Volcanoes are openings in the Earth where lava reaches Earth's surface.
Volcanoes, named after the Italian island Vulcano, consist of a vent, pipe,
crater, and a cone. The vent is an opening on the Earth's surface
were the lava is released. The pipe is where the magma comes from
during an eruption. The crater is the bowl shaped depression at the
top of a volcano. And the cone is the outside or the cover of a volcano.
Volcanoes are classified by their shape and what it's made of. There
are five types of volcanoes each one unique in a certain way. The
five types of volcanoes are composite, shield, cinder cone, spatter cone,
and complex or compound volcanoes.
Composite volcanoes are made of lava and rock, and often exceed 2,500 meters
in height. Between eruptions of this volcano, it appears to become
extinct, but when it erupts is very explosive making it one of the most
dangerous kind of volcanoes. Shield volcanoes are made by running
lava flows. Cinder cone volcanoes are made of lava fragments and
cinder. These volcanoes are usually steep and reach an average height
of 250 meters. Spatter cone volcanoes are the type that don't really
explode, but they don't really have just running lava. And Complex
volcanoes are volcanoes that erupts with two or more vents.
Mount St. Helens
Mount St. Helens is a volcano in the northwestern part of America, in a
state known as Washington. The volcano is about 8,300 ft in height
and last erupted on May 18, 1980. Mount St. Helens is a classified
as a stratovolcano.
When the volcano erupted, 1,300ft disappeared from the top of it.
The ash covered approximately 150 sq. miles. The ash also shot up
to about 25,000-50,000ft above sea level. The eruption was so strong that
vegetation was damaged 13 miles away from the volcano. The temperature
was said to have reach 570-1,350 degrees Fahrenheit.
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St. Helens
Oahu,
Hawaii
Oahu, Hawaii is an island made up of two different volcanoes. The
volcanoes are named Waianae and Koolau. Both of these volcanoes were
formed from a hot spot under the sea.
Waianae is the oldest out of the two and makes up the western part of the
island. Koolau is a large basaltic volcano that makes up the eastern
part of Oahu. Both of these volcanoes are shields and are both heavily
eroded due to landslides. Waianae is about 3.8 million years old
and Koolau is about 2.7 years old.
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Hawaii
Hazards
There are many things that you have to look out for when being around a
volcano. When a volcano erupts you should be very far away from it,
but if you aren't there are other things that can harm you other than the
explosion itself. Pycroclastic is a mixture of hot gas, ash , and
rock. Nuees Ardennes is a mixture of gas, lava, blocks, ash, and
pumice. Nuees Ardennes acts like an avalanche and can reach a speed
of 500kph. A blast happens when there's a sudden reduction of pressure,
causing gases and magma to blast out of the volcano. Some other things
that you have to look out for are volcanic ash, lagars, debris, avalanches,
landslides, tsunamis, lava, and gases.
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Causes
of Eruptions
An eruption begins when the pressure on a magma chamber forces the
magma to go through the conduit and out the vents. When the magma
chamber is filled up it erupts. The eruption depends on the kind
of gases, silica, and magma. The silica is what makes the magma sticky
and water during an eruption gives the volcano steam.
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of Eruptions
Signs
that an Eruption is Likely
There are many things that usually happen before there is an eruption.
Although you can tell when an eruption is likely you won't be able to tell
what kind of an eruption is coming. Frequent earthquakes. swelling
of ground surfaces, hot ground, temperature changes, and detection of volcanic
gases are some of the signs of a likely volcano eruption.
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that an Eruption is Likely
Volcanoes
