Download Volcanoes

Eruptions and Forms of
Volcanoes
10.1 Volcanoes and Earth’s
Moving Plates
• Most active volcano: Kilauea
Located in Hawaii
• Magma formed: Heat and pressure
cause rock to melt
• What causes magma up? It is less dense
than surrounding rock.
Divergent boundaries:
plates move apart
Ex: Mid Atlantic Ridge
Convergent boundaries:
plates move together
Ex: Himalayas
Pacific Ring of Fire- the area around the
Pacific Plate where earthquakes and
volcanoes are common
Hot spot- areas in the
mantle that are
hotter than their
surroundings
Ex: Hawaiian Islands,
Yellowstone
National Park
10.2 Energy from Earth
How does geothermal energy produce
electricity?
• Heat and energy from magma is used
to boil water to produce steam used to
generate electricity.
Used in:
California, Nevada,
Utah, Hawaii
3 benefits of using geothermal
energy:
1. Reduction in oil spills on coastlines
2. No mine waste or radioactive waste
3. Reduction in pollutants from burning
fossil fuels
2 types of geothermal energy:
• Magma- molten rock deep inside Earth
• Hot dry rock (HDR)- water is pumped
into the cracks in rock- heated then
used to create steam
• Which type is more available? Hot dry
rock
Why? Temperatures increase with depth into
Earth
• Which type of geothermal energy
produces fewer carbon dioxide emissions?
Hot dry rock
• Why is HDR not used more?
It is too expensive
1. 2 important factors that determine
whether a volcano will be
explosive or quiet.
1.) the amount of gases
trapped in magma.
2.) the composition of the
magma.
2. Basaltic magmas generally
produce quiet eruptions.
Why?
Basaltic magma contains
less silica and is less
viscous (sticky).
Example: Hawaiian Islands
2. Granitic magmas generally
produce explosive eruptions.
Why?
Granitic magma contains more
silica and is more viscous
(stickier).
Example: Mount Saint Helens
Another factor that causes
granitic magma to be
explosive is the high water
vapor content.
3. Andesitic magma has
medium silica content
(medium viscosity)
Andesitic volcanoes are
explosive.
A. Composite
(stratovolcano)
B. Cinder Cone
C. Shield Volcano
laccolith
sill
dike
magma
batholith
1. Batholith – largest
intrusive rock bodies.
(greater than 100 km)
How? Form when a large
plume of magma cools
underground.
dike – magma squeezes into
a vertical crack.
sill – magma squeezes
between horizontal rock
layers.
Volcanic neck – weathering &
erosion remove the sides of a
volcano leaving the solidified
vent.
5. Caldera – when the top of a
volcano collapses after a large
eruption.