Extrusive Volcanoes

Volcano?

A mountain or hill having a crater or vent through which lava, rocks, fragments, hot vapor and gas are or have been erupted from the earths surface

Two main types of lava

Viscous (acidic) and Basic

Differences between two types of lava

Viscous- High in silica, Resistant to flow, more explosive eruptions. Forms steep sided volcanoes

Basic-low in silica, Flows easily, less explosive eruptions. Forms gentle sloping Volcanoes

Types of Extrusive Volcanic features

Shield Volcanoes

Volcanic lava domes

Ash and cinder cone volcanoes

Composite Volcanoes

Basalt Plateau

Calderas

Visocous lava domes

Formed by viscous magma being erupted effusively unto the surface and then piling up around the vent. This lava is often thick

Ash cone volcanoes

When molten lava is thrown high in the air and it breaks up, cold and solidifies and turns into “ash”

Composite volcanoes

Some volcanoes produce both ash and lava eruptions, one after the other. The result is a composite volcano, with many layers of ash and lava built up over a long period of time.

Shield Volcanoes

Structures of this type are large, dome-shaped mountains built of lava flows. Their name derives from their similarity in shape to a warrior’s shield lying face up.

Classifications of volcanoes?

Active, Dormant, extinct

Basalt Plateaux

Basic lava flows to the surface over a wide area. The lava smothers hills and valleys of the existing landscape, producing a wide flat plateau.

Two ways calderas are formed

Violent eruption which cause the top to blow off or Viscous lava eruption cause it to cool and solidly close to base which makes the base unable to support its weight