What Causes Volcanoes?
What Causes Volcanoes II?
Types of Volcanoes
Types of Volcanoes II
Igneous Rock Features
100
A ___________ is an opening on Earth's surface that magma flows out of.
vent
100
What is the most active volcano on Earth?
The most active volcano on Earth is Kilauea in Hawaii.
100
What is silica?
Silica is a compound made of silicon and oxygen.
100
Mt. St. Helens in Washington is an example of what type of volcano?
Composite volcano
100
How are batholiths formed?
Batholiths are formed when magma cools underground before reaching the surface.
200
Why does Iceland have volcanoes?
Iceland has volcanoes because it sits on the Mid-Atlantic Ridge where Earth's plates are moving apart.
200
An opening in Earth's surface that forms a mountain when layers of lava and volcanic ash erupt and build up is called a __________________.
volcano
200
If a volcano has magma with a lot of silica in it, what type of eruption will it have, and explain why.
Magma that has a lot of silica in it is thick and traps gas causing pressure to build and explosive eruptions.
200
Bits of rock or solidified lava that drop from the air in a volcanic eruption is called ________________.
tephra
200
A large opening produced when the top of a volcano collapses down is called a ________________.
caldera
300
What are three ways volcanoes can occur?
1) plates moving apart 2) plates moving together 3) at hot spots
300
Soufriere Hills volcano in Montserrat is an example of a volcano formed by: A) Plates moving apart B) Plates moving together C) Plates moving over a hot spot
B) Plates moving together.
300
What controls whether an eruption will be explosive or quiet?
1) the amount of water vapor and other gases trapped in the magma 2) how much silica is present in the magma
300
What are the three forms/types of volcanoes?
1) shield volcanoes 2) cinder cone volcanoes 3) composite volcanoes
300
Crater Lake is and example of a _____________.
caldera
400
How do hot spots form islands and volcanoes?
The plate moves over a hot-spot and magma rises toward Earth's surface. Magma melts through the crust forming volcanoes. If the volcano rises above the water, it forms an island.
400
Explain what happens when plates move apart and form volcanoes.
When plates move apart, long deep cracks are formed called rifts. Magma flows out of the rifts and cools on the seafloor.
400
Explain how trapped gases affect the volcanic eruption. What would cause a quiet eruption and what would cause an explosive eruption?
Gases get trapped in magma by the pressure of surrounding magma and rock. As the magma nears the surface, there is less pressure which allows the gas to escape from the magma. Quiet = gas escapes easily from magma Explosive = gas builds up to high pressures and eventually erupts
400
Explain how composite volcanoes are formed.
Composite volcanoes are formed when Earth's plates come together and one plate is forced below the other plate. The heat inside the Earth then heats up the bottom plate creating magma that rises and erupts from the volcano.
400
Compare and contrast sill and dikes.
In both sill and dikes, magma squeezes through cracks in rock and hardens. In a sill the cracks are horizontal (sideways), and in dikes, the cracks are vertical (up and down).
500
Describe what happens when plates move together and form a volcano.
The heavier plate is forced under the lighter plate. Magma forms when the heavier plate gets deep enough and hot enough to melt. Magma is forced to the surface causing volcanoes.
500
Explain how volcanoes are formed.
Deep inside Earth heat & pressure cause rock to melt and form magma. The magma is less dense (lighter) than the rock around it, so it is forced upward toward Earth's surface. Magma then flows out through an opening called a vent. As the lava flows out, it cools quickly and becomes solid forming layers around the vent.
500
Explain what a composite volcano is.
When a volcano switches between loud explosions and quiet eruptions. During the loud explosive eruption tephra shoots out of the volcano and lands on the sides. During the quiet eruptions, lava slowly oozes out of the volcano. The lava and tephra form alternating layers on the outside of the volcano.
500
What is the difference between a shield volcano and a cinder cone volcano?
In a shield volcano, silica poor lava flows out in flat layers. The layers build up and form broad gently sloping sides. In a cinder cone volcano, explosive eruptions throw lava and rock high into the air. The lava and rock falls to the ground forming a steep-sided, loosely packed volcano.
500
What is a volcanic neck and how does it form?
A volcanic neck is solid igneous core in the vent of a volcano. It is formed when a volcano stops erupting the magma hardens inside the vent. Erosion begins to wear away the volcano leaving behind the solid igneous core.
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