Transcript Volcano - Simpson

What is a Volcano?
• Volcano-A weak spot in the crust where
molten material comes to the surface.
Volcano locations
• Ring of fire-Major volcanic belt around the
Pacific Ocean. (plate boundary)
Island Arc-A ring of islands that
forms over a plate boundary.
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.
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)
Shield = mainly lava flows; (ie. Mt. Kilauea)
Cinder Cone = bombs, ash, and cinder are
ejected from a volcanic vent and produce a
cone.. (ie Sunset Crater, Arizona)
Types of Eruptions
• Type of eruption is
determined by the
type of magma in the
volcano
• Quiet Eruptions –
basaltic-thin, runny
lava.
Explosive Eruptions–
• granitic-thick,
sticky lava. (It
gets stuck,
pressure is built,
and it explodes)
Activity of Volcanoes
•
Active – is erupting or has shown signs
that it may erupt in the near future.
Dormant – is sleeping, but scientists expect
it to awaken in the future.
Extinct – unlikely to erupt again.
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.
• 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
volcano’s pipe.
• Side Vent-When
magma forces its way
out a volcano through
the side.
• Crater-A bowl shaped
area that forms
around the volcano’s
vent.
• Lava-Magma
that reaches the
surface.
• Lava Flow-The
river of lava that
pours down a
volcano and over
the land.
What comes out of a volcano?
Gases-Carbon Dioxide
and Sulfur Dioxide
are common gases.
Steam also comes
out.
Lava-What magma is called when it reaches
the Earth’s surface and loses some of its
gas.
• Aa-Cool, slow
moving lava.
• Pahoehoe-Hot,
fast moving lava.
Blocks-Have sharp corners, are chunks of
rock blown out from inside the volcano.
Bombs-Masses of lava that cool
into rounded shapes before hitting
the ground.
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.
Pumice-Formed like cinder, but
contains more trapped gas. Light
enough to float on water.
Ash-Lava that has been blown apart by
gases into sand-like particles.
Dust-The smallest particles of ash
Tuff-When ash mixes with rain or
other moisture and forms a hard,
cement-like rock.
Lahar-A hot or cold mixture of water
and rock fragments flowing down the
slopes of a volcano or river valley.
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.
Volcanic Landforms
•
Dome Mtn. – magma is trapped below a
horizontal layer and pushes it into a
dome shape and cools.
Sill – magma cools horizontally
between rock layers
Dike – magma cools vertically
btwn. rock layers
Volcanic Neck - formed when
magma cools in a volcanic pipe.
Lava plateau – high level area
formed by thin, running lava.
Batholith – mass of rock formed
when a large mass of magma cools
below the surface.
Caldera – huge hole left by the
collapse of a huge volcano.
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.
Volcanoes in Space
Venus
Has the most volcanoes
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.
THE END????
http://vulcan.wr.usgs.gov/Outrea
ch/AboutVolcanoes/framework.
html
Sept 2006
14 October 2004
http://vulcan.wr.usgs.gov/Outreach/
AboutVolcanoes/framework.html