Volcanoes
Composite and shield volcanoes are found along plate margins. They have distinctive characteristics and can have both positive and negative effects on people and the landscape.
Types of volcano - composite and shield
There are two main types of volcano - composite and shield. The two types of volcano form in different places and have very different characteristics.
Composite volcanoes
Composite volcanoes are found on destructive plate margins, where the oceanic crust sinks beneath the continental crust. Composite volcanoes have the following characteristics:
- Acidic lava, which is very viscous (sticky).
- Steep sides as the lava doesn't flow very far before it solidifies.
- Alternate layers of ash and lava. For this reason, they're also known as stratovolcanoes. Strato means layers.
- Violent eruptions.
- Longer periods between eruptions.
An example of a composite volcano is Mount Pinatubo in the Philippines.
Shield volcanoes
Shield volcanoes are found on constructive plate margins, where two plates move away from one another. Shield volcanoes have the following characteristics:
- basic lava, which is non-acidic and very runny
- gentle sides as the lava flows for long distances before it solidifies
- no layers, as the volcano just consists of lava
- less violent eruptions
- shorter periods between eruptions
Mauna Loa is a shield volcano, but was formed over a hot spot, rather than at a constructive plate margin, like other volcanoes.
Mauna Loa is a shield volcano