What are volcanoes

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Agua, Guatemala

• What are volcanoes?

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• Any movement of magma on or inside the earth is
  called volcanism.
• A volcano includes the vent and the volcanic
  cone.

Mt. Pelee-Martinique Largest of deaths in 1902
in st. Pierre
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Volcanic Cone

• Is the pile of lava, dust, ash, and rock
  particles around the vent.

• The opening from
• which lava flows
• is called a vent.

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Caldera

• When the top of a
• volcano is blown off, or
• the sides fall into the
• vent, a caldera forms.

• Some fill with water
• and form lakes.

Crater Lake-Oregon
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Volcanic Eruptions

• They can be quiet or explosive.
• Different kinds of eruptions form different
  volcanic cones.

Paracutin, Mexico
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3 Types of Volcanoes

• 1 Shield cones- hardened lava coming from quiet
  eruptions.
• - gentle slopes, wide bases (Hawaii)

Mauna Loa- Hawaii (1984)- very active
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2 Cinder Cones

• Made up of rock particles that are thrown out of
  a vent.
• Explosive
• Steep sides,narrow bases
• Not very high
• (Paracutin in Mexico)

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3- Strata Cone

• A combination of rocks particles and lava
• Eruptions can be quiet and explosive
• Usually the most dangerous
• Mt. St. Helens

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Colimo- West of Mexico City, February 5, 2002
evacuated 200 people because of tremors. Very
active!!!
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Diamond Head Crater- Probably the most famous
landmark in Hawaii is Diamond Head, a 1.2 km wide
tuff ring near the southeast end of the Island of
Oahu. Early sailors mistakenly thought glistening
calcite crystals inside the tuff rocks were
diamonds, leading to the incorrect name. During
World War II tunnels were dug in the soft tuff
for look-out posts to warn of possible invasion.
Diamond Head is still military property, but is
open for hikes and drives to scenic views
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Mt.St.Helens after 1980 eruption
2 scientists
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Venus has more volcanoes than any other planet in
the solar system. Over 1600 major volcanoes or
volcanic features are known (see map), and there
are many, many more smaller volcanoes. (No one
has yet counted them all, but the total number
may be over 100,000 or even over 1,000,000).