Download 5a what_is_a_volcano

cool fact!
• The term “volcano” is from the Latin Volcanus
or Vulcan, the Roman god of fire.
neat fact!
• The most formidable volcanoes are called
supervolcanoes. A supervolcanic eruption can
rain hellfire across thousands of miles and cause
worldwide climatic changes, such as a drop in
global temperature due to the release of tons of
ash particles into the atmosphere. These
monsters rear there ugly heads only ever few
hundred thousand years, however. One of the
biggest is in Yellowstone National Park, and
scientists say it may be due for another eruption.
!wild fact!
• The largest volcanic eruption ever observed
was of Mount Tambora, on the island of
Sumbawa, in Indonesia. Its eruption in 1815
killed about 100,000 people. Indonesia is
thought to have the largest number of
historically active volcanoes – a total of 76,
according to the U.S. Geological Survey.
weird fact’s
• Hundreds of years ago, the Aztecs of Mexico
and the people of Nicaragua believed gods
lived in lava lakes. They would sacrifice
beautiful young girls to these powerful gods.
sad fact 
• During the past 400 years, nearly a quarter of
a million people have been killed as a direct
result of volcanic eruptions. Indirect
aftereffects such as famine, climate change,
and disease most likely have tripled that
number
What is a Volcano?
A Volcano is an opening (crack) in the crust
where lava reaches the surface
How does it happen?
• Volcanoes are generally found where tectonic
plates are diverging or converging
………………………..
Sidenote:
• (volcanoes are usually not
created where two tectonic plates slide past
one another…..this type of movement
causes…..???)
Plate Tectonics & Hotspots
The pulling apart
of plates, causing
molten
Divergent
plate
boundaries
The
pulling apart of
plates, causing
molten rock to
come to the top of
the mantle. Causes
mainly submarine
volcanic activity
and creates new
oceanic crust.
rock to come to
the top of the
mantle. Causes
mainly submarine
volcanic activity
and creates new
oceanic crust.
The c The
collision of
plates, causing
Convergent plate
boundaries
The collision
of plates,
causing
Subduction
or one plate
to submerge
beneath the
other late to
submerge
beneath the
other plate to
submerge
beneath the
other ollision
of plates,
causing
Subduction or.
Hotspots
Located away
from tectonic
plates, over
mantle plumes
where pipes
vent magma.
Volcanoes
formed over
hotspot go
dormant and
new ones are
formed when
plates move
overhead.
Divergent Plate Boundaries
Most divergent plate boundaries are at the bottom of the
oceans, causing most of the volcanic activity to be under
water, thus forming new seafloor.
Convergent Plate Boundaries
• When two plates (usually an oceanic and continental
plate) collide, causing the one plate to submerge
under the other plate (called subduction).
• In the case of oceanic-continental, a deep trench just
off shore is formed.
• When the thick magma, reaches the surface, a
volcano is formed.
• *This is what caused the typical Ring of Fire
volcanoes.*
Oceanic - Continental convergence
Continental - Continental convergence
Oceanic - Oceanic convergence
• In the theory of plate tectonics most of the
geological characteristics are explained by
tension (interaction) among plates. However,
some of most spectacular formations are
caused by "hot spots" which are situated far
from the edges of tectonic plates.
Hotspots
A hotspot is a place in the middle of a
tectonic plate where hot magma rises
(called a mantle plume) until it reaches the
crust. Magma then flows out.
Pacific Ring of Fire
• The Pacific Ring of Fire is an area of frequent
earthquakes and volcanic eruptions circling
the basin of the Pacific Ocean.
• Result of plate tectonics and the movement
and hitting of crustal plates.
Ring of Fire
Area where large numbers of earthquakes and volcanic
eruptions occur in a 40,000km horseshoe shape.
Contains 452 volcanoes, with over 75% of worlds active and
dormant volcanoes.
There are 3 types of Volcanoes
• Shield Volcano
• Cinder Cone Volcano
• Composite Volcano
Shield Volcano
Shield Volcano
• A gently-sloped volcano
(large volcano but not
very tall)
• built out of layers of
lava from lots of little
eruptions
Cinder Cone
• Most common
• Steep sides
• Made of cinders
(melted volcanic rock
that has cooled down)
Composite Volcano
• A tall volcano made of
many layers of cinders
and hardened lava
What kind of volcano is this?
Diamond Head is an eroded Cinder
Cone volcano
Early sailors mistakenly
thought shining calcite
crystals inside the rocks
were diamonds, leading to
the incorrect name.
Diamond Head formed
when hot magma rising up a
tube hit ocean water,
causing large explosions
that threw exploded magma
particles into a broad ring.
What kind of Volcano is this?
Mount Shasta is a composite volcano
Over the last 10,000 years,
Mt. Shasta has erupted on
average once every 800
years. During the 3,500
years the volcano has
erupted about once every
300 years. The most
recent eruption may have
occurred in 1786 A.D.
California
What kind of volcano is this?
Kohala is a shield volcano.
• Kohala is the oldest of
the subaerial volcanoes
that make up the Island
Of Hawaii. Kohala is
considered to be extinct
because it has not
erupted for 60,000
years.
Hawaii