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by lilypop96
Last updated 10 years ago

Earth Sciences

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Divergent Boundaries

Most divergent plate boundaries are at the bottom of the oceans, therefore most volcanic activity is submarine, forming new seafloor.

Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. In this case, the oceanic plate subducts, or submerges under the continental plate forming a deep ocean trench just offshore. Water released from the subducting plate lowers the melting temperature of the overlying mantle wedge, creating magma. This magma tends to be very viscous due to its high silica content, so often does not reach the surface and cools at depth. When it does reach the surface, a volcano is formed.

Convergent Boundaries

Shield Volcanoes

Lava Domes

Lava domes are built by slow eruptions of highly viscous lavas

are formed by the eruption of low-viscosity lava that can flow a great distance from a vent, but not generally explode catastrophically.

Mud volcanoes

are formations created by geo-excreted liquids and gases, although there are several different processes which may cause such activity

Submarine Volcanoes

Submarine volcanoes are common features on the ocean floor. Some are active and, in shallow water, disclose their presence by blasting steam and rocky debris high above the surface of the sea.

Pillow lava is a common eruptive product of submarine volcanoes.

Subglacial Volcanoes

Subglacial volcanoes develop underneath icecaps. They are made up of flat lava which flows at the top of extensive pillow lavas and palagonite. When the icecap melts, the lavas on the top collapse, leaving a flat-topped mountain. These volcanoes are also called table mountains, tuyas

Volcano Diagram



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