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What is a Volcano?

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Title: Slide 1 Author: Cobb County School District Last modified by: Christopher Whiting Created Date: 10/1/2006 2:43:14 AM Document presentation format – PowerPoint PPT presentation

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Title: What is a Volcano?


1
What is a Volcano?
  • Volcano-A weak spot in the crust where molten
    material comes to the surface.

2
Volcano locations
  • Ring of fire-Major volcanic belt around the
    Pacific Ocean. (plate boundary)

3
Island Arc-A ring of islands that forms over a
plate boundary.
4
Hot spot-An area where a volcano forms in the
middle of a continental or oceanic plate when
magma melts through the crust like a blowtorch.
5
Types of Volcanoes
  • Composite explosive eruptions that release huge
    amounts of gas and ash. pyroclastic flows and
    lahars can occur. Can produce dust bombs and
    blocks. This type is found on continental-oceanic
    plate boundaries. (ie. Mt. Rainer, Mt. St.
    Helens, Mt. Hood)

6
Shield mainly lava flows (ie. Mt. Kilauea)
7
Cinder Cone bombs, ash, and cinder are ejected
from a volcanic vent and produce a cone.. (ie
Sunset Crater, Arizona)
8
Types of Eruptions
  • Type of eruption is determined by the type of
    magma in the volcano
  • Quiet Eruptions basaltic-thin, runny lava.

9
Explosive Eruptions
  • granitic-thick, sticky lava. (It gets stuck,
    pressure is built, and it explodes)

10
Activity of Volcanoes
  • Active is erupting or has shown signs that it
    may erupt in the near future.

11
Dormant is sleeping, but scientists expect it
to awaken in the future.
12
Extinct unlikely to erupt again.
13
Structure of a Volcano
  • Magma-Extremely hot molten material that also
    includes dissolved gases and including water
    vapor.
  • Magma Chamber-A large underground pocket formed
    as magma rises toward the surface.

14
  • Pipe-A narrow almost vertical crack in the crust
    through which magma rises to the surface.
  • Vent-Point on the surface where magma leaves the
    volcanos pipe.

15
  • Side Vent-When magma forces its way out a volcano
    through the side.
  • Crater-A bowl shaped area that forms around the
    volcanos vent.

16
  • Lava-Magma that reaches the surface.
  • Lava Flow-The river of lava that pours down a
    volcano and over the land.

17
What comes out of a volcano?
  • Gases-Carbon Dioxide and Sulfur Dioxide are
    common gases. Steam also comes out.

18
Lava-What magma is called when it reaches the
Earths surface and loses some of its gas.
19
  • Aa-Cool, slow moving lava.
  • Pahoehoe-Hot, fast moving lava.

20
Blocks-Have sharp corners, are chunks of rock
blown out from inside the volcano.
21
Bombs-Masses of lava that cool into rounded
shapes before hitting the ground.
22
Cinder-When lava is blown into the air during an
eruption, it sometimes cools into small, rough
pieces of rock that are puffed up by gas.
23
Pumice-Formed like cinder, but contains more
trapped gas. Light enough to float on water.
24
Ash-Lava that has been blown apart by gases into
sand-like particles.Dust-The smallest particles
of ash
25
Tuff-When ash mixes with rain or other moisture
and forms a hard, cement-like rock.
26
Lahar-A hot or cold mixture of water and rock
fragments flowing down the slopes of a volcano or
river valley.
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Pyroclastic Flow-A high density cloud that is
mixture of hot, dry rock fragments and gas moving
away from the vent at high speeds. Temperature
is between 200?C to 700?C.
29
Volcanic Landforms
  • Dome Mtn. magma is trapped below a horizontal
    layer and pushes it into a dome shape and cools.

30
Sill magma cools horizontally between rock
layers
31
Dike magma cools vertically btwn. rock layers
32
Volcanic Neck - formed when magma cools in a
volcanic pipe.
33
Lava plateau high level area formed by thin,
running lava.
34
Batholith mass of rock formed when a large mass
of magma cools below the surface.
35
Caldera huge hole left by the collapse of a
huge volcano.
36
Volcanoes in Space
  • Mars-Has the largest volcano called Olympus Mons.
    Around the base of the volcano is a cliff that
    equals 5 times the size of the Grand Canyon.

37
Volcanoes in SpaceVenusHas the most volcanoes
38
Moon
  • Craters are NOT from volcanoes. They are from
    meteorites smashing into the moon. Lava flows
    more than 3 billion years ago created smooth dark
    areas on the moon.

39
THE END????
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Sept 2006
43
14 October 2004
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http//vulcan.wr.usgs.gov/Outreach/AboutVolcanoes/
framework.html
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