VOLCANOES

SHEEBA. J

Presentation By

~An opening in the earth's crust through

which molten lava, ash, and gases are

ejected.

~A similar opening on the surface of another

planet.

~A mountain formed by the materials ejected

from a volcano.

What is A Volcano?

The types Of Volcanoes

~ Shield Volcano

~ Cinder Cone Volcano

~ Composite Volcano

~ Caldera Volcano

~ Fissure Volcano

Shield volcanoes can span across hundreds of miles

and they can be huge vertically that they can reach

the clouds of earth very easy. Shield volcanoes have

a slow slope and consist of frozen lava after it is

hardened. Shield volcanoes almost always have

large craters at their summit.

Cinder cone volcanoes consist of mostly loose,

grainy cinders and have very little to no lava.

Cinder cone volcanoes are normally small about a

miles span and about one thousand feet vertically.

Cinder cone volcanoes have fairly steep slopes and

normally have a small crater at the top.

Composite volcanoes have another name called

“Strato Volcanoes.” Composite volcanoes consist of

lava that is mixed with sand or gravel which in turn

creates cinders or volcanic ash.

Caldera volcanoes are circular depressions in the

ground over a magma chamber. Sometimes the

depression in Caldera volcanoes are covered in

with lava and volcanic ash making it hard to

recognize. This type of volcano is easier noticed

from space due to the distance and view point.

When this volcano erupts it can spew volcanic

rocks for miles and miles.

http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

Fissure volcanoes are also hard to recognize from

the ground and sometimes from space. Fissure

volcanoes have no main crater, the ground just

splits and lava pours out through the cracks. After

a fissure volcano erupts and has cooled because it’s

a solid it will look mainly like the plains.

http://www.cotf.edu/ete/modules/volcanoes/vtypesvolcan1.html

Types Of MagmaGranite magma consist of light-colored rock and is

not as heavy as basalt magma. Granite magma is

very sticky and flows rather slowly.

Basalt magma consist of dark-colored rocks and is

much heavier then granite magma. It flows more

fluidly then molten granite.

Volcano Environments

~In an island-arc environment, volcanoes lie

along the crest of an arcuate.

~In an oceanic environment, volcanoes are

aligned along the crest of a broad ridge that

marks an active fracture system in the

oceanic crust.

~In the continental environment, volcanoes

are located unstable, mountainous belts that

have thick roots of granite or granite like

rock.

Where are volcanoes likely to

occur?

Volcanoes occur in weak spots in the earth’s crust

There are many volcanoes along the Pacific Ocean.

Many islands in the Pacific Ocean are actually

volcanoes. They form a ring around the ocean

which is called the “Pacific Belt of Fire.”

Although there are some other “belts of fire”, the

“Pacific Belt of Fire” is the biggest.

There are approximately five hundred active

volcanoes, that are known, lying in these belts.

When and how do eruptions occur?

Steam and gases from magma in the earth create

bubbles that expand and burst when the pressure

above them is lessened. These bubbles usually burst

with a tremendous force that along with escaping

gas comes magma too. In some cases, it takes years

for the magma to break through the surface of the

earth.The first recorded eruption was in 781 (Fuji,

Honshu, Japan)The most recent recorded eruption was

in 2002 (Etna, Sicily, Italy)

Why do eruptions occur?

Eruptions occur when underground pressure is

released when blocks of the earth’s crust shift.

For example, earthquakes.

Damages

The most devastating destruction from volcanoes

is the tremendous loss of life. Following an

eruption in 1815, there were 56 000 people killed by

a tidal wave from a eruption. Lava from the

volcano is hot enough to catch everything in its path

on fire, even the ash from a volcano is hot enough

to start fires. Lahar can wash away houses and

uproot trees. Magma can give off poisonous gases

such as carbon monoxide. Damages from

volcanoes are very expensive to repair or replace.

Thank You