Types of Lava and Volcanoes

Shield Volcanoes

• Shield volcanoes are one of the more common types of volcanoes. They are usually very wide and broad with relatively low profiles, giving them a resemblance to a shield. They are formed by fluid lava seeping from their openings instead of exploding out, which hardens and creates broad plains of sediment around them.

Cinder Cones

• Cinder cones can either be considered a type of volcano or a feature of a larger volcano, but regardless of classification they result in a tall, narrow, cone-like mountain. Cinder cones are created by lava being shot up through a single vent in the Earth that forms around the cone as it falls back down and hardens. Accumulation over time leads to the rising of the cone.

Stratovolcanoes

• Stratovolcanoes, which are sometimes referred to as composite volcanoes, are large, conical mountains known for their explosive tendencies. They can be as large as shield volcanoes, but have a steep profile that is caused by cinder cone-like explosions of lava that build up over time. The explosive nature of these volcanoes is due to a gradual buildup of pressure caused by rising magma (lava before it has been expelled) that eventually pops. Mt. St. Helens is a famous stratovolcano located in Washington state.

Types of Lava

• There are numerous types of lava that are associated with different volcanoes. Rough lava (known technically as 'A'a, a Hawaiian word) flows very slowly, with a rough, sludgy texture that glows bright orange as it moves. Pahoehoe lava runs much more smoothly and more fluidly than 'A'a, with a silky, wrinkled texture developing on the surface as it cools. It does not typically glow like 'A'a, making it difficult to see on radar. Pillow lava is associated with underwater volcanoes. When lava is expelled underwater, it immediately cools and hardens, forming round blobs.