Download Hill Barter, Kristina Scapin, Amy Schneider Volcanoes

Volcanoes
BY: Kristina
Scapin
Amy
Schneider
Hillary Barter
How are volcanoes formed?
• One way is in the
‘subduction zones’
(Earth’s crust), which is
made up of a series of
tectonic plates that move
over the molten mantle,
which is relative to each
other.
• One plate is forced under
another when the
collision occurs, and it
melts while being pushed
into the hot mantle.
• Magma is the molten rock
which makes its way up
to the top while pushing
through the crust.
• Some of the magma
cools and then is trapped
in the crust, but the rest
shoots upwards, thus
forming the volcano.
When a Volcano erupts…
• Lava flows- usually they
are slow enough so that
people can get out of the
way.
• Falling Ash- magma
breaks into pieces and
bursts from the volcano.
• Glowing Avalanches- very
hazardous.
• Mud and Debris flows
Hot Spots
• Hot Spots are places on Earth where the
crush is heated strongly by the mantle
below.
• As the crustal plates move over them, a
string of volcanoes begins to develop.
A Volcanic Eruption!
• In this photograph, a
volcano is erupting.
This occurred in Mt.
Etna, Sicily.
Pahoehoe
• Below is a picture of pahoehoe, which is
what the lava looks like once the volcano
is done erupting.
Lava…
• In this picture, lava is
flowing upwards to
the top of the volcano.
3 Main Types of Volcanoes:
• Scoria Cone
• Shield Volcano
• Stratovolcano
Scaoria
• Also called cinder cones.
• They are the most common volcano, smallest (height is
usually less then 300 meters)
• Composed of ejected basaltic tephra. The tephra
usually contains gas bubbles which gives it a cindery
appearance.
• Most cinder cones are symmetrical with straight sides
and a very large summit craters.
Shield Volcano
• These volcanoes are broadly shaped with a
width usually around 100 kilometers.
• Its height is usually 1/20th of its width.
• Their shape is caused by the extrusion of
basalt lava that spreads over the summit area.
• These volcanoes are generated from Hawaiian
eruptions. (They are usually calm eruptions
with a steady flow of lava coming out of them.)
Stratovolcano
• Is also called composite cones.
• These volcanoes are the ones that many people
recognize.
• They are also the most deadly of the volcano types.
• The bottom of the volcanoes are not as dangerous as
the tops of stratovolcanos.
• Due to lateral blast, some volcanoes contain several
eruptive centers, or a caldera.
• Typically, stratovolcanos form convergent plate
margins. (One plate lowers down beneath an adjacent
plate in the subduction zone.)
Active Volcanoes
• Active volcanoes are ones that have
erupted recently or one that volcanologists
believe might erupt soon. They are kept at
very close watch to ensure the safety of
the people and animals in the area.
Dormant Volcanoes
• Also known as sleeping volcanoes, these have been
quiet for quite some time but still show signs of erupting.
• A volcano becomes dormant when the vent is blocked by
hardened lava, called a plug, or if the magma seeps
back under the Earth’s crust.
• A volcano could be dormant for hundreds of years and
then suddenly erupt again, usually being very violent.
• The eruption is so violent because the pressure
underneath the plug builds up, so the plug gives away
and a large eruption occurs. Then the volcano is
classified as active again.
Extinct Volcanoes
• An extinct volcano is one that has not
erupted for thousands of years.
• Sometimes it is hard to tell if a volcano is
dormant or extinct, so they will be listed as
dormant until volcanologists are sure there
will be no more eruptions
• Example: Mount Vesuvius in Italy
Famous Volcanoes
• The first recorded Volcano was Mount Etna in Sicily, Italy
in 475 B.C. It has erupted 250 times since then. The
latest eruption was in 1979 when a new crater opened
without warning and erupted.
• Mount Vesuvius in Italy is an extinct volcano, known
mostly for it’s destruction. It erupted on August 24, 79
A.D. and 2,000 people died when they were buried
under ash and mud. There was no liquid lava, only
volcanic ash and volcanic bombs.
It has been dormant since 1944
but volcanologists think that it may
become active again.
Mt. Vesuvius Erupting
Famous Volcanoes (cont.)
• In 1902 Mount Pelee on an island off Martinique a
volcano erupted without disaster. It was an old volcano
with a crater filled with water.
• The Mexican volcano, Paricutin formed in a cornfield
without notice and erupted in 1852 and has been
dormant since.
• On May 18, 1980 Mount St. Helens on the coast of
Washington erupted for the first time in 120 years. The
eruption was as strong as 30,000
• atomic bombs. When it exploded,
• a huge area was ripped out from
• it’s sides and left a large crater.
• The eruption lasted 9 hours. Due
• to Volcanologists prediction, many
• people had left their homes,
Mt. St. Helen’s
• although sixty people were killed.
Famous Volcanoes (cont.)
• Mount Fuji is the highest and most sacred mountain in
Japan. It is a dormant volcano and last erupted in 1707.
• The largest volcano in the world is in Mauna Loa,
Hawaii. It is 30,000 feet above the ocean floor and is 60
miles wide at the base. It has erupted 40 times in the last
150 years.
• The tallest volcanoes are in Chile, South America.
• Volcanoes that are always erupting: Stomboli in Italy,
Yasur in the Pacific Ocean, and Erta’Ale in Africa.
• Furnace Peak in the Indian Ocean is the volcano that
has erupted the most times in the 20th century, it has
erupted 80 times since 1900.
Bibliography
• http://www.geology.sdsu.edu/how_volcanoes_w
ork/
• http://www.learner.org/exhibits/volcanoes/
• http://www.sciencenet.org.uk/database/earth/ear
thscience/g00178d.html
• http://www.minerals.co.nz/html/main_topics/reso
urces_for_schools/volcanoes/volcanoes_world_f
amous.html
• http://www.groton.k12.ct.us/WWW/fsr/student/Sp
ring02/Volcano/famous_volcanoes.htm
• http://www.famousvolcanoes.netfirms.com/