Transcript Parts of a Volcano

Parts of a Volcano






1. Gas emission: various gases such as CO2,
H2O, nitrogen, and lesser gases such as chlorine,
hydrogen, and argon.
2. Crater: depression connected to magma
chamber via a pipe aka caldera
3. Lava: magma that has reached the surface
4. Rock
5. Vent or pipe: conduit that connects magma
chamber to the crater
6. Magma chamber: area where magma accumulates within the
volcano

7. Fumorale: vent that emits only gases
Anatomy Of A Volcanic Eruption!
1.
2.
3.
4.
5.
Intense heat from magma cracks the rocks near the
surface. The cracking rock produces an earthquake!!
Hot blasts of high pressure gases expand the cracks and
develop a passage to the surface.
Hot gases with rock fragments create a larger conduit or
pipe. Volcanic pipes are created due to increase in
pressure. A bulge is created due to gas build up.
Pipes enlarge, magma moves upward to produce an
eruption.
Pipes can become clogged with cooled magma and debris.
Gas pressure can build up an cause another eruption.
What determines how violent an
eruption will be?

The viscosity of the magma determines
how violent an eruption will be.
What is viscosity?



The resistance of material to flow.
A very viscous material is very thick and
flows slowly.
When thinking of a volcano…the more
viscous the magma is, the more explosive
the eruption will be!
What influences the viscosity of
magma?



Temperature
Chemical composition of the magma
Amount of dissolved gases (H2O and CO2)
Temperature


Fluidity (flow) and mobility (movement) is
strongly influenced by temperature.
Cool lava congeals (becomes solid) just
like making jello. The mobility and flow
stops.
Magma Chemical Composition



Viscosity is directly related to silica content.
The more silica the greater the viscosity.
Flow is slowed due to the long chains of silica
molecules


Felsic(high in silica) very viscous, short, thick flows.
Mafic (low in silica) quite fluid, travels long
distances
Dissolved Gases



Dissolved gases increase the fluidity of
magma.
Escaping gases expand as pressure
decreases.
This provides the force to propel molten
rock.
Non-explosive Eruptions




Fluid lava (basalt) magma allows for
expanding gases to be released with ease.
Release huge amount of lava
Most common type of volcanic eruption
The northwest U.S. region, the Hawaiian
Islands and the mid-ocean-ridge are all
examples of non-explosive eruptions.
Explosive Eruptions



Highly viscous magmas explosively expel
jets of hot ash, gases, and other debris.
Instead of producing lava flows, explosive
eruptions cause molten rock to be blown
into tiny particles (thousands of fragments
of glass)
Examples of explosive eruptions: Mt. St.
Helen’s, Mt Pinatubo in the Philippines
Effects of Volcanic Eruptions


Volcanic ash and gases spread throughout
the atmosphere.
They can block out enough sunlight to
cause global temperatures to drop.
Effects of the Mount Tambora
eruption (1815) on humanity:







Ash blanketed the skies of Indonesia and caused 3 days of
total darkness.
Estimated that 12,000 people died directly from the blast.
80,000 people died from the resulting hunger and disease.
caused global temperature to drop
affected the global climate a year later
affected temperatures enough to cause food shortages in
N.America and Europe
The summer was called the Summer of Starvation.
Volcano Types




Plumes
Shield
Cinder cone
Composite or Stratovolcano
Plumes





stationary hot spots erupt as volcanoes
Magma comes from deep within the mantle.
As crust moves, the volcano will move off hot
spot and become extinct.
A new volcano will form.
example: Hawaiian Island Chain
Hot Spots





Volcanically active places on Earth’s surface that
are far from plate boundaries OR
Another theory is that hot spots are magma
plumes along cracks in the plates.
Hot spots always form long chains of islands.
What theory is true???
Yellowstone is a hot spot. It is unusual to have a
hot spot under a continent.
Shield Volcano




Built of layers of lava released from
repeated non-explosive eruptions
Lava is runny and spreads out over a wide
area.
Layers of lava create a volcano with gently
sloping sides
Although they are not steep, they are
enormous in size.
Shield Volcano
Cinder Cone Volcano





Made of pyroclastic material usually produced
from moderately explosive eruptions
Usually small and erupt for only a short period of
time.
Forms steep slopes.
Usually occurs in clusters, commonly on the sides
of other volcanoes
Erode quickly due to loose pyroclastic material
Cinder Cones
Composite Volcano aka
Stratovolcano





Most common, nearly symmetrical structure
Composed of alternating lava follows ad
pyroclastic material
Produced from relatively viscous lavas, may
extrude lava for a long period, or suddenly erupt
violently.
Broad bases and steep sides
Examples: Western region of the U.S. includes
Mt. Hood, Mt. Rainier, Mt Shasta, and Mt St.
Helen.
Composite Volcano
Sea Vents
A
sea vent is a fracture or crack in the ocean
floor where pressure is constantly being
released.
Interesting life forms live there.
No sunlight, only chemicals to survive on
This is the only place on Earth where
organisms don’t rely on the sun.
Click on the link below and follow the
directions on your worksheet.
http://www.kids.discovery.com/games/pompe
ii/pompeii.html