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Where are Volcanoes Found? 3b - Students know the principal structures that form at the three different kinds of plate boundaries. 3c - Students know the explanation for the location and properties of volcanoes that are due to hot spots and the explanation for those that are due to subduction. 1. Divergent Plate Boundaries (15%) 2. Convergent Plate Boundaries (80%) 3. Hot Spots (5%) 1. Divergent Boundaries • • • • Rift volcanism (ocean ridges) Mostly under the oceans Basaltic magma – Shield Volcanoes On land – Africa & Iceland • Subduction Zones (convergence of oceanic plates) • Andesitic magma or Rhyolitic magma – Composite Volcanoes a. Circum-Pacific Belt -Pacific Ring of Fire b. Mediterranean Belt Mediterranean Belt Ring of Fire • Unusually hot areas of Earth’s mantle • Hot plumes rise toward the crust…forming magma and volcanoes • As the lithosphere moves over a hot spot….a trail of progressively older volcanoes forms • Hawaii & Yellowstone • If hot spot is under the ocean = non-explosive basaltic magma • If hot spot is under the continents = explosive rhyolitic magma