VOLCANISM

VOLCANISM•Is the phenomenon of eruption of molten rock (magma) onto the surface of the earth or a solid surface planet or moon, where lava, pyroclastics and volcanic gases erupt through a break in the surface called a vent.

VOLCANIC PROCESSESS•Magma

▫From the mantle or lower crust rises through its crust to the surface.

▫If the magma reaches the surface, its behavior depends on the viscosity of the molten constituent rock.

VISCOSITY•Viscous ( thick )▫Magma produces volcanoes characterized by explosive eruptions

Viscous ( thick )

VISCOSITY•Non – Viscous ( runny ) ▫magma produce volcanoes characterized by effusive eruptions pouring large amounts of lava onto the surface.

NON – VISCOUS ( RUNNY )

ASPECTS OF VOLCANISM

AREAS OF VOLCANISMSub-ducting

Boundaries Plate Sub-ducts

below surface into mantle.

SUB-DUCTING BOUNDARIES

Oceanic-Oceanic Volcanoes form near boundary

OCEANIC-OCEANIC/SUDUCTING

Mid Ocean Ridges Eruptions occur where plates are diverging.

MID OCEAN RIDGES

▫Hot Spots remain stationary while plates move above

Hot Spots

HOT SPOTS

VOLCANOES▫Are placed where magma reaches the earth’s surface

▫The type of volcanoes depends on the location of the eruption and consistency of the magma

TYPE OF VOLCANOES▫Shield Cone

Has a low rounded profile

Gentle slopes of 2-10 degrees

SHIELD VOLCANO

TYPE OF VOLCANOES▫ Composite Volcano

(Strato Volcano) Both pyroclastic layers

and lava flows Steep sided near summit

with decreasing slope.

STRATOVOLCANO / COMPOSITE VOLCANO

TYPE OF VOLCANOESCinder ConePyroclastic Material (Fragmented material that has been explosively ejected)

Ash and debris accumulates around the vent

Small steep sided cones

CINDER CONE VOLCANO

VOLCANISMPREPARED BY:

DAISYRELLE C. COMIDA