A volcano is a mountain that opens downward to a reservoir of molten rock below the surface of the Earth. When pressure builds up, eruptions occur. Gases and rock shoot up through the opening and spill over or fill the air with lava fragments. Eruptions can cause lateral blasts, lava flows, hot ash flows, mudslides, avalanches, falling ash, and floods.
Types of Volcanoes
Shield Volcanoes: These are large, broad volcanoes with shallow-sloping sides. They are formed by the flow of low-viscosity basaltic lava.
Stratovolcanoes: Also known as composite volcanoes, they are tall, steep-sided volcanoes built by both lava flows and explosive eruptions.
Cinder Cone Volcanoes: These are the smallest type of volcano, and they often form on the sides of larger volcanoes. They are made up of ash, cinders, and volcanic rocks.
Volcanic eruptions can be explosive or effusive. Explosive eruptions involve the release of gas, ash, and magma in a violent manner, while effusive eruptions involve the relatively gentle outpouring of lava onto the surface.
Study Guide
What is a volcano?
Describe the different types of volcanoes.
Explain the difference between explosive and effusive volcanic eruptions.
Discuss the role of volcanoes in shaping the Earth's surface.
Understanding the different types of volcanoes, their eruptions, and associated hazards is essential for comprehending the geological processes that shape our planet.
Develop and use models of Earth’s interior composition to illustrate the resulting magnetic field (e.g., magnetic poles) and to explain its measureable effects (e.g., protection from cosmic radiation).