I. What is a Volcano?

A volcano is any opening in the

Earth’s crust where magma, ash and

gas are able to reach the surface

Volcanoes may have more than one

opening which are called vents

The main vent is known as the crater

I. What is a Volcano?

Far below the crater is the magma

chamber

Magma rises from the magma

chamber, through a conduit, into the

throat of the volcano, until it reaches

the crater

1. Large Magma Chamber

2. Bedrock

3. Conduit (pipe)

4. Base

5. Sill

6. Dike

7. Layers of Ash Emitted by the Volcano

8. Flank

9. Layers of lava emitted by the Volcano

10. Throat

11. Parasitic Cone

12. Lava Flow

13. Vent

14. Crater

15. Ash Cloud

II. What Causes Volcanoes?

Volcanoes are caused by one of three things:

1. Convergent tectonic plates, usually at a

continental-oceanic plate subduction zone

2. Divergent tectonic plates, usually at a mid-

oceanic ridge

3. Mantle plumes a.k.a. “hot spots”

III. Three Major Types of Volcanoes

1. Shield Volcano

• Broad with gentle slope similar to a

shield

• Produced by low-viscosity lava flows

• Mild eruptions

• More common in oceanic than

continental settings

Mauna Kea in Hawaii

III. Three Major Types of Volcanoes

2. CompositeVolcano (Stratovolcano)

• Tall with steeper slopes similar to a

cone

• Produced by high-viscosity lava flows

• Explosive eruptions of alternating

layers of ash, cinders and lava

• More common in subduction zones

Mount Fuji in Japan

Mount Mayon in Phillipines

III. Three Major Types of Volcanoes

3. Cinder Cone

• Small with steepest slopes

• Produced by explosive lava flows

• Violent eruptions

• Commonly found around shield or

composite volcanoes

Sunset Crater in Arizona

Capulin Volcano in New Mexico