Transcript volcano-notes - Cobb Learning

The Dangers and Benefits of Volcanoes video 9.16
A volcano is a weak spot in the crust where molten material, or
magma, comes to the surface. The landforms that we call
volcanoes are created by repeated eruptions of lava.
Magma is the molten mixture of
rock-forming substances,
gases, and water that makes
up part of Earth's mantle.
video
Most volcanoes occur along diverging plate boundaries, such as the midocean ridge, or in subduction zones around the edges of oceans.
When magma reaches the
surface, it is called lava. After
lava has cooled, it forms solid
rock. The lava released during
volcanic activity builds up Earth's
surface. Volcanic activity is a
constructive force that adds new
rock to existing land and forms
new islands.
video
Volcanic Eruptions
During volcanic eruptions, many rock fragments are blown into the air. The
smallest particles are called volcanic dust. (less than 0.25 mm)
Volcanic Ash ( 0.25 -5mm) falls to the Earth and forms small rocks.
Volcanic bombs (a few cm to several meters) are molten and harden as they travel
through the air.
Parts of a Volcano
pipe - a long tube in the ground that connects the magma chamber to Earth's surface
crust - the crust is Earth's outermost, rocky layer.
lava - lava is molten rock; it usually comes out of erupting volcanoes.
magma chamber - a magma chamber contains magma (molten rock) deep within the Earth's crust.
vent - a vent is an opening in the Earth's surface through which volcanic materials erupt.
caldera - the depression created when the roof of a magma chamber collapses.
Subduction, Magma Chambers
Volcanic Mountains 5.46
Label a Volcano
ash
vent
lava
pipe
crust
magma
chamber
Parts of a Volcano
ash
side vent
vent
lava
pipe
crust
magma chamber
Magma Inside the Earth 4.45
Types of Volcanoes
Different types of volcanic eruptions form different types of volcanoes.
Cinder cones
Shield volcanoes
Composite volcanoes
Types of Volcanoes
Composite
Tall, cone-shaped mountains that are typically
steeply-sided, symmetrical volcanoes in which
layers of lava alternate with layers of ash.
Examples of composite volcanoes include Mount
Fuji in Japan and Mount St. Helens Washington
state.
video
Composite
Mt. Vesuvius
Mount Vesuvius
Images of victims in
eruption of Vesuvius
in 79 AD. Most died
as a result of
suffocation from the
ash.
video
Types of Volcanoes
Cinder Cone
Cinder cone volcanoes are the most common
kind of volcanoes.They are steep sided
cones. Streaming gases carry liquid lava
blobs into the atmosphere that fall back to
earth around a single vent to form the cone.
The volcano forms when ash, cinders and
bombs pile up around the vent to form a
circular or oval cone.
video
Cinder Cone
Types of Volcanoes
At some places on Earth's surface, thin
layers of lava pour out of a vent and
harden on top of previous layers. Such
lava flows gradually build a wide, gently
sloping mountain called a shield volcano.
Shield volcanoes rising from a hot spot
on the ocean floor created the Hawaiian
Islands.
Shield Volcano
video
Shield
Crater/Caldera
There is often a funnel-shaped pit or depression at the top of a volcanic
cone. This pit is called a crater. If the crater becomes very large as a
result of the collapse of its walls, it is called a caldera. A caldera may
also form when the top of a volcano explodes or when the magma
chamber collapses.
Volcanic Crater
Caldera
Volcanic Activity
Volcanoes are rather unpredictable . Some erupt regularly, others have not erupted in
modern history. Scientists classify them as active, dormant or extinct.
Active Volcanoes
An active volcano is one that erupts continually or
periodically such as Mount Katmai in Alaska and Mount St.
Helens in the Cascade Range.
active
=
constant
Dormant Volcano
A volcano that has been known to erupt within modern times
but is now inactive is classified as a dormant volcano.
Mount Rainier in Washington state is an example of a
dormant volcano in the United States.
dormant
=
sleeping
Extinct Volcano
A volcano not known to have erupted within modern history is classified as an
extinct volcano. They have been worn away almost to the level of their magma
chamber. Mount St. Helens was considered to be dormant but erupted after
long periods of inactivity which proves that scientists can be wrong about a
volcano.
extinct
=
never
Where are the Volcanoes?
Count the total
amount of
active
volcanoes.
The Ring of Fire
Most volcanoes occur along
diverging plate boundaries,
such as the mid-ocean ridge,
or in subduction zones around
the edges of oceans.
video
Hawaii
A hot spot is an
area where magma
from deep within the
mantle melts through the
crust like a blow torch. Hot
spots often lie in the middle of continental or oceanic plates
far from any plate boundaries. Unlike the volcanoes in an island
arc, the volcanoes at a hot spot do not result from subduction.
video
References
Plate map and labeling diagram: World Book Encyclopedia Volcanoes Interfact
Animated Volcano: http://www.nsa.naples.navy.mil/disasterprep/art/volcano2.gif
Types of Volcano images: http://dknet.lineone.net/reference/encyclopaedia/hutchinson/images/c02745.jpg
Total active volcanoes: http://volcano.und.edu/vwdocs/frequent_questions/grp8/question63.html
NA total: http://www.pbs.org/wnet/savageearth/volcanoes/html/sidebar1.html
Ring of Fire total: http://volcano.und.nodak.edu/vwdocs/frequent_questions/grp8/question4361.html
Country totals: http://volcano.und.nodak.edu/vwdocs/kids/volcano_project/world.html
SA Total: http://www.hrw.com/science/si- science/earth/tectonics/volcano/volcano/region15/index.html
Ring of Fire Image: http://www.eia.doe.gov/kids/energyfacts/sources/renewable/images/RINGOFFIRE1.gif
Hawaii image: biology.usgs.gov/.../ PacificIslandPIERC.htm
Attachments
The_Dangers_and_Benefits_of_Volcanoes video 9.16.asx
Volcanoes_and_Lava video 2.10.asx
Yellowstone_Crater__Supervolcano.asf
Subduction__Magma_Chambers__and_the_Eruption_of_Volcanoes.asf
Volcanic_Mountains 5.46.asx
Magma_Inside_the_Earth 4.45.asx
Deadly_Eruptions video 6.49.asx
Mount_Vesuvius_and_Pompeii video 5.12.asx
Volcanoes 5.31.asx
Lava_Junkies 5.42.asx
The_Fire_Goddess 12.46.asx