Transcript Volcano Anatomy

Volcanoes
Questions
• Compare/contrast the 3 places volcanoes
occur:
– Divergent
– Convergent
– Hotspots
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What’s pyroclastic flow?
How can volcanoes effect life?
How can you predict volcanoes?
What was Mount St. Helens?
A reminder
• Magma: Melted rock
inside the Earth
• Lava: Melted rock
outside the Earth
• Rocks melt when the
pressure drops, or the
temperature rises
Volcanologists
• Volcanologist: A person
who studies volcanoes
– VERY dangerous work
• In 20 years, 23
volcanologists have been
killed
• Considering that there’s
only about 200-300
volcanologists worldwide,
that’s a pretty high rate!
Volcano Location
• Volcanoes occur at 3 places
– Divergent plate boundaries
– Convergent plate boundaries
– Hotspots
Divergent Plate Boundary
• Divergent plate
boundaries—
Tectonic plates that
move away from
each other
– Example: The Ring of
Fire in the Pacific
Ocean
Ring of Fire
• The Pacific Ring of
Fire: A series of
452 volcanoes
located in a
horseshoe shape
around the Pacific
Ocean
– Contains 75% of
the world’s active
and non-active
volcanoes
Ring of Fire continued
• Ring of Fire
– 90% of the world’s
earthquakes occur in the Ring
of Fire
• Active volcanoes generate lots
of earthquakes
– This is caused by the
subduction of tectonic plates
at convergent plate
boundaries
– What an erupting underwater
volcano looks like
United States Ring of Fire
• In the United
States:
– There’s 20 major
Ring of Fire
volcanoes on the
West Coast
Convergent Plate Boundary
• Convergent plate
boundaries—Tectonic
plates that move
towards each other.
• Generally form
volcanoes in
subduction zones
• Creates some of the
most explosive
volcanoes
– Example: Mount St.
Helens
Hotspot
• Hotspot—Volcanoes
that form in the
middle of tectonic
plates
– Might make lots of
volcanoes or islands
as the lithosphere
moves away from the
hotspot
– Generally not as
explosive as other
volcanic locations
– Examples: Hawaii,
Yellowstone
Volcano Effects
Volcanic effects on Earth
– Volcanic eruptions can be seen on land and in the
air
• They build mountains
• They create plateaus
Pyroclastic
Pyroclastic flow: Ash, dirt, rocks, lava, and other
flaming debris that is thrown from a volcano
during an explosive eruption
Pyroclastic Effects
Pyroclastic Effects
• Pyroclastic material destroys
the ground
• Ash + water= cement-like
material
• It collapses buildings because
of the added weight
• Dams up rivers, which create
floods
• Kills crops and livestock
Climate Changes
Climate Effects
• Ash and escaping gases change climate
– Ash blocks out sunlight, which creates a
(temporarily) cooler climate
• Wetter, cooler summers
• Colder, snowier winters
• Prettier sunsets!
Prediction
Predicting Volcanoes
• There is no sure-fire way to
predict a volcano
– Measure small earthquakes
• This indicates moving magma
and shifting rocks underground
– Measure slope of volcano’s
cone
• Look for bulges
– Measure volcanic gases
• More gases=possible eruption
Mount St. Helens
• A subduction zone volcano
in Washington
• Erupted on May 18th, 1980
after being quiet for 123
years
• 57 people killed
• There would have been more
fatalities, but it erupted on a
Sunday!
• Over $2 billion in damages
• Most expensive and
deadliest volcano ever in the
US
Ash from Mount St. Helens
The actual eruption
One hour after the blast
Ash clouds the day after
2 weeks after the blast
Car buried in ash
Mudflows 6 feet tall
Trees blown over by the force of
the eruption, 5 miles away
8 miles from the blast site
Dashboard of a truck 9 miles from
the blast site
Minor eruption 2 months after the
initial blast