Volcanoes form at boundaries where tectonic plates meet, especially along the Ring of Fire surrounding the Pacific Ocean. All volcanoes have vents and may also have craters, magma chambers, and different types of underground rock formations such as dikes, sills, laccoliths, and batholiths. There are three main types of volcanoes: shield volcanoes which erupt fluid lava to build broad bases; cinder cone volcanoes which erupt thick chunks of lava to form steep cones; and composite volcanoes made of layers of ash/lava. Volcanoes erupt when pressure builds from subducting plates pushing rock down and melting it in magma chambers until it escapes upward.

1. Volcanoes 5th grade, A Closer Look MacMillian/McGraw-Hill

2. Where are Volcanoes found? volcano- opening in Earth's crust most are located at plate boundaries Ring of Fire surrounds Pacific Ocean

3. Parts of Volcano All volcanoes have at least one vent (opening). Crater- cup-shaped depression may form around a vent Magma chamber- where magma collects Lava- when magma reaches Earth’s surface

4. Caldera- a hole forms beneath the magma chamber, the magma leaks out and the chamber collapses inside itself. Dike- Some magma hardens in vertical cracks Sill- forms when magma hardens between horizontal layers of rock Laccolith- when sills don’t spread horizontally, instead they push upward and form a dome shape Batholith- largest/deepest underground magma formations. They are huge, irregularly shaped, reaches deep into crust.

6. Thrown high in the air, falls as chunks

7. form cone shape with narrow base and steep slopesComposite Volcanoes Built by layers of ash and cinders, sandwiched between layers of hardened lava

8. Eruption- outpouring of lava, ash, gases, or combination of these

9. Volcanoes erupt when one plate is pushed under another plate. Rocks push down, heat and melt. Magma forms and pools in the magma chamber under the crust. Cracks form above the chamber or pressure grows too great and magma rushes upward toward the Earth’s surface.

10. Active, Dormant, Extinct Active volcanoes- currently erupting or have recently erupted Dormant volcanoes- doesn’t erupt for a long time Extinct volcanoes- dead/stopped erupting long ago