Types of Volcanoes Review Where do volcanoes occur

Types of Volcanoes

Review Where do volcanoes occur? 1. Hot Spots 2. Convergent Plate Boundaries 3. Oceanic-Oceanic-Continental Divergent Plate Boundaries

Types of Volcanoes 3 Major Types: 1. Shield 2. Composite 3. Cinder Cone

Magma Composition Magma is composed of many elements and compounds One compound is silica (Si. O 2) The more silica in magma, the more viscous or thick

Shield Volcanoes The magma inside a shield volcano is very fluid because it is low in silica. Since the magma is very fluid, the lava coming out of the volcano tends to flow great distances. When shield volcanoes erupt, the flowing lava gives the volcano the shape of a gently sloping mountain. Flowing lava = Low-explosivity

Composite Volcanoes The magma inside a composite volcano is rich in silica and much thicker than magma from a shield volcano. Gases get trapped inside this thicker magma. Eruptions from composite volcanoes can be flowing lava or explosions. The explosive eruptions come from the trapped gases and produce cinders and ash.

Composite Volcanoes Alternating layers of lava and cinders. Composite volcanoes have much steeper slopes than shield volcanoes. Mount Fuji in Japan and Mount St. Helens in the USA are examples of composite volcanoes.

Cinder Cone Volcanoes The magma inside a cinder cone is low in silica but has large amounts of gas trapped in it. Eruptions from cinder cone volcanoes are violent and explosive because of all the gas trapped in the magma. Think of shaking a can of pop. The large amounts of hot ash and lava thrown out of the vent fall to the ground forming the cone shape that these volcanoes have.

Cinder Cone Volcanoes Cinder cone volcanoes are usually only active for a short time and then become dormant (inactive). Paricutin volcano. in Mexico is an example of a cinder cone