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Volcanoes and Plate Tectonics
Volcanic Eruptions
Volcanic Landforms
Vocab/Misc.
100
At what point does magma become lava?
When it exits a volcano and reaches Earth's surface.
100
Describe what a magma chamber is.
The area below a volcano where magma collects.
100
A volcano that forms from quiet eruptions is a...
Shield volcano
100
Two plates moving away from each other are known as...
Diverging Plate Boundaries
200
What is a hot spot?
A hot spot is an area where material from deep within Earth's mantle rises through the crust and melts to form magma. This can create volcanoes when the magma from the hot spot breaks through Earth's surface.
200
Describe the difference between a volcanic pipe and a volcanic vent.
A volcanic pipe is where magma moves upwards through a long tube that extends from Earth's crust to the magma chamber. A volcanic vent is where lava and gases escape through an opening through Earth's crust.
200
A volcanic neck is formed when...
A volcanic neck is formed when magma hardens in a volcanoes pipe and the surrounding rock later wears away.
200
A mixture of materials can form a fast moving cloud of dangerous substances known as...
Pyroclastic Flow
300
Explain hoe diverging plate boundaries can create a volcano.
Volcanoes can form along the mid-ocean ridges, where two plates move apart. Along the rift valley, lava pours out out of the cracks in the ocean floor. This process gradually builds new mountains.
300
Describe how a volcanic eruption can occur.
During an eruption, magma rises through the pipe, towards the surface. When this happens, the pressure on the gasses in the magma decreases. This causes the bubbles in the gasses to expand. These expanding gasses exert great force and will cause the magma to escape with force.
300
Describe a cinder-cone volcano.
Cinder-cone volcanoes form from explosive eruptions. Their magma is high in silica. They steep-sided but not very tall volcanoes.
300
A long chain of islands that forms along a subduction zone is called a(n)....
Island Arc
400
Why is the Ring of Fire so active?
The Ring of Fire is found along the edge of the Pacific Plate which is very large and is connected to many other plates. Each time these plates shift, volcanoes and earthquakes can occur.
400
Explain the role of silica in a volcanic eruption.
Magma with low silica will be very thin and runny. Magma with high silica will be very thick and can cause explosive eruptions.
400
Describe how a lava plateau forms.
Lava can flow out of large cracks in an area. The thin, runny lava floods an area, cools and hardens. After millions of years, repeated floods of lava can form high, level plateaus.
400
A fast-moving, extremely hot, low silica magma forms into what kind of rock?
Pahoehoe
500
Describe how converging plates create volcanoes.
When plates collide, subduction can occur. The denser plate is forced downwards where it will eventually melt, becoming magma. This magma is filled with gases and when its heated and placed under pressure, the magma will rise creating a volcano.
500
Describe the three three stages of volcanic activity.
Active: A volcano currently erupting or one that will in the very short future. Dormant: A sleeping volcano; one that has not erupted in a long time but may in the future. Extinct: A volcano that is considered dead and one that won't erupt again.
500
Describe composite volcanoes.
Composite volcanoes are tall, cone-shaped mountains in which layers of ash, cinders and bombs layer on top of each other. The silica content in composite volcanoes varies which causes both explosive eruptions and quiet eruptions to occur over a long period of time.
500
A bowl-shaped area that forms at the top of a volcano is a...
Crater