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what happens during an explosive volcanic eruption
clouds of hot debris, ash and gas rapidly shoot from a volcano - cause molten rock to be blown into tiny particles that harden in the air - can blast millions of tons of lava and rock - can demolish a mountainside in a matter of seconds
what happends during a non-explosive volcanic eruption
produce relatively calm flows of lava - can release hugh amounts lava
how can you predict the silica content based on viscosity
based on its flow - if it flows slower, it has a high silica content
describe four types of pyroclastic flow
volcanic bombs - large blobs of magma that harnden in the air, lapilli - means little stones in Italian, pebble-like bits of magma, volcanic ash - form when gases in still magma expand rapidly, volcanic blocks - the largest pieces
produced when enormous amounts of hot ash, dust and gases are ejected from a volcano
are built of layers of lava released from repeated nonexplosuve eruptions - lava is runny and spreads out over a wide area - Mauna Kea in Hawaii
cinder cone volcanoes
are built from pyroclastic material during modeately explosive eruptions - has steep slopes - Paricutin in Mexico
are built from explosive eruptions follwed by quieter flows of lava - most common type of volcano - also called stratovolcanoes - Mount Fuji in Japan & Mount Hood in the US
volcanic eruption affects climate change how
volcanic ash and gas spread throughtout the atmosphere and can block out sunlight and cause global temperatures to drop - Mount Pinatubo in the Philippines
describe the eruption of a composite volcano
combination of both types of eruptions form alternating layers of pyroclastic material and lava - have broad bases and sides that get steeper toward the top
a large semi-circle depression that forms when the magma chamber below a volcano partially empties and causes the ground above to sink
a wide flat landform that resutls from repeated non explosive eruptions of lavathat spead over a large area
size of a caldera to a crater
caldera is usually bigger than a crater because everytime there is an eruption the caldera gets bigger
why doesnt rock of the mantel melt at Earth's surface
beceause it is not hot enough and there is not enough pressure
are surrounding the Pacific Ocean known as the Ring of Fire
because it has so many colcanoes - area of tectonic plate boundaries
an area of deep cracks that forms between two tectonic plates that are pulling away from each other
an underwater moutain chain where new ocean floor is formed - by lava that flows underwater
how does magma from at a convergent boundary
subduction - the movement of one tectonic plate underneath another
how does subduction produce magma
causes increased and pressure near the oceanic crust to be released - water mixes with mantel rock, lowering the rocks melting point
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