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29 terms

Chapter 9 - Volcanoes

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Volcano
a vent or fissure in the Earth's surface where magma and gases are expelled.
mostly found on plate boundaries
active volcanoes form where tectonic plates collide
cinder cone volcano
a small, steeply sloped volcano that with explosive eruptions of pyroclastic material
composite volcano
Volcano built by alternating explosive and non-explosive eruptions
shield volcano
A wide, gently sloping mountain made of layers of lava and formed by non-explosive eruptions.
Non-explosive eruption
huge lava flows. If lava is thin and runny, it has a low silica content
explosive eruption
would have clouds of hot debris, ash & gas (pyroclastic material)
happens when the water content in the magma is high
tiltmeter
measure changes in a volcanoes slope
Viscosity
how the lava flows-either slowly or quickly
milky consistency = low viscosity
milkshake consistency = high viscosity
magma
when underground, gathers in the magma chamber
lava
melted rock after it reaches the earth's surface
rock melts when TEMPERATURE INCREASES & PRESSURE DECREASES
AA lava
forms into a brittle crust that has sharp jagged pieces
Pahoehoe lava
has a glassy surface and flows like dripping wax
blocky lava
cool, stiff lava that makes heaps of sharp chunks
pillow lava
lava that forms from an underwater eruption and is characterized by a pillow shape
pyroclastic material
forms when magma explodes and hardens in the air into ash, dust and gases
lapilli
pyroclastic material that means "little stones"
volcanic ash
can reach the upper atmosphere and circle the Earth for years
volcanic bombs
large blobs of magma that harden in the air
volcanic blocks
largest pieces of pyroclastic material
they are pieces of rock
crater
a funnel shaped pit at the top of the volcano
caldera
a depression that happens when the magma chamber collapses and empties
rift zone
deep cracks between two tectonic plates that pull away from each other
hot spots
located above mantle plumes
ex. volcanoes of Hawaii and other volcanoes far away from tectonic plates
active volcano
can erupt in the near future
dormant volcano
has not erupted in many years, but still could
extinct volcano
will never erupt again
lava plateau
large, flat area covered by lava
climate change effect
when volcanic ash reaches the upper atmosphere, it can block sunlight and make global temperature go down
good effect of volcanoes
make very fertile soil that is good for farming