Ch 8 Study Guide
Mountains and Volcanoes
I. Movement of rock builds mountains.
A. Most mountains form along plate boundaries.
1. If you were to climb Mount Everest, you would be standing on
_________ containing the remains of ocean ____________.
2. As continental mountains _________, material once at the bottom of an
__________ can be pushed many miles high.
B. Mountain Ranges and Belts
1. A mountain is an area of ________ that rises steeply from the land
around it.
2. Most mountains belong to __________—long lines of mountains that
were formed at about the __________ time and by the same
processes.
3. Ranges that are close together make up mountain ___________.
C. Mountains, Rocks, and Sediment
1. Rocks break down into _________ pieces that can be carried by
__________ or ________. These pieces are called ____________.
2. The land becomes __________ as mountains wear down and
____________ fill with sediments.
D. Mountains can form as rocks fold.
1. A folded mountain is a mountain that forms as ________________
crust crumples and _________ into folds.
2. Folded mountains form as an ___________ plate sinks under the edge
of a ______________ or as continents _____________.
(Use page 257 captions for the next three numbers)
3. Convergent Boundary Develops—Folded mountains formed as
____________ and continental plates pushed together.
4. Continental Collision Begins—Crust along the edges of ________
continents was crumpled and ___________ into mountains.
5. Collision Continues—As the collision continues, the __________
keeps folding. Also, earthquakes are _____________.
E. Mountains can form as rocks move along faults.
1. Mountains that form as blocks of ___________ move _____ or
___________ along normal faults are called ________-_________
mountains.
2. Fault-block mountains form as the lithosphere is ______________ and
__________ apart by forces within Earth. The rocks of the
_________ are cool and rigid. As the lithosphere begins to stretch,
the crust _________ into the faults that separate them.
3. Fault-Block Mountains (see picture on page 259)
a. Fault-block mountains form as the crust ___________ and
__________ into blocks that move along faults.
b. Stretching Begins—The crust __________ into blocks as it is
stretched.
c. Blocks Tilt or Drop Down—As the _________ is stretched
more, the _________ move along the normal faults
between them.
4. Folded mountains are __________ up by slow, continual stress that
causes rock to gradually _______. Fault-block mountains form,
_____________ by earthquake, as stress built up in the _________
is released by the movement of _________.
5. Folded mountains form where continental crust is being ___________,
and fault-block mountains form where it is being _____________.
II. Volcanoes form as molten rock erupts.
A. Volcanoes erupt many types of material.
1. A volcano is an opening in Earth’s ________ through which molten
__________, rock fragments, and hot ________ erupt.
2. The violence of an eruption depends mainly on the type of __________
feeding the volcano.
B. Magma
1. A major portion of all magma is _________, which is a compound of
silicon and ____________.
2. Lava is _______ that has reached Earth’s ___________.
C. Rock Fragments
1. Tiny rock fragments form volcanic ________, which consists of
particles ranging from the size of ___________ to about the size of
_________ grains.
D. Volcanic Gases
1. During an eruption, volcanic gases can mix with rock _____________
and stay near the ___________. The mixture forms a
______________ flow, which is a dense cloud of ____________
gases and _________ fragments that races downhill.
E. Most volcanoes form along plate boundaries.
1. Volcanoes are common along ___________ plate boundaries where
__________ plates sink beneath other plates. As a plate sinks deep
into a ___________ zone, it heats and begins to melt, forming
____________.
2. Volcanoes are also common along ___________ boundaries where
plates _______ apart, allowing magma to rise from the _________.
F. Volcanoes can have many shapes and sizes.
1. Shield Volcano—a shield volcano is shaped like a broad, ________,
dome. It is built up by _________ eruptions of lava that is
relatively _______ in silica and therefore flows ___________ and
spreads out in ________ layers.
2. Cinder Cone—a cinder cone is a _________, cone-shaped hill formed
by the eruption of __________ and other rock fragments that pile
up around a _________ crater. Cinders form as _______-_______
magma erupts. Escaping gases throw _________ chunks of lava
into the air, where they __________ before landing. Cinder cones
are tens to hundreds of meters ______. Many of them form on the
_________ of other types of volcanoes.
3. Composite Volcano—a composite volcano is a cone-shaped volcano
built up of layers of ________ and layers of _________ fragments.
Its magma is high in _________, and therefore is pasty. A
composite volcano is ___________ near the top and flattens out
toward the ___________. Because hardened lava flows add
strength to the structure of a composite volcano, it can grow much
____________ than a cinder cone.
4. Composite volcanoes have ____________ eruptions for two reasons.
First, expanding gases ___________ in rising magma tend to cause
_____________. Second, hardened lava from earlier eruptions
often _________ openings in these volcanoes. This rock must be
_________ out of the way before any more magma can ________.
G. Scientists monitor volcanoes.
1. Scientists study the _______ and _________ of volcanic rocks around
a volcano to understand the volcano’s history, including how much
________ has passed between eruptions and how _________ the
eruptions have been. This information gives ________ about
____________ future eruptions.
2. Warning people to move away from a __________ that is about to
erupt can save ________. Many of the _________ volcanoes that
are closely monitored are located near _________ cities.
III. Volcanoes affect Earth’s land, air, and water.
A. Volcanic eruptions affect the land.
1. Damage can occur _________ from the volcano.
2. But volcanoes _________ as well as destroy.
B. Immediate Effects
1. Lava flows—even a slow-moving lava flow will knock down,
_________, or burn nearly everything in its _________.
2. Volcanic Ash—large amounts of falling ______ can suffocate plants,
animals, and __________.
3. Mudflows—are landslides that occur when loose _________ and
________ are mixed with __________.
4. Pyroclastic flows—as a flow passes, it can leave a thick layer of
volcanic __________ fragments.
5. Landslides—is a rapid ___________ movement of rock and ________.
6. Steam Explosions—occur when magma comes near __________ or
into ___________ with it.
C. Long-term effects
1. Volcanic ___________ can be tremendously destructive. But even
after an eruption _______, a volcano can remain dangerous for
many _________.
2. Highly productive farmland surrounds some _________ volcanoes.
D. Volcanic gases and ash affect the air.
1. Some gases, such as sulfur __________, form acids when they mix
with _________ in the air. These _______ fall to Earth’s surface
in _________, _________, or ___________. Rain that contains
large amounts of _______ is called acid _________. Volcanoes
are sources of acid-forming ___________.
2. Volcanic gases can lift ________ high above en erupting volcano.
___________ can then carry the ________ far away. During the
May 1980 eruption of Mount St. Helens, ash falling 250 miles
away in Spokane, Washington, blocked so much ___________ that
nighttime streetlights were turned on during the ________.
E. Hot Springs, Geysers, and Fumaroles
1. At a type of hot spring called a ___________, water shoots into the air.
A geyser forms where _________ collects in an underground
_____________, then erupts through a narrow channel.
2. A feature known as a fumarole is similar to a _______ ____________.
Instead of liquid water, though, a fumarole releases ____________
and other __________.
F. Deep-Sea Vents
1. Deep-sea vents are hot _________ that form at spreading centers in the
_________. In these places, the ocean floor has many _________
through which cold seawater ________ to depths of several
kilometers. The sea water gets heated by _______ rock and
__________, then rises again. The hot water coming out of the
ocean floor is ________ in dissolved minerals and gases from the
rock and magma.
2. Deep-sea vents support such unusual life forms as ________ crabs and
tubeworms that measure up to 10 feet _________. These animals
feed on ______-celled organisms that get their energy from
___________ in the vent water.