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VOLCANOES AND PLATE TECTONICS Ch. 3.1, 3.3, 3.4. A. Volcanoes. A weak spot in the crust 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- - PowerPoint PPT Presentation
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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