Download Volcanos

What is a volcano?
A Volcano is an opening at the crust of the earth in which molten rock called magma
and gases can escape to the surface. This is a photo of the Volcano Paricutin (Pear – a
– cu –teen).
The Earth’s Layers
The Earth is made up of 4 different layers. The Inner Core, the Outer Core, The Mantle
(upper and lower) and the Crust.
The Crust is the layer that we live on. The Mantles are much hotter and have the ability
to flow. The Core is hotter still with pressures so great that you would be squeezed into a
ball as small as a marble if you ever went to the Core. Ouch!
The Crust
The Earth’s crust is like the skin of an apple. It is very thin compared to the
other layers. The crust of the Earth is broken into several pieces called
plates. The plates float on the soft Mantle below the crust.
Volcanos
The Plates
There are twelve main plates on the Earth’s surface. The red lines
represent the largest plate boundaries. A plate boundary occurs
when two plates come together. The plates move in a very slow
but constant motion. They move between 1 cm and 10 cm each
year. This does not seem like much but over millions of years it
adds up to great distances of movement!
How do volcanoes form?
There are three different ways that volcanoes can form.
1. Subduction Zone Volcanoes – form at the boundary of two plates
2. Mid-ocean rift Volcanoes – form when two oceanic plates are spreading apart.
3. Hot Spot Volcanoes – form by melting magna.
How do they become mountains?
Volcanoes build themselves up into mountains with repeated eruptions. Here is a
photo of how the Volcano Paricutin built itself up over nine years of constant
eruptions.
Classifying Volcanoes
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Volcanoes can be classified as active, dormant or extinct.
Active volcanoes are either erupting or have erupted in recorded history. There are
over 500 active volcanoes on the earth today.
Dormant volcanoes are resting volcanoes that are likely to erupt in the future.
Extinct volcanoes can be called dead volcanoes because they have not erupted in
recorded history and are not expected to erupt again.
Mt. St. Helens had been dormant for 123 years before it erupted in 1980.
When will they erupt?
Predicting when a volcano will erupt is next to impossible. Geologists are becoming
better at recognising signs that a volcano will erupt soon. Signs can be small
earthquakes occurring near the volcano. Magma moving higher and higher inside
the mountain. Scientists cannot stop a volcano from erupting but they can warn
and evacuate people away from the volcano zone.
Scientist measuring an earthquake near the opening of Mt. St. Helens.
What you need to know!
This is a model of the inside and the
outside of an erupting volcano. The
letters represent different parts of
the volcano that you need to know.
A – Magma Chamber, located
beneath the earths surface.
B – Dike, magma that cuts through
the layers of rock.
C – Side vent, when magma reaches
the surface it is called lava. A side
vent is another way for the lava to
escape.
Side Vent
What you need to know!
D – Conduit, the main tube or pathway
for magma.
E – Crater and Main Vent, bowl shaped
opening for the lava to escape
F – Tuff, lava and ash that runs down the
mountain when the volcano erupts.
The crater of a volcano.
10 most famous Volcanos
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Mt. Mazama, Ore. (lost its top in series of eruptions about 7,000 years ago, eventually forming Crater
Lake)
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Mt. Vesuvius, Italy (buried Pompeii in AD 79)
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Mt. Fuji, Japan (picturesque symbol of Japan; last erupted in 1707)
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Mt. Tambora, Indonesia (1815 eruption caused "a year without summer" in 1816)
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Llullaillaco, Argentina-Chile (world's tallest active volcano at 22,109 feet; last erupted in 1877)
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Krakatau, Indonesia (1883 eruption wiped out island, colored sunsets around the world for two years)
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Mt. Pelee, Martinique (only two people in nearby town of 30,000 survived 1902 blast)
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Lassen Peak, Calif. (1917 eruption was last in 48 contiguous states--until Mt. St. Helens)
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Mt. St. Helens, Wash. (1980 eruption killed 57)
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Mauna Loa, Hawaii (world's largest active volcano; last erupted in 1984)