Volcanoes

What is a volcano?  A volcano is basically anywhere on the crust where magma comes to the surface

Where are volcanoes found?  Volcanoes are found in two typical locations: ◦ Near plate boundaries ◦ At hot spots – an area where magma from the mantle melts through the crust above it. (Hawaiian Islands)  Ring of Fire – volcanoes around the Pacific Ocean

Earth’s Active Volcanoes

How does a volcano erupt? PRESSURE!!!  Magma rises to the surface  Gases dissolved in the magma rush out, carrying the magma with them (like a shaken bottle of soda)

How are volcanoes classified? There are 3 different types of volcanoes, each one is based on how they were formed: ◦ Shield volcanoes ◦ Cinder cone volcanoes ◦ Composite volcanoes or Stratovolcanoes

Different types of eruptions Quiet – mostly lava Pyroclastic (explosive) –mostly ash, cinders, bombs, and gases

What makes an eruption quiet or explosive? Magma is mostly made of silica (silicon + oxygen = silica)  The more silica in the magma/lava, the thicker it is.  The thicker it is, the more explosive the eruption.

Different types of lava flow There are two types of lava flow: ◦ AA – a thick, slow moving lava flow (like mashed potatoes) ◦ Pahoehoe – a thin, fast-moving lava flow (like gravy)