Where are the major zones of volcanism What are the parts of a volcano How do volcanic landforms differ Copyright McGrawHill Education Volcanoes Review convergent New volcanism hot spot ID: 657245
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Essential QuestionsHow do plate tectonics influence the formation of volcanoes?Where are the major zones of volcanism?What are the parts of a volcano?How do volcanic landforms differ?
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VolcanoesSlide2
Reviewconvergent
New
volcanism
hot spot
flood basalt
fissureconduitventcratercaldera shield volcanocinder conecomposite volcano
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Vocabulary
VolcanoesSlide3
Volcanism
describes all the processes associated with the discharge of magma, hot fluids,
ash and
gases.Slide4
Volcanoes
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Zones of
Volcanism
Most volcanoes form at plate boundaries. The majority form at convergent boundaries and divergent boundaries. Slide5
Volcanoes
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Convergent volcanism
In an
oceanic-continental
subduction zone, the denser oceanic plate slides under the continental plate into the hot mantle. Parts of the mantle above the subducting plate melt and magma rises, eventually leading to the formation of a volcano. Slide6
Volcanoes
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Convergent volcanism
Most volcanoes located on land result from oceanic-continental subduction. These volcanoes are characterized by
explosive eruptions
.
Santiaguito
Dome, GuatemalaSlide7
Volcanoes
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Two
major
belts
The volcanoes associated with convergent plate boundaries form two major belts. The larger belt, the
Circum-Pacific Belt, is also called the Pacific Ring of Fire. The outline of the belt corresponds to the outline of the Pacific Plate.Slide8
Volcanoes
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Two
major
belts
The smaller belt is the Mediterranean Belt. Its general outlines correspond to the boundaries between the Eurasian, African, and Arabian plates. Slide9
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Volcanoes
Divergent volcanism
Eruptions at divergent boundaries tend to be
nonexplosive
. At the divergent boundary on the ocean floor, eruptions often form huge piles of lava called pillow lava.Slide10
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Volcanoes
Hot
spots
Some volcanoes form far from plate boundaries over hot spots.
A
hot spot is an unusually hot area in Earth’s mantle where high-temperature plumes of mantle material rise toward the surface.Slide11
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Volcanoes
Hot
spots
The Hawaiian islands are located over a plume of magma. The hot spot formed by the magma plume remains stationary while the Pacific Plate slowly moves northwest. Slide12
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Volcanoes
Hot
spots
The volcanoes on the oldest Hawaiian island, Kauai, are inactive because the island no longer sits above the stationary hot spot. The world’s most active volcano, Kilauea, on the Big Island of Hawaii, is currently located over the hot spot.Slide13
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Volcanoes
Hot
spots
Chains of volcanoes that form over stationary hot spots provide information about plate motions. The rate and direction of plate motion can be calculated from the positions of these volcanoes.Slide14
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Volcanoes
Hot
spots
The Hawaiian islands are at one end of the Hawaiian-Emperor volcanic chain. The oldest seamount, Meiji, is at the other end of the chain and is about 80 million years old.Slide15
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Volcanoes
Hot
spots
Flood basalts
form when lava flows out of long cracks in Earth’s
crust. These cracks are called fissures.The Columbia River basalts, located in the northwestern United States, were formed this way. Slide16
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Volcanoes
Hot
spots
About 65
mya
in India, a huge flood basalt eruption created an enormous plateau called the Deccan Traps. The volume of basalt in the Deccan Traps is estimated to be about 512,000 km3.Slide17
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Volcanoes
Anatomy of a Volcano
Lava reaches the surface by traveling through a
tubelike
structure called a
conduit. The lava then emerges through an opening called a vent.Slide18
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Volcanoes
Anatomy of a Volcano
Over time, layers of solidified lava can accumulate to form a mountain known as a volcano. At the top of a volcano, around the vent, is a bowl-shaped depression called a
crater
.
Volcanic craters are usually less than 1 km in diameter. Larger depressions, called calderas, can be up to 100 km in diameter.Slide19
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Volcanoes
Types of Volcanoes
The appearance of a volcano depends on two factors: the
type of material
that forms the volcano and the
type of eruptions that occur.Slide20
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Volcanoes
Shield volcanoes
A
shield volcano
is a mountain with broad, gently sloping sides and a nearly circular base.
Shield volcanoes form when layers of lava accumulate during nonexplosive eruptions. They are the largest type of volcano.Slide21
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Volcanoes
Cinder
cones
When eruptions eject small pieces of lava into the air,
cinder cones
form as this material, called tephra, falls back to Earth and piles up around the vent.Cinder cones have steep sides and are the smallest type of volcano.Slide22
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Volcanoes
Composite
volcanoes
Composite volcanoes
are formed of layers of ash and hardened chunks of lava from violent eruptions alternating with layers of lava that oozed downslope before solidifying.
These volcanoes are generally cone-shaped with concave slopes.Slide23Slide24Slide25
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ReviewEssential QuestionsHow do plate tectonics influence the formation of volcanoes?Where are the major zones of volcanism?
What are the parts of a volcano?How do volcanic landforms differ?
Vocabulary
volcanism
hot spotflood basaltfissureconduitventcratercaldera
Volcanoes
shield volcanocinder conecomposite volcano