Shield Volcanoes Quiet eruptions of basaltic lava spread
Shield Volcanoes �Quiet eruptions of basaltic lava spread out in flat layers. �The buildup of these layers forms a broad volcano with gently sloping sides called a shield volcano. �The Hawaiian Islands are examples of shield volcanoes.
Cinder Cone Volcanoes �Explosive eruptions throw lava and rock high into the air. �Bits of rock or solidified lava dropped from the air are called tephra
Cinder Cone Volcanoes �Tephra varies in size from volcanic ash, to cinders, to larger rocks called bombs and blocks. �When tephra falls to the ground, it forms a steepsided, loosely packed cinder cone volcano �Paricutin- Video
Composite Volcanoes �Some volcanic eruptions can vary between quiet and violent, depending on the amount of trapped gases and how rich in silica the magma is. �An explosive period can release gas and ash, forming a tephra layer. �Then, the eruption can switch to a quieter period, erupting lava over the top of the tephra layer.
Composite Volcano �When this cycle of lava and tephra is repeated over and over in alternating layers, a composite volcano is formed.
Calderas �Sometimes after an eruption, the top of a volcano can collapse. �This produces a large depression called a caldera. �Eventually, the processes of weathering and erosion wear down rock at the surface, exposing features like batholiths, dikes, and sills.
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