Section 1: Volcanoes and Plate Tectonics

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6 th Grade Ch. 3, Sec. 1 Notes

Volcanoes and Plate Tectonics

*A volcano is a weak spot in the crust where molten material comes to the surface

-Magma: molten mixture of rock-forming substances, gases, and water

*magma is underneath the surface

-Lava: magma that reaches the surface

*when lava is cooled, solid rock is formed

Volcanoes and Plate Boundaries

1. Volcanoes tend to occur in belts that extend over oceans and continents

-major belt is the Ring of Fire located in the Pacific Ocean

2. Volcano belts form along the boundaries of Earth's plates

-divergent boundaries: form along mid-ocean ridges and rift valleys

-convergent boundaries: form where subduction is taking place

*Volcanoes created along convergent boundaries form island arcs

-a string of islands where the curve follows the curve of a deep-ocean trench

Examples: Japan, the Phillipines, and the Caribbean

Hot Spot Volcanoes

*Hot spot volcanoes can occur anywhere on the plate, not just the boundary:

-a hot spot is an area where material from deep within the mantle rises and melts, forming magma

-magma erupts through the crust, reaches the surface and creates a volcano

-hot spots occur in the ocean and under continental plates

Examples: Hawaii, Yellowstone National Park

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