volcanoes

volcanic activity is frequent in

subduction boundaries, mid-ocean spreading center, continental rifts

hot spot

mantle plume: a zone of local weakness in the mantle

examples of hot spots

Iceland, Hawaiian Seamount chain, Yellowstone

Mafic Magma

little silica, hot, flowing lava, basalts, less viscous, originates from magma derived in deep mantle

Felsic Magma 

silica-rich, cooler, more viscous, explosive eruptions, rhyolites, originates from melting crust 

stratovolcanoes (composite)

tall, steep cones built of layers of felsic lava and volcanic ash (intermediate silica content: can be explosive, but lava flowing down sides) examples: mt fuji or mt st helens

calderas

remnants of very large explosions of stratovolcanoes

shield volcanoes

mafic lava (basalts), not viscous, holds little gas, broadly rounded with gentle slopes, eruptions: quiet and travel long distances to spread out in thin layers

hot springs

hot rock material is near the earth’s surface, heats ground water to high temps 

geyser

jet-like emissions of steam and hot water occur at intervals from small vents

what kind of volcano is Eviafjallajökull Iceland, April, 2010

shield volcano

You see a tall, isolated mountain above from a distance. Most likely it is a

a stratovolcano (composite) made mostly of rhyolite

low viscosity lava flows are

low silica basalts

which of the following is not matched correctly 

a. mantle plume → hotspot

b. shield volcano→ low viscosity basalt flows

c. rhyolite → explsive eruptions

d. calderas→ meteor crater 

d