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Volcano
A volcano is a place on the Earth's surface (or any other planet's or
moon's surface) where molten rock, gases and pyroclastic debris erupt
through the earth's crust. Volcanoes vary quite a bit in their structure some are cracks in the earth's crust where lava erupts, and some are
domes, shields, or mountain-like structures with a crater at the summit.
Magma is molten rock within the Earth's crust. When magma erupts
through the earth's surface it is called lava. Lava can be thick and slowmoving or thin and fast-moving. Rock also comes from volcanoes in
other forms, including ash (finely powdered rock that looks like dark
smoke coming from the volcano), cinders (bits of fragmented lava), and
pumice (light-weight rock that is full of air bubbles and is formed in
explosive volcanic eruptions - this type of rock can float on water).
Volcanic eruptions can cause great damage and the loss of life and
property.
The Word Volcano:
The word volcano comes from the Roman god of fire, Vulcan. Vulcan
was said to have had a forge (a place to melt and shape iron) on
Vulcano, an active volcano on the Lipari Islands in Italy.
Extreme Volcanoes:
The largest volcano on Earth is Hawaii's Mauna Loa. Mauna Loa is
about 6 miles (10 km) tall from the sea floor to its summit (it rises about
4 km above sea level). It also has the greatest volume of any volcano,
10,200 cubic miles (42,500 cubic kilometers). The most active volcano
in the continental USA is Mt. St. Helens (located in western Washington
state).
The largest volcano in our Solar System is perhaps Olympus Mons on
the planet Mars. This enormous volcano is 17 miles (27 km) tall and
over 320 miles (520 km) across.
Label the Volcano Diagram
Read the definitions, then label the diagram below.
Definitions
ash cloud - an ash cloud is the cloud of ash
that forms in the air after some volcanic
eruptions.
magma chamber - a magma chamber contains
magma (molten rock) deep within the Earth's
crust.
conduit - a conduit is a passage through which side vent - a side vent is a vent in the side of a
magma (molten rock) flows in a volcano.
volcano.
crust - the crust is Earth's outermost, rocky
layer.
lava - lava is molten rock; it usually comes out
of erupting volcanoes.
vent - a vent is an opening in the Earth's surface
through which volcanic materials erupt.
Types of Volcanoes
There are many types of volcanoes:
Shield Volcano - A gently-sloping volcano that emits mostly basaltic lava (very fluid lava) that
flows in long-lasting, relatively gentle eruptions - explosions are minimal. Shield volcanoes can
be very big. An example is Mt. Kilauea (in Hawaii, USA).
Composite or Strato Volcano - A steep-coned volcano that explosively emits gases, ash,
pumice, and a small amount of stiff, silica lava (called rhyolite). This type of volcano can have
eruptions accompanied by lahars -- deadly mudflows. Most volcanoes on Earth are of this type.
Stratovolcanoes kill more people than any other type of volcanoes - this is because of their
abundance on Earth and their powerful mudflows. Examples are Krakatoa in Indonesia, Mt.
Pinatubo in the Philippines, and Mt. St. Helens in Washington state, USA.
Lava Dome - A bulbous (rounded) volcano that forms when very viscous lava barely flows. An
example is Mont Pelée in Martinique.
Cinder Cone - A cone-shaped volcano whose steep sides are formed by loose, fragmented
cinders that fall to the Earth close to the vent. The lava flows through a single vent that is usually
only up to about 1,000 feet tall. There is usually a bowl-shaped crater at the top. As the gas-filled
lava erupts into the air, the lava fragments into pieces and forms cinders.
Rhyolite Caldera Complex - these are the most explosive volcanoes. They do not look like
common volcanoes -- after an eruption, the result is a caldera (crater) caused when the area
around the vent collapses. Examples are Yellowstone in Wyoming, USA and Lake Taupo in
New Zealand (which erupted around A.D. 80).
Volcano
Fill in the blanks below using words from the word
bank.
Word Bank:
Mars
summit
crust
rock
crater
lava
miles
cracks
Magma
Earth
volcano
erupts
1. A volcano is a place on the Earth's surface (or any other
planet's or moon's surface) where molten
_______________________, gases and pyroclastic debris
erupt through the earth's _______________________.
Volcanoes vary quite a bit in their structure - some are
_______________________ in the earth's crust where lava
erupts, and some are domes, shields, or mountain-like
structures with a _______________________ (a circular
depression) at the summit.
2. _______________________ is molten rock within the Earth's
crust. When magma _______________________ through the
earth's surface it is called _______________________.
3. The largest volcano on _______________________ is
Hawaii's Mauna Loa. Mauna Loa is about 6 miles (10 km) tall
from the sea floor to its _______________________ (it rises
about 4 km above sea level). It also has the greatest volume of
any volcano on Earth, 10,200 cubic miles (42,500 cubic
kilometers).
4. The largest _______________________ in our Solar System
is perhaps Olympus Mons on the planet
_____________________. This enormous volcano is 17
_____________________ (27 km) tall and over 320 miles
(520 km) across.