LOCATIONS OF VOLCANOES About 80 of volcanoes form

LOCATIONS OF VOLCANOES • About 80% of volcanoes form at convergent plate boundaries • About 20% of volcanos form at divergent plate boundaries. • Hotspots: Occurs when a mass of hotter than normal mantle material (mantle plume) rises toward the surface. (There have been 40 hotspots identified. ) Ring of Fire: The area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean.

MAGMA • All volcanos are fueled by magma • In order to create magma, you must have temperature, pressure, and water

MAGMA VS. LAVA Viscosity: resistance to flow

Viscosity: resistance to flow Viscous – thick, slow moving , typically cooler temperature Less Viscous – thin, fast moving, typically hotter temperature Viscosity depends on two factors: Temperature (the cooler it is, more viscosity. ) Composition (higher the silica content, more viscosity)

ANATOMY OF A VOLCANO • Neck: channels magma to crater • Vent: where magma reaches the surface neck – • Crater / Caldera: bowl shaped depression that forms around the vent • Magma Chamber: storage chamber for magma, feeds magma to vent or neck

TYPES OF VOLCANOES – SHIELD • Gently sloping sides, circular base • Formed by layer upon layer of basaltic lava • Nonexplosive Kohala, Hawaii

TYPES OF VOLCANOES – CINDER CONE • Steep sides, cone shape • Have water and silica content in magma • Ejected material piles up around vent Arizona

TYPES OF VOLCANOS – COMPOSITE / STRATOVOLCANO • Largest type • Larger amounts of silica, water and gas • Violent, explosive nature Mt. Fuji, Japan

VOLCANIC MATERIAL Lava Flow – flow of lava

VOLCANIC MATERIAL Lava Flow – flow of lava Pyroclastic Flow – mixture of clouds of gas, ash, and rock fragments (can travel up to 200 km/hr)

VOLCANIC MATERIAL Lava Flow – flow of lava Pyroclastic Flow – mixture of clouds of gas, ash, and rock fragments (can travel up to 200 km/hr) Ash Cloud – thin ash particles ejected into the atmosphere

1, 500 active volcanoes on earth

INTRUSIVE MAGMA FORMATIONS • The structures that result from the cooling and hardening of magma at depth are called plutons. • All plutons form beneath earths surface • Uplifting and erosion expose them

LOOKING GLASS ROCK, NC One of the largest masses of granite in the Eastern United States

TYPES OF IGNEOUS FORMATIONS • Laccoliths – viscous magma that has collected, and intruded close to the surface – Looks like a mushroom Batholi th

TYPES OF IGNEOUS FORMATIONS • Sills – forms when magma is intruded close to the surface – Looks like horizontal lava flows Batholi th

TYPES OF IGNEOUS FORMATIONS • Dikes – form when magma is injected into fractures – Cuts across preexisting rock layers Batholi th

TYPES OF IGNEOUS FORMATIONS • Batholiths – forms from cooled magma chambers – Largest intrusive formation Batholi th