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.
Calderas Yellowstone is an example of a caldera type eruption
Volcanoes from Rifting Plates When plates diverge, magma can rise up and form a rift-volcano. Examples: Mid-Atlantic Ridge and African Rift Valley.
Flood Basalts: Well that’s weird. 17-12 Million Years ago, miles long rifts in Washington and Oregon erupted huge flows of basalt. Called Flood Basalts. Geologists not really sure why it happened.