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