Transcript Volcanoes
VOLCANOES THESE NOTES GO ON P. 11 OF YOUR INB!!! VOLCANIC SETTINGS (PLATE BOUNDARIES) CONTINENTAL divergence OceanContinent Convergence Ocean Divergence Ocean-Ocean Convergence Major Volcanoes Around the World “RING OF FIRE”:Area surrounding the pacific plate where the most volcanoes & earthquakes occur PLATE TECTONICS AND MAGMA GENERATION PARAMETERS OF VOLCANISM Viscosity Chemistry of Magma Gases within the magma Water content of magma VOLCANIC ACTIVITY Active Volcanoes: recent eruptions, active magma source Mt. Dormant Volcanoes: no recent eruptions, but still has an active source of magma Mt. Etna, Italy St. Helens, USA Extinct Volcanoes: no recent eruptions, no source of magma Northwestern Hawaiian Islands TERMS TO KNOW: Viscosity- the resistance of lava to flow • Ex: The more viscous the lava, the thicker and stickier the material & the harder it is to flow (honey vs. water) • depends on the amount of silica •the type of crust being melted determines the amount of silica! TERMS TO KNOW: Caldera: large crater shaped basin that forms when the top of a volcano collapses FORMATION OF CRATER LAKE TERMS TO KNOW: Hot Spot- random upwelling of magma NOT associated with convection in the mantle create a special type of volcanism not associated with plate boundaries Ex: Hawaii, Yellowstone & Iceland Kaui Oahu Molokai Lanai Maui Hawaii TECTONIC SETTINGS AND VOLCANIC ACTIVITY 3 TYPES OF VOLCANIC CONES: 1. Cinder Cones: explosive eruptions, small but steep slopes, pyroclastics Cinder Cone VOLCANO TYPES 3 TYPES OF VOLCANIC CONES: 2. Shield: non-explosive eruptions, fluid basaltic lava, gentle broad slopes Volcano Types 3 TYPES OF VOLCANIC CONES: 3. Composite Cones/Stratovolcanoes: alternating between lava and pyroclastics, explosive and non-explosive eruptions, very steep/tall VOLCANO TYPES Volcanism at different plate boundaries MID-OCEAN RIDGES & OCEANIC HOT SPOTS Effusive Eruption (non-violent): low viscosity, flows easily, gases escape easily Magma Type: mafic (dark, dense seafloor) Volcano Type: Shield Volcanoes Lava Type: Pillow http://www.youtube.com/watch?v=DdIUuUY0L9c BASALTIC LAVA TYPES Pillow Basalts (underwater) http://www.youtube.com/watch?v=DdIUuUY0L9c AA lava- jagged lava Pahoehoe- ropey, smooth lava SUBDUCTION BOUNDARIES Mostly Explosive Eruption (violent): high viscosity, does not flow easily, gases trapped, hard to predict explosions Magma Type: felsic & mafic Volcano Type: Composite Cone (Stratovolcanoes) & cinder cones Other Features: gas flows, calderas, aerial bombs PYROCLASTIC FLOWS http://www.youtube.com/watch?v=-H_HZVY1tT4 Mt. St. Helens Eruption http://www.youtube.com/watch?v=WxlRpuTed6g Pyroclastic Flow searing superheated gas and volcanic ash & dust; very fast Also called “Nuee Ardente” DEBRIS AVALANCHE AND ERUPTION OF MOUNT ST. HELENS, WASHINGTON CONTINENTAL DIVERGENT BOUNDARY & CONTINENTAL HOT SPOTS Explosive Eruption (violent): high viscosity, does not flow easily, gases trapped, hard to predict explosions (always explosive!) Magma Type: felsic or rhyolitic Volcano Type: Composite Cone (Stratovolcanoes), cinder cones, dome complexes Other Features: gas flows, calderas, aerial bombs, pyroclastic flows Magma and Erupted Materials Basaltic Magma Andesitic Magma Rhyolitic Magma Silica Content Least (~50%) Intermediate (~60%) Most (~70%) Gas Content Least Intermediate Most Viscosity Least viscous Intermediate Most viscous Type of Eruption Rarely explosive Sometimes explosive Usually explosive Melting Temp. Highest Intermediate Lowest Rifts, oceanic hot spots Subduction boundaries Continental hot spots Location VOLCANO CARICATURES Draw an exaggerated, cartoon form of a type of volcano Cinder Shield (Dome) Composite Write a 5-6 sentence summary about it’s “personality.” Must include type of eruption, type of lava, size/shape, and location.