Transcript Volcanoes and Earthquakes

Volcanoes
March 2012
Eruption Types
• 1. Explosive
• ejects gases, ash,
and pyroclastics shot
into air and across
ground
• caused by lots of
water and gases
trapped in magma
Eruption Types
• 2. Nonexplosive
• lava runs down the
slopes of the volcano
Forming Volcanoes
1. Subduction Zone
-most volcanoes
formed this way
(plate boundary)
-one plate melts as it
goes under the
other, magma rises
upward
• http://www.classzone.com/books/earth_sci
ence/terc/content/visualizations/es0902/es
0902page01.cfm?chapter_no=visualizatio
n
Forming Volcanoes
2. Hot Spots
-located
in middle of
plates, not
boundary
-very thin crust
allows magma to
rise up, volcano
forms, crust
moves, starts over
• http://www.wwnorton.com/college/geo/ege
o2/content/animations/2_6.htm
Types of Volcanoes
1. Shield Volcano
• Nonexplosive eruptions
– Layer upon layer of
hardened lava
• Gradual sloping sides,
but can be enormous in
size
Mt Etna and Mauna Kea
Mt. Etna in Italy-notice how broad it is;
this volcano is south of Vesuvius on the
island of Sicily
Mauna Loa-part of Mauna Kea,
which is the largest mountain on
Earth when measured from the
ocean floor
Types of Volcanoes
2. Cinder Cone Volcano
• explosive eruptions
– Layer upon layer of
pyroclastics
• Erode quickly
because they are not
“glued” together by
lava
Paricutin-Mexico
Paricutin erupting at night.
The volcano ejected materials from
a hole in a cornfield until it covered
a whole town. The tower from this
church is all that is left of town.
Types of Volcanoes
3. Composite Volcano
(aka: Statro volcano)
• Made from explosive
and non-explosive
eruptions
• Alternating layers of
lava and pyroclastics
Stratovolcanoes
Mt Vesuvius, Italy- notice all of the
buildings and people that surround the
volcano.
Mt. St. Helens, May 18, 1980
Predicting Eruptions
• Volcanologists
look for:
1. Faults – the Earth
cracks when pressure
builds up
2. Gases – content and
amount of gases
3. Rockfall (RF) –
landslides/deformation
4. Volcano Tectonics (VT)
– earthquakes in
volcano
Volcanoes and Global Cooling
• Explosive eruptions have released enough
gases and ash into the atmosphere to effect
weather globally by blocking the sun’s heat
Picture Time
This is some of the damage from Mt. St. Helens in May of
1980. That is volcanic ash on the right, not snow.
Iceland, Heimaey
The people of Iceland live in very close proximity to
many volcanoes.
Iceland-Cold with Volcanoes
Volcanoes UNDER the
glaciers melt the ice and
make glacial lakes.
This is a cinder cone volcano;
it just happens to be quiet and
snowy for the moment.
Surtsey, Iceland
Surtsey appeared off
the coast of Iceland
in 1963. In four
years, the island was
1 sq. mile and had
elevations of 560
feet!
Mt. Etna, Italy
This is just a really cool picture of lava from Mt. Etna.
Pacific Ring of Fire
Pacific Hot Spots