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36 terms

Volcanos

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Viscosity
The Resistance of a liquid to flow
low viscosity- like a glass of milk, flows quickly
high viscosity- like a milkshake, very stiff and flows slowly
Pyroclastic Flow
A flow of hot gases, ash, cinders and bombs put off by an explosive eruption
Volcano
A weakspot in the crust where magma has come to the surface
Hot Spot Volcano
Material from the mantle rises close to the surface, melting through the crust. Can form a string of islands, for example Hawaii.
Lava
Magma that reaches the surface
Shield Volcanoes
A wide gently sloping mountain formed by layers of Low-Silica, fast and runny lava from quiet eruptions (Low Viscosity)
Where do volcanoes occur?
Diverging plate boundaries, Converging plate boundaries, and Hot Spots
Examples of diverging plate volcanoes
Mid Ocean Ridges and Rift Valleys
Converging plate volcanoes
Occur at subducting boundaries, and may form island arcs. Example: Japan and Caribbean
Composite Volcano
Tall cone-shaped mountain in which layers of lava alternate with layers of ash.
Parts of a volcano from bottom to top
Magma Chamber, Pipe, Vents (Top and /or sides), Crater
Pahoehoe
Fast moving hot lava with low viscosity
A'a'
Lava that is cooler, slower moving, with higher viscosity
Lahar
Pyroclastic Flow with more water than usual
Volcanic Neck
Forms when magma cools in a volcano's pipe
magma chamber
the pocket beneath a volcano where magma collects
Vocanic bombs
are large blobs of magma that harden in the air
Lapilli
mean s "little stones" in Italian are pebblelike bits of magma that harden before they hit the ground
volcanic ash
forms when the gases of stiff magma expand rapidly and the walls of the gas bubbles explode into tiny glasslike slivers
Caldera
The large hole at the top of a volcano formed when the roof of a volcano's magma chamber collapses.
crater
funnel-shaped pit or depression at the top of a volcanic cone
lava plateau
a wide, flat landform that results from repeated nonexplosive eruptions of lava that spread over a large area
rift zone
an area of deep cracks that forms between two tectonic plates that are pulling away from each other
hot spot
an area where magma from deep within the mantle melts through the crust above it
dormant volcano
A volcano that has not erupted for a long time, but may erupt again one day.
active volcano
One that is erupting or shows signs that it may erupt in the near future.
extinct volcano
A volcano that has not erupted for thousands of years and probably will not erupt again.
tiltmeter
Measures changes in a volcano's slope
cindercone volcano
a type of volcano made mostly of cinders and other rock particles that have been blown into the air
compostite volcano
form alternating layers of pyroclastic materials (fire broken) such as ash and lava flows; symmetrical cones that are steeper than shield volcanoes
Ring of Fire
A major belt of volcanoes that rims the Pacific Ocean
Pillow lava
Lava that cools underwater, taking on a distinctive pillow-like shape as it hardens
blocky lava
cool, stiff lava that does not travel far from the erupting vent. Usually oozes from a volcano and forms jumbled heaps of sharp-edged chunks.
magma
Molten rock beneath the earth's surface
silica rich magma
magma with a stiff consistency, flows slowly and tends to harden in a volcano's vent- tends to cause explosions
low silica magma
more fluid, runnier consistency. gases can escape and are less likely to be explosive