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- Lava- 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 Fire Volcano 101 Major volcanic belt Formed by many volcanoes around the rim of the Pacific Ocean Forms along plate boundaries Volcano 101

C. Volcanoes occur at…. Divergent Boundary - mid-ocean ridge

2. Subduction Zone -edges of oceans

-Hawaii was formed this way 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 gases bombs -mass of thick magma 3. the longer the eruption, the higher the cone

Composite volcanoes 1. 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. Rainier How Volcanoes Form