Volcanoes. Formed at Plate Boundaries Ring of Fire!
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Transcript of Volcanoes. Formed at Plate Boundaries Ring of Fire!
Types of lava and eruptions
• Mafic Lava: Rich in magnesium and poor in silica. Erupts generally quietly and is not viscous (flows easily. Dark color. (Example: Mauna Loa in Hawaii).
• Felsic Lava: Rich in silica and poor in magnesium. Erupts violently with pyroclastic flows and ash. Light color. Very viscous. (Example: Mt. Vesuvius and Mt. St. Helens.)
Shield Volcano
• Broad with gently sloping sides.
• Quiet eruptions with mafic lava
• Usually the lava hardens into Basalt, which makes up the ocean floor.
• Largest volcano• Example: Mauna Loa in
Hawaii
Cinder Cone Volcano
• Very steep slopes• More felsic and
explosive eruptions.• The cinders of volcanic
rock (scoria, pumice) are deposited to form a cone.
• Example: Mauna Kia in Hawaii
Composite Volcano/Stratovolcano
• Tall and steep• Alternating layers of lava
flows and pyroclastic material (ash).
• Mostly explosive eruptions due to felsic magma though some quiet lava flows.
• Very Viscous lava • Examples: Mt. Fuji in Japan
and Mt. St. Helens in Washington State.
Volcanoes from Rifting Plates
• When plates diverge, magma can rise up and form a rift-volcano.
• Examples: Mid-Atlantic Ridge and African Rift Valley.