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Volcanoes
What do we know
about them?
The earth is made up of 3
different Layers
The inner Core
The core of the earth is in 2 parts,
the solid inner core and the molten
liquid outer core.
The inner core of the earth is mostly
made of iron and nickle.
The Outer core is super heated lava found 3000
miles below the earths surface.
The outer core
The mantel
the mantel is super heated rock which
represents 85% of the weight of the
earth!
This is about 1,800 miles thick.
The crust
The crust is what separates us from the mantel.
Is is around 18 miles thick, this is the part
that we live on.
The Earth's rocky outer crust solidified billions of years ago, soon after the
Earth formed. This crust is not a solid shell; it is broken up into huge, thick
plates that drift atop the soft, underlying mantle.
Tectonic Plates
The plates are made of rock and drift all over the
globe; they move both
horizontally (sideways) and vertically (up and down). Over long periods of time,
the plates also change in size as their margins are added to, crushed together, or
pushed back into the Earth's mantle. These plates are from 50 to 250 miles (80 to
400 km) thick.
The area encircling the Pacific Ocean is called the
"Ring of Fire," because its edges mark a circle of
high volcanic and seismic activity (earthquakes).
Most of the active volcanoes on Earth are located on
this circumference. On the edge of the Pacific
Ocean, the edge of the Pacific Continental Plate is
expanding in the seabed, and is hitting the North
American Plate, the Nazca Plate, the Eurasian Plate,
and other plates, causing the margins of the plates
to collide, buckle, and compress, causing
earthquakes and volcanoes.
What do the plates have to do with volcanoes?
Most volcanoes are formed by the movement of tectonic plates on the surface of the earth.
The tectonic plates are in constant motion, albeit very slow motion. They sometimes move toward each
other, other times they’ll move apart, and still other times one will sink while the other rises above it.
When a tectonic plate sinks, it sinks down into the mantle and becomes very hot.
So hot, in fact, that the rock melts. This molten rock will gradually make its way
up to the surface of the earth through a series of cracks. When it reaches the
surface of the earth, we refer to it as lava. As layer upon layer of lava builds up, a
volcano is formed.
What do we call lava when it is
under the surface?
A: Magma!
Answer
There are many factors that determine what kind of lava flow will occur and what type
of volcano it will be. The amount of gas trapped in the lava, the kinds of minerals
making up the lava, and how much pressure can be trapped in the area all affect the
eruption and formation of the volcano.
Definitions
Crater - Mouth of a volcano - surrounds a volcanic vent.
Conduit - An underground passage magma travels through.
Summit - Highest point; apex
Throat - Entrance of a volcano. The part of the conduit that ejects lava and volcanic ash.
Ash - Fragments of lava or rock smaller than 2 mm in size that are blasted into the air by
volcanic explosions.
Ash Cloud - A cloud of ash formed by volcanic explosions.
Magma - Molten rock beneath Earth's surface.
Parasitic Cone - A small cone-shaped volcano formed by an accumulation of volcanic
debris.
Sill - A flat piece of rock formed when magma hardens in a crack in a volcano.
Vent - An opening in Earth's surface through which volcanic materials escape.
Flank - The side of a volcano.
Lava - Molten rock that erupts from a volcano that solidifies as it cools.
Did you know?
The name "volcano" has its origin from the name of Vulcan, a god of
fire in Roman mythology.
Where is the ring of fire?
There are several types of volcanoes and
these come in 3 different forms.
Active volcanoes are volcanoes that have erupted
in recent history or are continually erupting.
Here are some examples of active volcanoes.
Kilauea Volcano on the island of Hawaii (the Big Island) is
widely considered to be the most active volcano on Earth.
Over the course of its most recent eruption which began in
January of 1983, the volcano has expelled enough lava to
pave a road around the planet three times over.
Mount Etna, on the Italian island of Sicily, has been erupting more
or less continuously for the past 2,000 years though its overall
history stretches back approximately 300,000 years. Though
somewhat less famous (or infamous) than neighboring Mount
Vesuvius, Mount Etna greatly outclasses the latter peak as it
rises 2.5 times its height. In addition, most of Etna’s more
spectacular eruptions and associated geological events occurred
in prehistory. The volcano erupted in every year from 200
through 2008 and its recent eruption occurred in April of 2010.
The Sakurajima volcano is located on what was formerly an
island in southern Japan’s Kagoshima Bay. The island is
now connected to the mainland via a low-lying peninsula
created by lava flows during the mountain’s immense
eruption of 1914. Sakurajima stands 3,665 feet (1,117m)
above sea level and has been erupting more or less
continuously since 1955.
The Chaitén volcano in southern Chile began erupting on May 2 of
2008, an event that caught scientists by surprise as the mountain’s
last eruption was estimated to have occurred about 9,500 years
ago. Though the mountain is still in an eruptive state, the initial
stages were marked by the expulsion of voluminous ash clouds
shot through by incandescent bolts of lightning.
Extinct Volcanoes
Extinct volcanoes are those that scientists consider unlikely to erupt again, because the volcano no longer has a lava
supply.
Edinburgh Castle is built on an
extinct volcano.
Dormant Volcanoes
It is difficult to distinguish an extinct volcano from a dormant one. Volcanoes are often considered to
be extinct if there are no written records of its activity. Nevertheless, volcanoes may remain dormant
for a long period of time.
Vesuvius was described by Roman writers as having been covered with gardens and vineyards before
its famous eruption of AD 79, which destroyed the towns of Herculaneum and Pompeii. Before its
catastrophic eruption of 1991, Pinatubo was an inconspicuous volcano, unknown to most people in
the surrounding areas.
Pinatubo, 1991
Vesuvius, AD 79
Video Footage
Use the following link to access National Geographic Site and view the video footage on volcanoes.
Look out for the under water eruption footage.
http://video.nationalgeographic.com/video/player/environment/environment-naturaldisasters/volcanoes/volcano-lava.html