The type of magma that often produces a violent eruption can be described as thick due to high ________ content.
What is silica?
100
When lava hardens quickly to form ropy formations, it is called _____.
What is pahoehoe lava?
100
Volcanic dust and ash can remain in the atmosphere for months or years, causing ________ solar reflection and _______ temperatures.
What is increased and lower?
100
Mount St. Helens, in Washington, covered the city of Spokane with tons of ash. Its eruption would most likely be described as explosive, producing ______ material.
What is pyroclastic?
100
a vent or fissure in the Earth's surface through which magma and gases are expelled is called a(n)
Volcano
200
At _________ plate boundaries, tectonic plates move apart.
What is divergent?
200
The theory that helps to explain the causes of both earthquakes and volcanoes is the theory of _____.
What is plate tectonics?
200
Volcanoes are most likely to form here.
What is along plate boundaries?
200
Lava that is very runny probably has a low ______ content.
What is silica?
200
Places on the Earth's surface that are located directly above mantle plumes are called ___.
What are hot spots?
300
built of layers of lava from repeated nonexplosive eruptions
Shield volcanoes
300
Because the temperature of the mantle is relatively constant, ____ usually causes magma to form.
What is decreased pressure?
300
A ________ is formed when magma erupts from long cracks in Earth's crust and spreads evenly over large areas of the Earth's surface.
What is a lava plateau?
300
A _____ forms when a magma chamber, that supplies material to a volcano, empties and its roof collapses, causing the ground to sink and leaving a large circular depression.
What is caldera?
300
A funnel shaped pit that is found at the top of the central vent in most volcanoes.
What is a crater?
400
A volcano that has a steep slope, a narrow base and is made entirely of pyroclastic material.
What is a cinder cone volcano?
400
Volcanoes with gently sloping sides that are built out of layers of runny lava from repeated nonexplosive eruptions.
What is a shield volcano?
400
Pyroclastic material that forms when the gases in stiff magma expand rapidly and the walls of the gas bubbles explode into tiny glass-like slivers
What is volcanic ash?
400
Pyroclastic material that consists of pebble-like bits of magma that become solid before they hit the ground.
What is lapilli?
400
Sometimes referred to as stratovolcanoes, these volcanoes have steep slopes and a broad base.
What is a composite volcano?
500
Eruptions that resemble a nuclear explosion and are characterized by blasting both molten and solid rock from a volcano.
What is an explosive eruption?
500
Largest volcanic material.
What is volcanic blocks?
500
You would expect to find a long chain of volcanoes above hot spots, subducting plates and at _____ boundary.
What is convergent?
500
Lava fountains are ____ eruptions that can spray lava into the air.
What is nonexplosive?
500
Volcanic activity is common along the Mid-Atlantic Ridge. This activity occurs at a _______ boundary.