Volcanoes Flashcards
(47 cards)
What is a volcano?
Mountains formed in Earth’s lithosphere from magma rising to the surface.
What is the difference between magma and lava?
Lava is above the surface and magma is below the surface.
Where do most volcanoes occur?
Along plate boundaries.
Describe a convergent boundary.
When a subducting plate melts as it sinks into the mantle.
Describe a divergent boundary.
When the lithosphere thins and weakens as it pulls apart.
How do volcanoes form at a divergent boundary?
When two plates move away, causing it to thin and crack so magma can seep through.
What type of eruption commonly occurs at divergent boundaries?
Quiet eruptions.
How do volcanoes form at convergent boundaries?
When two plates collide, the denser plate subducts beneath the other.
What is subduction?
The process of one plate sinking beneath the other. When it subducts, it makes magma.
What happens when the oceanic crust subducts beneath the continental crust?
They form coastline volcanoes.
What happens when oceanic crust subducts beneath oceanic crust?
It forms volcanic islands along the subduction zone.
What is a hot spot?
Locations where deep mantle material rises through the crust and melts. Hot spots do not move over time.
Do hot spots move?
No.
What are some examples of hot spot volcanoes?
Yellowstone, Hawaii, and Iceland.
Why can’t bubbles form beneath the ground?
Magma contains dissolved gases but due to the pressure, the gases are unable to form bubbles.
What happens when magma rises toward the surface?
The pressure drops and allows the gases to form bubbles.
What force causes magma to push through the surface and erupt?
Bubbles.
What are the characteristics of quiet eruptions?
Oozes out of cracks in the ground and flows across the ground.
Forms shield volcanoes, which are large, wide volcanoes that have a gentle slope.
What are the characteristics of explosive eruptions?
Lower temperature, high silica magma which contains lots of dissolved gases.
Forms cinder cone and composite volcanoes.
What is an active volcano?
A volcano that shows signs of erupting or will erupt soon.
What is a dormant volcano?
A volcano with an active magma chamber but no signs of erupting in the near future.
What are extinct volcanoes?
A volcano with an empty or cooled magma chamber that will never erupt again.
What layer of earth does magma form in?
Upper mantle.
What happens when magma reaches the surface?
It will erupt as lava and build up to form a volcano.
