Volcanoes Chapter 9

Volcanic Settings (Plate Boundaries) Ocean-Continent Convergence Ocean-Ocean Convergence CONTINENTAL divergence Ocean Divergence

Major Volcanoes Around the World

“RING OF FIRE”:Area surrounding the pacific plate where the most volcanoes & earthquakes occur

Plate Tectonics and Magma Generation To view this animation, click “View” and then “Slide Show” on the top navigation bar.

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. Etna, Italy Dormant Volcanoes: no recent eruptions, but still has an active source of magma Mt. 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) the type of crust being melted, determines the amount of silica! the amount of silica in the magma determines the viscosity!

Terms to know: Caldera: large crater shaped basin that forms when the top of a volcano collapses

Formation of Crater Lake To view this animation, click “View” and then “Slide Show” on the top navigation bar.

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 Molokai Hawaii Oahu Lanai Maui

Tectonic Settings and Volcanic Activity To view this animation, click “View” and then “Slide Show” on the top navigation bar.

3 types of volcanic cones: Cinder Cones: explosive eruptions, small but steep slopes, pyroclastics Cinder Cone

Volcano Types To view this animation, click “View” and then “Slide Show” on the top navigation bar.

3 types of volcanic cones: Shield: non-explosive eruptions, fluid basaltic lava, gentle broad slopes

Volcano Types To view this animation, click “View” and then “Slide Show” on the top navigation bar.

3 types of volcanic cones: Composite Cones/Stratovolcanoes: alternating between lava and pyroclastics, explosive and non-explosive eruptions, very steep/tall

Volcano Types To view this animation, click “View” and then “Slide Show” on the top navigation bar.

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

C Basaltic Lava Types Pillow Basalts (underwater) AA lava- jagged lava 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

C 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 To view this animation, click “View” and then “Slide Show” on the top navigation bar.

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 Silica Content Melting Temp. Gas Content Viscosity Type of Eruption Location Least (~50%) Basaltic Magma Least Least viscous Rarely explosive Highest Rifts, oceanic hot spots Rhyolitic Magma Most (~70%) Most Most viscous Usually explosive Lowest Continental hot spots Andesitic Magma Intermediate (~60%) Intermediate Sometimes explosive Subduction boundaries

Volcano Caracitures 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.