Three Types of Volcanoes

VOLCANOES EQ: What are the types of volcanoes and how are they volcanoes and how are they formed? formed?

A volcano is a weak spot in the crust where molten material, or magma, comes to the surface. So, What Is a Volcano?

The Ring of Fire Subduction zones The Ring of Fire is a volcano belt formed by many volcanoes that border the Pacific Ocean.

How are volcanoes formed?

Deep in the earth it is very hot and rocks melt. The melted rock is called magma and is lighter than the rocks around it so it rises. Sometimes it finds a crack or hole in the earth’s crust and bursts through it (vent). This is how a volcano begins.

Why do volcanoes erupt?

Pressure builds deep in the earth where the magma is. Suddenly the gases escape and violently explode. Pressure builds deep in the earth where the magma is. Suddenly the gases escape and violently explode.

What are the different kinds of volcanoes?

Classifying Volcanoes Composite or Strato Composite or Strato Cinder Cone Shield ActiveIntermittentDormantExtinct

VOLCANIC ACTIVITY ACTIVE - A volcano that has erupted in the recent past and is expected to erupt again. INTERMITTENT – A volcano that erupts in fairly regular time periods. DORMANT - A “sleeping” volcano. A volcano that has not erupted in the recent past, but could erupt again. EXTINCT - A volcano that is not expected to erupt again.

Shield Volcanoes A shield volcano is a large, gently sloped volcano made up from many slow, steady flows of hot lava. Low and broad – like a warrior’s shield. A shield volcano is a large, gently sloped volcano made up from many slow, steady flows of hot lava. Low and broad – like a warrior’s shield. Materials Erupted : mainly liquid lava, so the volcano is made of layers of hardened lava. Materials Erupted : mainly liquid lava, so the volcano is made of layers of hardened lava. –Non-explosive eruptions Example: the volcanoes of Hawaii Example: the volcanoes of Hawaii **Click picture for video.

Shield Volcanoes Low silica level Low silica level Low viscosity Lava Low viscosity Lava High or low levels of gas High or low levels of gas Low to medium explosivity Low to medium explosivity Flattened mound Flattened mound Resembles a warrior’s shield Resembles a warrior’s shield

Mauna Loa, Hawaii

Piton de la Fournaise

Surtsey, Finland

Composite Volcanoes

A composite volcano is a huge mountain-like volcano. Layers build up like frosting on a cake forming a cone with steep sides. A composite volcano is a huge mountain-like volcano. Layers build up like frosting on a cake forming a cone with steep sides. Materials Erupted: sometimes lava, sometimes rock fragments. Materials Erupted: sometimes lava, sometimes rock fragments. – May have very explosive eruptions Example: Mount St. Helens Example: Mount St. Helens **Click picture for video.

Composite Volcanoes High in silica High in silica High viscosity magma High viscosity magma High levels of gas High levels of gas Highly explosive Highly explosive Cone shaped Cone shaped Formed by layers of lava and ash Formed by layers of lava and ash

Mt. Rainier, Washington

Mt. Fuji, Japan

Mt. St. Helens, Washington

Cinder Cone Volcanoes

Cinder cone volcanoes form when solid rock and ash shoot up into the air and fall back around the volcano opening. The cinder cone volcano has steeply sloped sides.

Cindercones Low silica lava Low silica lava High levels of gas High levels of gas “Fire-fountain” eruptions “Fire-fountain” eruptions Commonly found on the flanks of shield volcanoes Commonly found on the flanks of shield volcanoes Made from a pile of rock pieces Made from a pile of rock pieces Structurally weak Structurally weak

Cinder Cone Volcanoes A cinder cone volcano is a relatively small, volcano with steep sides. It is where rock and ash shoot up into the air and fall back around the opening. A cinder cone volcano is a relatively small, volcano with steep sides. It is where rock and ash shoot up into the air and fall back around the opening. Materials Erupted: small pieces of hardened lava (rock fragments) - called cinders Materials Erupted: small pieces of hardened lava (rock fragments) - called cinders –Moderately explosive Example: Paricutin (Mexico) Example: Paricutin (Mexico) **Click picture for video.

Pu'u ka Pele, Hawaii (on the flanks of Mauna Loa)

Floreana Island, Galapagos Floreana Island, Galapagos

Puu OO, Hawaii