VOLCANOES AND PLATE TECTONICS Ch. 3.1, 3.3, 3.4

VOLCANOES AND PLATE TECTONICS

Ch. 3.1, 3.3, 3.4

A. Volcanoes

1. A weak spot in the crust

2. Magma-molten material from mantle comes to the surface

Vocabulary to know….. Magma-

molten material made of – gases – rock-forming

substances– water – silica is the force for

magma to erupt

Lava- – Is magma that reaches

the surface

B. Ring of Fire1. Major volcanic belt 2. Formed by many volcanoes around the rim of

the Pacific Ocean3. Forms along plate boundaries

Volcano 101

C. Volcanoes occur at….

1. Divergent Boundaries-mid-ocean ridge

2. Subduction Zone-edges of oceans

3. Hot Spots-magma from deep

within mantle melts through the crust like a blow torch

-Hawaii was formed this way

A Pacific Plate drifts over a hot spot to form Hawaii

Label your worksheet.

What is viscosity? A physical property of a liquid

The resistance of a liquid to flow

The greater the viscosity, the slower the flow

Lava viscosity depends on the silica content and temperature

Pahoehoe: fast moving lava, low viscosity Aa: slow moving lava, high viscosity

Other vocabulary you should know….

Active volcano -is erupting or will erupt

Dormant volcano-sleeping-will awaken in the future, become active

Extinct volcano-dead-will not erupt again

Volcanic 4 Landforms Shield volcanoes

1.Many layers of lava

2. Quiet eruptions

3. Gently sloping mountain formed by repeated lava flows

4. 90% is lava flow

5. Lava flows far from the vent

6. Ex. Hawaiian Islands

Cinder Cone Volcanoes

1. piles of cinders form a cone-shaped hill

2. a pyroclastic flow, explosive eruptions, producing ash

cinders gasesbombs -mass of thick magma

3. the longer the eruption, the higher the cone

Composite volcanoes1. known as stratovolcanoes

2. tall mountain volcano

3. explosive eruptions

4. alternating layers of ash, cinders, bombs

5. multiple eruptions over hundreds of years

6. occur in chains, mostly in the Ring of Fire

7. Ex. Mount St. Helen’s Mt. RainierHow Volcanoes Form