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The Ring of Fire
Retrieved from: http://www.universetoday.com/59341/pacific-ring-of-fire/#ixzz2klYkvCjr
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What is the Ring of Fire?
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sample questions and or comments:
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The Pacific Ocean Ring of Fire is an area of major seismic and
volcanic activity. The Ring of Fire lies in a band (horseshoeshaped) of oceanic trenches and volcanic arcs circling the Pacific
basin ocean which extends for approximately 40,000 km (25,000
miles) long. The Pacific Ring of Fire contains more than 450
volcanoes which stretches from the southern tip of South
America, up along the coast of North America, across the Bering
Strait, down through Japan, and into New Zealand. Nearly 90%
of the world’s earthquakes occur along the Ring of Fire. Of the
world’s active volcanoes, almost 90% are in the Ring of Fire.
The following is an outline of interesting facts about the Pacific
Ocean’s “Ring of Fire.”
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Volcanic Arcs and Trenches
Volcanic arcs are volcanic mountain ranges that form in
subduction zones when a continental plate and an oceanic plate
converge. The heavier oceanic plate bends and moves slowly into
the mantle. The water soaked oceanic crust begins to melt as it
descends beneath the ocean floor. Trenches are depressions
located in the Earth's crust. A cross sectional view of trenches is
generally V-shape.
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Active Volcanoes
The Ring of Fire is the home of most of the active volcanoes on
Earth, most of them located on the rings eastern edge. Mount
Ruapehu in New Zealand is one of the more active volcanoes in
the Ring of Fire, with yearly minor eruptions and major eruptions
occurring about every 50 years.
Krakatoa, an island in Indonesia, erupts less often than Mount
Ruapehu, but much more spectacularly. Beneath Krakatoa, the
Australian Plate is being subducted beneath the Eurasian Plate.
An eruption in 1883 destroyed the entire island, sending volcanic
gas, ash, and rocks as high as 80 kilometers (50 miles) in the air.
A new island volcano, Anak Krakatau, has been forming with
minor eruptions ever since.
The Ring of Fire is a direct effect of plate tectonics and the
collisions of lithospheric plates. The Ring of Fire is well-known
for its frequent earthquakes and volcanic activity which
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correspond with the boundaries of one of the world´s major
tectonic plates.
Theory of Plate Tectonics
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The theory of the tectonic plates which derives from the concepts
of continental drift were developed during the first decades of the
20th century; however, the concept was not accepted by
geoscientists until the concepts of sea floor spreading were
developed in the late 1950s and early 1960s. On earth, there are 8
major plates and many minor plates. Oceanic trench formation,
mountains, volcanoes, and mid-ocean ridges occur along the
boundaries of these plates. The lateral movement of the plates
varies from 0-100 mm per year.
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Tectonic plates are continuously colliding, sliding, and forcing
themselves underneath other plates. In the Pacific Ocean, in the
area around the ring of fire, the ocean floor is divided into
several plates. Of these, the largest one is the Pacific Plate, which
is sliding underneath the plate that maintains North America.
This process of sliding underneath other plate is called
subduction, and the seismic and volcanic active region along the
sliding plates is known as the subduction zone. The tremendous
amount of energy generated by these plates melts rock into
magma, creating “The Ring of Fire.”
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Plate Boundaries
The Ring of Fire is the result of plate tectonics. The edges of
several tectonic plates meet along the Ring of Fire, resulting in a
convergent boundary, a divergent boundary, or a transform
boundary.
A convergent plate boundary is formed by tectonic plates
crashing into each other. Convergent boundaries are often
subduction zones, where the heavier plate slips under the lighter
plate. Subduction zones are frequently sites of volcanoes, as the
heavier plate melts back into the Earth’s mantle.
Mount St. Helens, in the U.S. state of Washington, is an active
volcano in the Ring of Fire. Below Mount St. Helens is a
convergent boundary between the Juan de Fuca Plate and the
North American Plate. The small Juan de Fuca Plate is associated
with the massive, heavy Pacific Plate. Both the Juan de Fuca and
Pacific plates are being subducted beneath the North American
Plate.
A divergent boundary is formed by tectonic plates pulling apart
from each other. Divergent boundaries are the site of seafloor
spreading. Seafloor spreading is the process of magma welling
up in the rift as the old crust pulls itself in opposite directions.
Cold seawater cools the magma, creating new crust.
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The East Pacific Rise is a site of major seafloor spreading in the
Ring of Fire. The East Pacific Rise is located on the divergent
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boundary between the Pacific Plate and the Cocos Plate (west of
Central America), the Nazca Plate (west of South America), and
the Antarctic Plate.
A transform boundary is formed by two tectonic plates sliding
next to each other. Transform boundaries are often the site of
earthquakes in the Ring of Fire.
The coast of the U.S. state of California is prone to earthquakes.
It lies on the transform boundary between the North American
Plate, which is moving south, and the Pacific Plate, which is
moving north.
Significance of The Ring of Fire
The Ring of Fire is a crucial region for many reasons. It serves as
one of the main boundary regions for the tectonic plates of over
half of the globe. It also affects the life of millions if not billions
of people who live in these regions. For many of the people who
live in the Pacific Ring of Fire, the reality of a volcanic eruption
or earthquake is commonplace and a challenge they have come to
deal with over time. At the same time the volcanic activity has
also provided many valuable resources such as rich farmland.
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Questions to be answered in your Science Notebook (please do not forget to write paragraph and sentence numbers):
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Where is the Ring of Fire located?
How many major plates exist?
What causes the Ring of Fire to be so active?
What is generated from the plate boundaries continuous movement?
Describe the types of plate boundaries that are at the Ring of Fire and give examples.