Earth ScienceCoach Williams

Room 310B

Volcanoes

Chapter 18

Objectives:1. Describe the major parts of a volcano.2. Compare/contrast shield, cinder-cone, and

composite volcanoes.3. Contrast the volcanism that occurs at plate

boundaries.4. Explain the relationship between volcanism and

hot spots.

Section 18.3: Volcanoes

Volcano: mountain of cooled lava Vent: opening in crust Crater: bowl shaped depression Calderas: larger depressions

Anatomy of a Volcano

Shield: broad, gentle slope. Circular base Cinder-Cone: steep sides. Smaller Composite: fragments layered with lava.

◦ Larger

Types of Volcanoes

Types of Volcanoes

Tephra: rock fragments thrown in air◦ Dust: <2mm◦ Ash: >2mm◦ Lapilli “little stones”: rock size◦ Volcanic blocks: large, angular◦ Volcanic bombs: large rounded

Pyroclastic flows: deadly flow of volcanic material (gas, ash, tephra)

Volcanic Materials

Most at plate boundaries 80%: convergent boundaries 15%: divergent boundaries Hot spots: hot regions of Earth’s mantle

◦ Volcanoes far from plate boundaries

Where Volcanoes Occur

Where Volcanoes Occur

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