Download Chapter 10 Volcanoes and other Igneous Activity Section 10.1

Chapter 10 Volcanoes and other Igneous Activity
Section 10.1 Volcanoes and Plate Tectonics
Origin of Magma
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____________________________ forms in the crust and upper mantle when solid
rock partially melts. The formation of magma depends on several factors,
including heat, pressure, and water content.
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________________________________ – occurs when rock rises and melts due to
reduced pressure.
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_________________________________ – “wet” rock melts faster than “dry” rock
Volcanoes and Plate Boundaries
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Most volcanoes form along ______________________________ and
___________________________ plate boundaries. Some volcanoes form far from
plate boundaries above ________________________ in the crust.
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__________________________________________ – as plates pull apart magma rises to
fill the gap in rift valleys. Most are found at mid-ocean ridges, but some are
found on the continents. The Great Rift Valley in Africa is an example
Volcanoes and Plate Boundaries - Convergent
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_____________________________________________ – occurs where plates collide and
one plate subducts (goes under) another plate. There are 2 types.
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1. ______________________________________________________________________ – the
oceanic crust is more dense and __________________________ underneath the
continent. This creates an ocean trench and a subduction zone. As the
oceanic crust melts back into the mantle, magma rises creating inland
volcanoes on the continent. The Cascades of California, Oregon, and
Washington are and example.
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______________________________________ -the area on Earth that has the most
earthquakes and volcanoes. It is an area of subducting plate boundaries,
where the Pacific Plate is moving under the neighboring continental and
oceanic plates. The Cascade Mountain Range of the Western United States
is a part of the Ring of Fire.
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2. ___________________________________________________ with another oceanic
crust. One plate will be denser than the other and subduct beneath. This
creates a very deep __________________________________, and when the plate
melts back into the mantle magma raises upward and creates an island arc
of volcanoes. The Aleutian Islands of Alaska are an example.
Intraplate Volcanism: Hot Spots
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__________________________________ – weak area of the Earth’s crust within a
plate that allows magma to come to the surface in the form of a mantle
plume. Examples in the United States include the Hawaiian Island chain
and Yellowstone National Park.
Section 10.2 The Nature of Volcanic Eruptions
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The primary factors that determine whether a volcano erupts explosively or
quietly include characteristics of the _________________________ and the amount
of ____________________________ in the magma.
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_______________________________ – the substance’s resistance to flow; whether
the magma is thick and sticky or thin and runny. The more silica in magma
the greater the viscosity = _____________________.
Factors Affecting Eruptions: Viscosity
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____________________________________ are very viscous (thick) because of their
high silica content. They trap gases inside. This makes them erupt
violently. Mostly found on the continents.
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____________________________________ are less viscous (thin) because of low
silica content. They allow gas to be released easily. This allows them to
erupt quietly. Mostly found in the oceans.
Volcanic Material
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Depending on the type of eruption, volcanoes may produce lava flows or
eject pyroclastic materials, or both. All volcanic eruptions also emit large
amounts of gases.
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_______________________________– Basaltic lavas flow faster than Granitic lavas
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________________________________ – faster moving basaltic lava that wrinkles and
looks like twisted ropes
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__________________________________ – Slower moving basaltic lava that forms a
surface of rough, jagged blocks.
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Volcanoes release tremendous amounts of __________________________ into the
atmosphere. These gases include water vapor, carbon dioxide, nitrogen,
sulfur, chlorine, hydrogen, and argon.
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Particles produced in volcanic eruptions are called __________________________.
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___________________________ – fine dust and ash carried by the wind (less than
2mm)
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____________________________ – cinders; small particles that range in size from
small beads to walnuts. (2-64mm)
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____________________________ – Larger than 64mm and made of hardened lava.
They can be as large as houses.
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_____________________________ – Glowing lava that is ejected during the
eruption. The outside crusts over in the air and they splatter when they
make impact.
Volcanoes
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________________________ – opening through which lava flows out.
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________________________ – repeated eruptions eventually build up a mountain.
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________________________ – steep-walled depression at the top of the volcano,
which contains the vent.
Types of Volcanoes
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__________________________________ – made of alternating basaltic lava flows.
They are broad, gently sloping, tall, slightly domed structures. Ex. Hawaiian
Islands
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___________________________________ – made of loose pyroclastic material, such
as ash and lapilli. They are relatively small compared to other volcanoes.
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____________________________________ – also called stratovolcanoes. Most
dangerous volcanoes on Earth. Made of both layers of lava and pyroclastic
material. Most are found in the Pacific Ring of Fire. Generate explosive
eruptions due to trapped gases. Mt. Fuji in Japan >>>>>>>
Volcanic Landforms:
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_______________________________ – depression in a volcanic mountain caused by
a collapse of the crater. Crater Lake in Oregon is a caldera caused by the
eruption of Mt. Mazama. Wizard Island is the cone forming in the lake.
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_______________________________ – a landform made of magma that hardened
inside a volcano and was later exposed by weathering and erosion. Ship
Rock, New Mexico and Devils Tower, Wyoming are examples
Volcanic Hazards
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_____________________________
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_____________________________ – superheated volcanic particles and gases
moving hundreds of miles per hour down the slopes of a volcano.
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________________________ – mudflows that happen when water-soaked volcanic
ash and rock slide rapidly downhill. Ice and snow melted by an eruption can
trigger a _______________________________.
Section 10.3 Intrusive Igneous Activity
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_______________________________ – the structures that result from the cooling
and hardening of magma beneath Earth’s surface.
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Types of Plutons:
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____________________
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_____________________
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______________________
________________________________ – a pluton that forms when magma flows
between parallel layers of sedimentary rock.
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___________________________ – also forms between parallel layers of
sedimentary rock. Laccoliths are lens-shaped which pushes up the overlying
rocks. They can make dome mountains.
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___________________________ – a pluton that forms when magma moves into
fractures that cut across rock layers.
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___________________________ – larger than a pluton, a large body of intrusive
igneous rock that has a surface exposure of more than 100 square
kilometers.