volcanoes Flashcards
(13 cards)
what is the difference between magma and lava
magma is molten rock beneath the Earth’s surface, while lava is that same molten rock that has erupted onto the surface.
what plate margins are volcanoes found
destructive and constructive
at the destructive plate boundary, why does the oceanic plate go under the continental plate
because its more dense
how do volcanos form at destructive plate boundaries
- oceanic plate moves into the mantle, where its melted & destroyed
- pool of magma forms and rises through cracks in the crust (vents)
3.magma erupts onto surface forming a volcano
how do volcanos form at constructive plate boundaries
- magma rises up into the gap, created by the movement of plates, forming a volcano
how does a volcano form pyroclastic flows ( super-heated currents of gas, ash, rocks)
volcanos emit lots of ash which cover land and block out sun
where are hotspots found
in oceanic or continental crust
how does a hotspot occur
a plume of hot magma from the mantle moves towards the surface, causing an unusually large flow of heat to the crust forming a volcano
how is a chain of volcanic islands created and give an example
hotspots remain stationary over time, but crust moves above them
example- Hawaii, in the middle of the pacific plate
where does a composite volcano occur
at a destructive plate boundary
what is a composite volcano
-subducted oceanic crust containing lots of water which causes crust to erupt
-the eruptions start with ashy explosions that deposit a layer of ash, then erupt a layer of thick lava
forms a steep-sided cone
where does a shield volcano occur
at hotspots or constructive plate boundaries
what is a shield volcano
made up of only runny lava, so flows quickly and spreads over a wide area
forms a low-gently sided volcano
