Volcanoes

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Volcanoes
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Introduction
Volcanoes occur along the earth's tectonic plates
where molten rock is forced upward from magma
reservoirs deep in the earth. The magma may be
fifty to one hundred miles below the ground. As
the magma rises, it gives off gases that cause an
explosion in the vents of the volcano. Lava can
reach temperatures of over 2000 degrees F. Molten
rock, dust, and gases push through the opening in
the earth's crust and form a mountain. A violent
explosion can cause the top of the volcano to
blow off leaving a deep crater.
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Fissure

• A fissure is a crack in the ground that lava
  comes out of.
• Sometimes when lava cools is goes back into the
  fissure where it came from.
• Fissures can also erupt for a period of hours or
  days.

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Vents

• Vents are openings in the earth where magma and
  gases pour into the ground or the atmosphere.
• Vents may have a circular-shaped structure,or a
  tiny ground crack.

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Ash

• Volcanic ash is not like other ash because it is
  hard and doesnt dissolve in water.
• Ash is very small and is made of rock, minerals,
  and volcanic glass pieces.
• Ash is created when a volcano erupts and magma
  splits in small pieces.
• Hot ash and gas form a cylinder above the volcano
  and creates a gray cloud.

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Magma

• Magma is molten rock underneath the earth.
• Magma collects inside the magma chamber before
  the volcano erupts.
• Magma consists of a a liquid portion(melt) and a
  solid portion made of minerals(crystallized from
  the melt).
• When the volcano erupts onto the earths surface,
  the magma becomes a liquid.

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Caldera

• A caldera is a big, circular depression at the
  top of a volcano.
• A caldera is formed when magma is disputed, or
  erupted, from the vent.
• Calderas are different from craters, which are
  smaller.
• The removal of large volumes of magma may result
  in the loss of structural support, causing the
  caldera to form after the explosive excavation of
  rocks.
• Caldera is the Spanish word for caldron.

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Lava

• Lava is molten rock that reaches the earths
  surface through a volcano or fissure.
• Magma becomes lava when it reaches the earths
  surface
• All magma and lava consist mainly of a liquid,
  along with solid rock and gaseous matter.
• Lava is from the Italian word for stream lavare
  -to wash

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Lava Flow

• Lava flows are masses made of melted rock called
  magma.
• It pours onto Earths crust during an effusive
  eruption.
• Lava flows come in various shapes and sizes as
  all volcanoes are different.
• The viscosity of lava is one hundred thousand
  times that of water.
• The viscous rock can flow many miles before
  cooling.

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Lava Dome

• A lava dome is a round, steep-sided mound created
  by the eruption of high-silica lava.
• Lava domes stick to the side of volcanoes before
  cooling.
• The dome may include one or more lava flows.
• Domes may reach heights of several hundred
  meters, and they can grow slowly and steadily
  grow for months or years.

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Volcanic Eruptions