Global Volcanoes Scripps Classroom Connection

Where do volcanoes occur? Volcanoes occur at: 1. Hotspots 2. Plate Boundaries -Convergent (subduction zones) -Divergent Scripps Classroom Connection

What are hotspots? Hotspots  Spot on Earth with volcanism  Can occur in the middle of tectonic plates  Hotspots don’t move  Tectonic plates move over hotspots  Makes a chain of volcanoes, like Hawaii Scripps Classroom Connection Hawaii

Hotspot volcanoes Ocean Hotspots  Shield volcanoes, Hawaiiian Islands  Fast moving, basaltic lava  Effusive  Stratovolcanoes, Canary Islands  Alternating lava and ash  Explosive Continental hotspots  Explosive  Yellowstone Caldera, Wyoming Scripps Classroom Connection

Subduction Zones Subduction Zone Volcanoes  Most major volcanoes found near subduction zones  Stratovolcanoes  Most dangerous Two different types: 1. Ocean-Ocean 2. Ocean-Continent Scripps Classroom Connection

Ocean-Ocean Subduction Volcanoes Ocean-Ocean  Island Volcanic Arcs  Japan  Aleutian Islands, Alaska Scripps Classroom Connection

Ocean-Continent Subduction Volcanoes Ocean-Continent  Continental Volcanic Arcs  Andes Mountains, South America  Cascades, N.W. United States Scripps Classroom Connection

Spreading Centers Tectonic Spreading Centers ● Under the ocean  Mid-ocean ridges ● On Land  Continental rifts ● Almost continuous volcanism ● Create new oceanic crust Scripps Classroom Connection

Mid-Ocean Ridge Volcanoes  Volcanoes form on fissures parallel to the ridge axis  Hundreds of volcanoes along each ridge, near- continuous volcanism  Erupt basalt  Create new oceanic crust Scripps Classroom Connection

● Most volcanoes occur at plate boundaries: 1. Subduction zones 2. Mid-ocean ridges ● Some volcanoes occur at hotspots: 1. Ocean floor 2. Continental Scripps Classroom Connection Global Volcano Conclusions