Download Volcanoes

Volcanoes
And Plate Tectonics
objectives
• F.3.1.1. Identify where most of
Earth’s volcano regions are located
and explain why they are found in
these areas.
• F.3.1.2. Explain how a hotspot
volcano forms and give an example
of one.
Definitions
• A volcano is a weak spot in Earth’s crust where
magma is able to come through and reach the surface.
• Magma is a combination of molten (melted) rock,
gases and water.
• Once it reaches the surface it is called lava. This does
not mean the substance has changed, it hasn’t. It just
means it has reached the surface.
• Lava cools to from new rock.
Volcanoes and plate
boundaries
• Volcanoes most often form along
plate boundaries. There are
exceptions but usually they are
found where plates meet.
• The Ring of Fire is a long belt of
volcanoes that stretch all the way
around the Pacific Ocean.
Ring of fire
Most volcanoes
form along
Convergent Boundaries
Divergent Boundaries
Divergent boundaries
• Many volcanoes
form along mid
ocean ridges under
water and along rift
valleys on land. Can
you name a famous
mid ocean ridge?
• The Mid Atlantic
Ridge
Divergent boundaries
• Divergent
boundaries
on land are
called rift
valleys.
Convergent Boundaries
• Many volcanoes
form along
convergent plate
boundaries where
the older, more
dense plate is being
subducted back into
the mantle.
Oceanic to oceanic
• Where an older, more dense oceanic
plate subducts under a newer less dense
plate, the rock can melt to produce
magma. The less dense magma and
superheated water vapor become less
dense than the surrounding rock. What
will this less dense material do?
• Rise through the crust.
Oceanic to oceanic
• This type
of
subduction
can often
produce an
Island Arc.
Island arc
Island arc
Oceanic to continental
Oceanic to
continental
This type of convergence
created the Andes
Mountains in South
American and the volcanic
mountains in the Pacific
Northwest of the United
States.
Mt. St. Helens During
Mt. St. Helens
Before Eruption
After Eruption
Hot spot volcanoes
• Hot Spot Volcanoes
form above a hot
spot in the mantle
where convection
currents bring
superheated magma
from the core to the
surface.
Hot spot volcanoes
Hawaii
Hawaii
Hawaii
Hawaii From space
Hawaii Bathymetry
f.3.1.1.
• Where do most volcanoes form?
• Most of Earth’s volcanoes form
along convergent and divergent
plate boundaries.
F.3.1.1.
• Why do they form along plate
boundaries?
• These are places where the crust
opens up to allow magma up or
where melting rock and super
heated water create buoyant
pressure from below.
f.3.1.1.
• What is the
ring of fire?
• It is a volcano
belt that
surrounds the
Pacific Plate.
f.3.1.2
• Some scientists
believe this to
be a hot plume
of the molten
metal from the
outer core
rising through
the mantle.
f.3.1.2.
• A plume of hotter
material rises
through convection
currents to just
beneath the crust
and causes a breach
to form in the crust
that allows magma
to push through to
the surface.
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