Endogenic Process
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Transcript of Endogenic Process
VOLCANISMIts Features
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Albert Garcia’s award-winning photo taken on June 15, 1991 was chosen by Time as one of the “Greatest Images of the 20th Century” and also by the National Geographic Magazine as one of “100 Best Pictures” of the 20th Century. Garcia is currently the photo editor of Manila Bulletin.
Catastrophic
http://www.balita.com/mt-pinatubo20-photo-
exhibit-more-than-just-pictures-it-was-a-
reunion-of-survivors-2/
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VOLCANISM: Its Features
VOLCANISM?
Volcanism is the eruption of molten rock (magma) onto the surface of a planet. A volcano is the vent through which magma and gases are discharged. Magma that reaches the surface is called lava. Volcanos are named for Vulcan the Roman god of fire!
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VOLCANISM: Its Features
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How do volcanoes form?
What causes volcanoes to erupt?
Where do most volcanoes occur?
What are the different types of volcanoes?
What determines the degree of violence associated
with volcanic activity?
VOLCANISM: Its Features
Definition of termsA volcano is a vent or opening on planet’s surface which allows molten rock called magma, volcanic ash and gas to escape out onto its surface. A volcano gives a look like a mountain from which lava erupts. The hot magma erupting from a volcano is called lava.
ERUPTIONDefinition of Terms
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VOLCANISM: Its Features
Most volcanoes are formed by the movement of tectonic plates on the surface of the earth. These plates are basically huge pieces of rock that ‘float’ on the mantle (a layer of the earth that is sort-of liquid rock).
ERUPTIONHow Volcanoes Form
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TECTONIC
PLATES
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VOLCANISM: Its Features
ERUPTIONOrigin of Volcanoes
1. Magma rises2. As the magma rises it melts gaps in the surrounding rock3. As more magma rises a large reservoir 4. Pressure from the surrounding rock causes the magma to blast
5. The magma, now called lava, builds up at the vent forming a volcano.6. Often the volcano sides will be higher than the vent forming a depression called a crater
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VOLCANISM: Its Features
ERUPTIONWhat Causes Volcanoes to Erupt?
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TECTONIC PLATES
AND SETTINGS
Subducting Plate Margins
Spreading Plate Margins
Intraplate
(Hotspot)
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VOLCANISM: Its Features
Again, it’s in the edge of TECTONIC PLATES.
ERUPTIONAreas Where Most Volcanoes Occur
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VOLCANISM: Its Features
The Pacific Ring of Fire
ERUPTIONAreas Where Most Volcanoes Occur
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-It is a string of volcanoes and
sites of seismic activity around
the edges of the Pacific Ocean.
-It isn’t quite a circular ring. It
is shaped more like a 40,000-
kilometer (25,000-
mile) horseshoe.
-A string of 452 volcanoes.
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VOLCANISM: Its Features
ERUPTIONWhat determines the degree of violence associated
with volcanic activity?
Magma – molten rock or liquid that is mostly silica
Lava – solidified magma
Pyroclasts – from the Greek pyro, “fire”, and clast “broken”
– rock fragments (pyroclastic debris is also called tephra)
Lava flows – fissures in the ground
Extrusive rock - surface rock resulting from volcanic activity (rock formed by solidification of lava)
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VOLCANISM: Its Features
ERUPTION!What determines the degree of violence associated
with volcanic activity?
Crater – funnel shaped pit at the top of a volcano. formed when
material is blown out of the volcano by explosions
Caldera – when the volcano
collapses due to an empty
magma chamber
CRATER
CALDERA
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VOLCANISM: Its Features
ERUPTION!What determines the degree of violence associated
with volcanic activity?
DEVELOPMENT
OF A CRATER
LAKE
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VOLCANISM: Its Features
ERUPTION!What determines the degree of violence associated
with volcanic activity?
Whether eruptions are very explosive or relatively "quiet" is largely determined by two factors:
(1) the amount of gas in the lava or magma
(2) the ease or difficulty with which the gas can escape to the atmosphere
Viscosity – resistance to flow
PHYSICAL
CHARACTERISTICS
OF LAVA
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VOLCANISM: Its Features
ERUPTION!What determines the degree of violence associated
with volcanic activity?
FelsicContains more than
65% Silica
TYPES OF LAVA
MaficSilica (Poor) (45-52%)
RholiteBasaltAndesiteIntermediate
Silica
Composition
(53-65%)
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VOLCANISM: Its Features
The two most important factors that influence viscosity are the
(1) temperature of the lava relative to the cooler temperature which it solidifies
(2) the silica (Si𝑂2content of the lava)
ERUPTION!What determines the degree of violence associated
with volcanic activity?
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VOLCANISM: Its Features
ERUPTION!
Composite volcanoes
often form the largest
and tallest volcanoes.
They are the most
explosive and dangerous
of the types of volcanoes.
Types of Volcano
Composite
Volcanoes
Mt. Saint Helens in Washington state.
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ERUPTION!
Usually smaller in size
than composite
volcanoes, and the
eruptions are smaller
also. They form into steep
cone shaped hills.
Types of Volcano
Cinder Cone
Volcanoes
Paricutin in Mexico
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ERUPTION!
Shield volcanoes do not
erupt or explode like
composite or cinder cone
volcanoes. Shield
volcanoes have much
smaller eruptions
producing less ash.
Types of Volcano
Shield
Volcanoes
Muana Loa in Hawaii.
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ERUPTION!Pyroclastic flow descending Mayon volcano, Philippines.
-Most of the gas released during
eruption is water vapor
-Carbon dioxide, sulfur dioxide,
hydrogen sulfide, and hydrochloric acid,
are given off in lesser amounts
-Surface water introduced into a
volcanic system can greatly increase the
explositivity of an eruption.
-At high altitudes, the pyroclastics often spread out into a dark, mushroom cloud. The fine
particles are transported downwind by high atmosphere winds. Eventually debris settles
back to earth under gravity's influence as ashfall (or sometimes pumicefili) deposits.
A pyroclastic flow is a mixture of gas and pyroclastic debris that is so dense that it hugs the
ground as it flows rapidly into low areas.
Gases and Pyroclastics
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VOLCANISM: Its Features
ERUPTION!Types of Volcanic Eruptions
In a Hawaiian eruption, fluid lava is ejected from a
vent as fire fountains or lava flows. The 1969 eruption
at Mauna Ulu, a vent of Kilauea Volcano in Hawaii,
was a spectacular example of fire fountaining. Photo
by D.A. Swanson, USGS, August 22, 1969.
Hawaiian Eruption
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VOLCANISM: Its Features
ERUPTION!Types of Volcanic Eruptions
Short bursts of glowing lava,
created from the bursting of
large gas bubbles at the
summit vent of a volcano typify
a Strombolian eruption. This
photo, taken from the summit
of Stromboli, a volcano in the
Aeolian Islands, Italy, shows a
classic example of this activity.
Photo by Andrew Hague,
Istockphoto.com.
Strombolian Eruption
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VOLCANISM: Its Features
ERUPTION!Types of Volcanic Eruptions
Relatively small but violent
explosions of viscous lava create
columns of ash and gas and
occasional pyroclastic flows, as
seen at this eruption of the
Santiaguito volcanic dome
complex in Guatemala. Photo by
Jessica Ball, March 15, 2009.
Vulcanian
Eruption
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VOLCANISM: Its Features
ERUPTION!Types of Volcanic Eruptions
The largest and most violent of all explosive
eruptions, Plinian eruptions send columns of
pulverized rock, ash, and gases that rise miles
into the atmosphere in a matter of minutes.
Mount St. Helens in Washington State
experienced a Plinian eruption following a major
flank collapse in 1980. Photo by Austin Post,
USGS, May 18, 1980.
Plinian Eruption
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VOLCANISM: Its Features
ERUPTION!Types of Volcanic Eruptions
Lava domes, such as this example in
the crater of Mount St. Helens, are
piles of viscous lava that are too cool
and sticky to flow far. Domes grow and
collapse in cycles, and often form at
volcanoes that also experience Plinian
eruptions. Photo by Lyn Topinka,
USGS, August 12, 1985.
Lava Dome
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VOLCANISM: Its Features
ERUPTION!Types of Volcanic Eruptions
Lava erupting through water
creates the dramatic plumes
of scoria and billowing ash-
and-gas clouds of a
Surtseyan eruption. The type
example of this eruption
occurred at Surtsey, a
volcanic island off the coast
of Iceland. NOAA image of
the 1963 eruption.
Surtseyan Eruption
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VOLCANISM: Its Features
ERUPTION!Types of Lava Flow
A smooth and continuous
lava crust. Pahoehoe forms
when the effusion rate is
low and consequently the
velocity of lava flow is slow.
Pahoehoe lava flow is
usually at least 10 times
slower than typical aa lava
flow.
Pahoehoe
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VOLCANISM: Its Features
ERUPTION!Types of Lava Flow
Aa lava is a rough rubbly
crust of a lava flow. It is a
major lava flow type.
Aa
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VOLCANISM: Its Features
ERUPTION!Types of Lava Flow
A distinctive lava flow morphology
that has been appearing in our
dredges is pillow lava. Pillow lavas
form when hot lava flows into water
and cools rapidly, creating long
tubes and bulbous pillow-shaped
mounds of rock. Pillow lavas are
found not only in the ocean but
also under glaciers that overlie
volcanoes.
Pillow Lava29
VOLCANISM: Its Features
ERUPTION!Types of Lava Flow
Blocky flows are
common if the silica
content of lavas is
higher (composition
of basaltic andesite to
rhyolite).
Blocky
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VOLCANISM: Its Features
ERUPTION!Three Definitions of Volcanoes
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VOLCANISM: Its Features