Notes: Volcanoes
Where are volcanoes found on Earth’s surface?
A _________________ is a mountain that forms in Earth’s crust when molten material, or magma reaches the
surface. _________________ is a molten mixture of rock-forming substances, gases, and water from the
mantle. When magma reaches the surface, it is called ______________________. After magma and lava cool,
they form solid rock.
Volcanoes form a regular pattern on Earth. They occur in many great,
long belts. Volcanic belts form along the boundaries of
___________________________. Volcanoes can occur where two plates
pull apart, or diverge. They can also occur where two plates push
together, or converge. The ____________________________ is one
major belt of volcanoes. It includes many volcanoes that rim the Pacific
Ocean.
Volcanoes form along the mid-ocean ridges, where two plates move apart. Along the rift valley, lava pours
out of the cracks in the ocean floor. This process gradually builds new mountains. Volcanoes also form along
diverging plate boundaries on land.
Many volcanoes form near converging plate boundaries where
two oceanic plates collide. The resulting volcanoes sometimes
create a string of islands called an _______________________.
Volcanoes also occur where an oceanic plate is subducted
beneath a continental plate.
A __________________ is an area where material from
deep within Earth’s mantle rises to the crust and melts to
form magma. A volcano forms above a hot spot when
_______________ erupts through the crust and reaches
the surface. Hot spots stay in one place for many millions
of years while the plate moves over them. Some hot spot
volcanoes lie close to plate boundaries. Others lie in the
middle of plates.
What happens when a volcano erupts?
All volcanoes have a pocket of magma beneath the surface, called a ________________________, where the
magma collects. Magma moves upward through a __________________, a long tube that extends from Earth’s
crust up through the top of the volcano, connecting the magma chamber to Earth’s surface. Molten rock and
gas leave the volcano through an opening called a _____________________. A ________________________
is the spread of lava as it pours out of the vent. A _____________________ is bowl-shaped area that may form
at the top of a volcano around the central vent.
During an eruption, dissolved gases trapped in the magma expand, form bubbles, and exert great force. When a
volcano erupts, the force of the expanding gases pushes magma from the ______________________________
through the ____________________ until it flows or explodes out of the _____________________.
___________________________ classify volcanoes as ________________ or __________________. Whether
an eruption is quiet or explosive depends in part on the magma’s ___________________ content and whether
the magma is thin and runny or thick and sticky. ______________________ is a material found in magma that
forms from the elements oxygen and silicon. A volcano erupts quietly if its magma is __________ or
_______________ in silica. The gases in the magma bubble out gently. The lava oozes quietly from the vent
and can flow for many kilometers. Quiet eruptions can produce different types of lava. ___________________
forms from fast moving, hot lava that is thin and runny. ________ forms from lava that is cooler and thicker.
This is slow moving lava. A volcano erupts explosively if its magma is _______________ in silica. Trapped
gases build up pressure until they explode. The erupting gases and steam push the magma out with incredible
force. Both kinds of eruptions can cause damage far from the crater’s rim. A _________________
______________ is a mixture of hot gases, ash, cinders, and bombs that flow down the sides of a volcano when
it erupts explosively.
What are the stages of volcanic activity?
Geologists often use the terms ________________________, _________________________ or
___________________________ to describe a volcano’s stages of activity. An active, or _________________,
volcano is one that is erupting or has signs that it may erupt in the near future. A dormant, or
_________________________, volcano is a volcano that scientists expect to awaken in the future and become
active. An extinct, or ____________________, volcano is a volcano that is unlikely to ever erupt again.
Notes: Volcanoes
Where are volcanoes found on Earth’s surface?
A ___volcano_______ is a mountain that forms in Earth’s crust when molten material, or magma reaches the
surface. _____Magma__(UNDERGROUND)__________ is a molten mixture of rock-forming substances,
gases, and water from the mantle. When magma reaches the surface, it is called _____lava__(ABOVE
GROUND)_______________. After magma and lava cool, they form solid rock.
Volcanoes form a regular pattern on Earth. They occur in many great,
long belts. Volcanic belts form along the boundaries of
____Earth’s plates_________. Volcanoes can occur where two plates
pull apart, or diverge. They can also occur where two plates push
together, or converge. The ____Ring of Fire______________ is one
major belt of volcanoes. It includes many volcanoes that rim the Pacific
Ocean.
Volcanoes form along the mid-ocean ridges, where two plates move apart. Along the rift valley, lava pours
out of the cracks in the ocean floor. This process gradually builds new mountains. Volcanoes also form along
diverging plate boundaries on land.
Many volcanoes form near converging plate boundaries where
two oceanic plates collide. The resulting volcanoes sometimes
create a string of islands called an ___island arc________.
Volcanoes also occur where an oceanic plate is subducted
beneath a continental plate.
A ______hot spot_______ is an area where material from
deep within Earth’s mantle rises to the crust and melts to
form magma. A volcano forms above a hot spot when
___magma______ erupts through the crust and reaches
the surface. Hot spots stay in one place for many millions
of years while the plate moves over them. Some hot spot
volcanoes lie close to plate boundaries. Others lie in the
middle of plates.
What happens when a volcano erupts?
All volcanoes have a pocket of magma beneath the surface, called a ___magma chamber____________, where
the magma collects. Magma moves upward through a ____pipe__________, a long tube that extends from
Earth’s crust up through the top of the volcano, connecting the magma chamber to Earth’s surface. Molten rock
and gas leave the volcano through an opening called a ____vent_______. A ___lava flow_________
is the spread of lava as it pours out of the vent. A ___crater________ is bowl-shaped area that may form at the
top of a volcano around the central vent.
During an eruption, dissolved gases trapped in the magma expand, form bubbles, and exert great force. When a
volcano erupts, the force of the expanding gases pushes magma from the ____magma chamber________
through the ___pipe______ until it flows or explodes out of the __vent___.
___Geologists___________ classify volcanoes as __quiet_______ or ____explosive________. Whether an
eruption is quiet or explosive depends in part on the magma’s ____silica_____ content and whether the magma
is thin and runny or thick and sticky. ____Silica_____________ is a material found in magma that forms from
the elements oxygen and silicon. A volcano erupts quietly if its magma is __hot_____ or ____low_______ in
silica. The gases in the magma bubble out gently. The lava oozes quietly from the vent and can flow for many
kilometers. Quiet eruptions can produce different types of lava. ___Pahoehoe_________ forms from fast
moving, hot lava that is thin and runny. ___Aa___ forms from lava that is cooler and thicker. This is slow
moving lava. A volcano erupts explosively if its magma is ____high_____ in silica. Trapped gases build up
pressure until they explode. The erupting gases and steam push the magma out with incredible force. Both
kinds of eruptions can cause damage far from the crater’s rim. A ____pyroclastic__ __flow____ is a mixture
of hot gases, ash, cinders, and bombs that flow down the sides of a volcano when it erupts explosively.
What are the stages of volcanic activity?
Geologists often use the terms _____active__________, ________dormant________ or
______extinct____________ to describe a volcano’s stages of activity. An active, or ___live______, volcano
is one that is erupting or has signs that it may erupt in the near future. A dormant, or ___sleeping________,
volcano is a volcano that scientists expect to awaken in the future and become active. An extinct, or
_____dead_______, volcano is a volcano that is unlikely to ever erupt again.