Plate Tectonics and Igneous Activity Pgs. 293 - 295 Chapter 10.3 Plate Tectonics and Igneous Activity Pgs. 293 - 295

There have been 800 active volcanoes identified mostly in the Ring of Fire. A second group has been found on the ocean floor. A third group is found unevenly distributed on continents. Plate tectonics have helped to determine why volcanoes are distributed the way that they are.

Convergent Plate Boundaries Remember that there is not a lot of places where magma can be created. Plate boundaries are a great place where magma can be made. Convergent plate boundaries are where oceanic crust is pushed down into the mantle. This creates a lot of magma and that magma will form volcanoes, like Mount St. Helens.

Ocean-Ocean Where 2 oceanic plates meet one plate will move under the other creating a chain of volcanoes on the ocean floor. These are the types of volcanoes that will form islands. The Aleutian Islands were formed this way.

Ocean-Continent This is where an oceanic plate move under a continental plate and it results in a continental volcanic arc. An example is the Andes Mountain in South America.

Divergent Plate Boundaries Most magma is made during seafloor spreading.

Intraplate Igneous Activity Intraplate volcanism is when volcanic activity occurs in the middle of a plate, not at a boundary. An example would be in Hawaii or at Yellowstone National Park. This will happen where a mass of hotter than normal mantle material, called a mantle plume, rises toward the surface. This is how a hot spot is formed. There are more than 40 hot spots.