Transcript VOLCANO’S ACTIVITY

VOLCANIC ACTIVITY
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WHAT IS A VOLCANO ?
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A volcano is a rupture on the crust of a planetary-mass object, such as Earth, that
allows hot lava, volcanic ash, and gases to escape from a magma chamber below
the surface.
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WHY DOES A VOLCANO FORM?
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You have already learned about tectonic plates. Beneath the Earth surface, powerful
forces are at work. These forces move lithospheric plates and produce huge
chambers of magma, molten rock beneath the Earth crust.
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HOW DOES A VOLCANO FORM:
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When tectonic plates collide, one plate can be pushed beneath another. As it sinks it
heats up and begins to melt. This molten rock then rises and erupts on the surface as
lava, building up a volcano.
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HOW DOES A VOLCANO FORM 2:
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Figure 8.2: A volcano is a vent through which molten rock and gas from beneath the Earth
surface escape.
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(1) Large magma chamber (2) Bedrock
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(3) Pipe (conduit) (4) Layers of ash
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(5) Layers of lava (6) Lava flow (7) Vent
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(8) Lava (9) Ash cloud (26)
As you can see in this picture, magma begins in the lava chamber and comes to the surface through
the throat of the volcano. The volcano is constructed layer by layer, as ash and lava solidify, one
upon the other.
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WHERE DOES A VOLCANO OCCUR?
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Magma is a molten rock that has been heated because of high temperatures and
pressures beneath the Earth crust. This pressure mostly occurs where the tectonic
plates meet and subduct.
So, volcanic activity tends to
occur along the subduction
plate boundaries, where one
plate slides
underneath another one.
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THE RING OF FIRE:
The edges of the
Pacific Plate make
up a long subduction
boundary.
The Pacific Ring of Fire is where the majority of the
volcanic activity on the Earth occurs.
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VOLCANIC HOT SPOT:
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Although most volcanic activity on Earth occurs at plate boundaries, there are some
volcanically active spots that are in the middle of a tectonic plate. These areas are called
hot spots.
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The islands of Hawaii formed over a hot spot and are not located on the Pacific Ring of
Fire. It was formed by volcanic activity fed by mantle plumes.
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VOLCANIC ERUPTION:
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All volcanoes share the same basic features.
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The magma collects in magma chambers that can be 160 kilometers (100 miles)
beneath the surface.
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As the rock heats, it expands, which creates even more pressure.
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As a result, the magma seeks a way out pushing toward the surface, the magma
seeps through cracks in the Earth crust called vents.
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Eventually, the magma reaches the surface; when it comes out, we call it an
eruption.
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TYPES OF ERUPTIONS:
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Their composition and construction depend on so many factors, that it would be
impossible for two formations to be exactly alike.
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In the same way, each volcano and its eruptions are unique.
• However, we tend to see two major kinds of eruptions:
• Explosive Eruption
• Effusive Eruption
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EXPLOSIVE ERUPTION:
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An explosive eruption is a
volcanic term to describe a
violent, explosive type of eruption.
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Such eruptions result when
sufficient gas has dissolved under
pressure within a viscous magma
such that expelled lava violently
froths into volcanic ashes when
pressure is suddenly lowered at
the vent.
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(in the picture Mount Saint Helens
explosive eruption on July 22nd,
1980)
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EFFUSIVE ERUPTION:
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An effusive eruption is a volcanic eruption characterized by the outpouring of lava onto the
ground .
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Lava flows generated by effusive eruptions vary in shape, thickness, length, and width
depending on the type of lava erupted, discharge, slope of the ground over which the lava
travels, and duration of the eruption.
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For example, basalt lava may become ʻaʻā or pāhoehoe.[2] Andesite lava typically forms blocky
lava flows,[3] and dacite lava flows often form steep-sided mounds called lava domes due to
their viscosity.[4]
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An ʻā lava flow from Mauna Loa during its 1984 eruption.
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LINK
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https://www.youtube.com/watch?v=WgktM2luLok
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https://www.youtube.com/watch?v=BcFtpWjZwlE
SUMMARY
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https://www.youtube.com/watch?v=N9ncfAsmiSg
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https://www.youtube.com/watch?v=N9ncfAsmiSg
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https://www.youtube.com/watch?v=eV0Rl0gKiSI
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