VOLCANOES Earth’s Fiery Release B56a

VOLCANO mountain produced by repeated eruptions –magma rises to the surface because it is less dense than the surrounding material

WHERE VOLCANOES FORM Divergent Plate Boundaries Convergent Plate Boundaries –continental-oceanic –oceanic-oceanic Hot Spots

HOT SPOT area of asthenosphere that is hotter and less dense than the surrounding material magma rises located within a plate (not at the edges where two plates come together) (B9, Fig. 28)

HOT SPOTS CREATE ISLAND ARCS Hot spot is fixed as plate moves over a hot spot, a chain of islands forms Hawaiian Islands (B9, Fig. 29)

PARTS OF A VOLCANO CRATER - hole at top of volcano VENT - hole where magma leaves the crust MAGMA CHAMBER - area of hot magma in the mantle (B9, Fig. 30)

EFFECTS OF EROSION volcanic neck - sides of a volcano erode faster than the core –leaves the core sticking up out of the ground

EFFECTS OF A HUGE ERUPTION caldera - large depression at the top of a volcano –large eruption collapses the top of the volcano –often fill with water –Crater Lake (misnomer)

THREE TYPES OF VOLCANOES SHIELD VOLCANO COMPOSITE VOLCANO CINDER CONE dependant on magma type –basaltic or granitic

1 - SHIELD VOLCANO basaltic magma –oceanic plates thin, dense gas & water allowed to escape quiet eruptions lava flows flat, broad shape

2 - CINDER CONE granitic magma –continental crust thick, not very dense gas and H 2 O trapped explosive/violent eruptions tephra and ash produced steep sided, tall

3 - COMPOSITE VOLCANO basaltic and granitic magma (continental and oceanic crust) gas and H 2 O sometimes trapped quiet and violent eruptions lava flows and tephra moderately sloped

ASSIGNMENT Make a table comparing the three types of volcanoes. INCLUDE: name, magma type, amount of trapped gases, eruption type, eruption material and shape.