Download Chapter 7 Notes: Volcanoes Volcanoes and Plate Tectonics Volcano Magma

Volcanoes and Plate Tectonics
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Chapter 7 Notes: Volcanoes
Volcano: a weak spot in the _______________ where molten material or _______________ comes
to the surface
Magma: a molten mixture of ________ forming substances, ________ and H2O from the mantle
Volcanic Belts: Form along the Earth’s _______________ boundaries
o The boundaries _______________ or Diverge
 Divergent Boundary: Plates move _______________
 Ex: Sea Floor _______________
o Rift _______________
 _______________ pours out and volcano formed
 Convergent Boundary: plates _______________
 Subduction at _______________
o The Crust _______________ and magma can reach the surface
 The denser plate is _______________ and melts to form magma
 The magma ____________ and breaks through the crust to form volcanoes
Places with many Volcanoes
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Ring of Fire: major _______________ belt
o Formed by many volcanoes that rim the _______________ Ocean
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Island Arc: string of _______________ created by volcanoes
o Follow the _______________ of the Trench
o Examples
 _______________
 _______________ Zealand
 Aleutian _______________
 _______________ Islands
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Hot Spots: An area where deep inside the _______________ rises and melts
o Volcanoes form _______________ a hotspot when magma erupts through the crust and
reaches the surface.
o Found…
 Near _______________ boundaries
 In the _______________ of plates
 _______________ the continents
 Ex: old faithful in Yellowstone national park
Properties of Magma
General Properties
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Element: substance that _______________ be broken down into another substance
Compound: substance made of 2 or more _______________
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Physical Property: any characteristic of a substance that can be _______________ or
_______________ without changing the composition of the substance
o Examples: _______________ and melting point
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Chemical Property: any property that produces a _______________ in the chemical
composition of the matter.
o Examples: Ability to _______________
Magma’s Viscosity
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Viscosity: the _______________ of a liquid to _______________
o Depends on the _______________ content
 _______________ silica: Higher viscosity
 When lava cools it form rock rhyolite which is like _______________
 _______________ Silica: Lower viscosity
 Flows _______________ , lava cools to form _______________
o Depends on _______________
 Hot magma flows _______________
 Temperature _______________ produces 2 kinds of lava
o Pahoehoe- fast, hot _______________
o ______________ viscosity
o Looks like: _______________ or coils of rope
 Aa: slow, “_______________ ” lava
o _______________ viscosity
o Looks: _______________ : jagged chunks
Volcanic Eruptions
Pele’s Hair: type of rock formed by hardened lava
____________
Inside a volcano
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Magma _______________ in the magma chamber
Magma then _______________ upward to the vent
Parts of a Volcano
o Pipe: a long _______________ in the ground
that connects the magma chamber to the
surface of the Earth.
o Lava Flow: an area covered by _______________ as it flows out of a side vent
o Crater: a _______________ shaped area that may form at the _______________ of the
volcano around the central vent
Erupting Volcanoes
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How it erupts: Gases that are dissolved in the magma _______________ as the magma goes up
the pipe pushing it upwards until it reaches the top
Two _______________ of volcanic Eruptions
o _______________ Eruptions
 _______________ viscosity magma
 _______________ out of vents
 Can _______________ both kinds of lava
 Ex: Kilauea
o _______________ Eruptions
 _______________ Viscosity magma
After Eruption:
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Lava _______________ into fragments and cools quickly
Lava _______________ into different sizes
o Small:
_______________ Ash
 Fine rocky
o Medium: _______________
 Pebble
o Large:
_______________
 Larger (baseball)
Pyroclastic Flow: occurs during an _______________ when hot gases, ash, cinders and bombs
are expelled
Types of Rock Created
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Obsidian: rock from lava that has _______________ rapidly
o _______________ Texture
Pumice: forms when gas _______________ get trapped in fast cooling lava
Volcanic hazards
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_______________ : quiet eruption can cover a large area
Clouds of deadly _______________
_______________
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Ash: can _______________ entire towns
o _______________ collapse
o Jet planes _______________
o Avalanche, _______________ and mud flows
Stages of Volcanic activity
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Active Volcano: a volcano that is _______________ or shows signs of erupting soon
Dormant Volcano: a _______________ volcano
o It can _______________ in the future
Extinct Volcano: a volcano that is _______________ to erupt again
Monitoring Volcanoes
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Different instruments are used to measure…
o The _______________ of ground H2O
o _______________ around the volcano
o Gases _______________
Volcanic Landforms
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Shield Volcano
o _______________ Eruptions
o Gentle, _______________ mountain
o Ex: Hawaiian islands are shield volcanoes that arise from hot springs
Cinder Cone Volcano
o _______________ , Ash & Bombs erupt
o Explosively forms _______________ shaped hill
Composite Volcano
o Alternate _______________ and explosive eruptions
o Tall _______________ shaped mountains
Lava Plateau
o Lava _______________ out of cracks
o Thin, _______________ lava
o Ex: Columbian Plateau in Washington, Oregon, & Idaho
Calderas
o Not the same as _______________
o This is a _______________ hole left by the collapse of a volcanic mountain
Land near a volcano
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Soil is Very _______________
o Contains _______________ , phosphorus, and other substances
Landforms from magma
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Sometimes magma ________ through cracks in the upper crust but doesn’t reach the surface
Five different kinds
o Volcanic Necks: magma hardens in the _______________
o Dikes: magma hardens across _______________ layers
o Sills: magma hardens between _______________ layers of rock
o Batholith: large amount of magma _______________ in the crust
o Domed Mountain: magma forces the layers of rock to bend _______________
Geothermal Activity
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Magma that is only a few kilometers beneath the surface _______________ the ground water
Occurs in an area of present or past _______________ activity
o Hot _______________
o _______________