressions in crust formed when explosion causes collapse Don’t confuse with crater, which is just a depression when eruption occurs without collapse 7. Explain what lava flows, fire fountains, lava -Lava flow: melted magma rises through crust bombs, and volcanic ash are and how they and flows out of volcano slowly form. -Fire fountain: basaltic lava with lots of gas erupts (small) and as it falls, cools as lava -Lava bombs: large chunks of pyroclastic material -Volcanic ash 8. Describe the particular hazards associated -Lava flow: destroy infrastructure with lava flows, fire fountaining, lava bombs, -Fire fountain: very hot and ash fall. -Lava bomb:can kill people, damage things -Ash fall:can suffocate people, bury cities, stop planes/car engines, block solar
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