Download 5.5 and 5.6 Volcanoes ppt

Volcanoes and
Plate Tectonics
What is a volcano?
 Volcanoes
are weak spots in the crust
where magma rises to the surface.
Location of Volcanoes
 Volcanic
belts form along the plate
boundaries.
 Volcanoes
Fire
occur in belts like the Ring of
Location of Volcanoes
 Most
volcanoes
occur along
diverging plate
boundaries or
in subduction
zones.
Volcanoes at Diverging Plate
Boundaries
 Volcanoes
form at the mid-ocean ridge
underwater
Volcanoes at Converging Plate
Boundaries
 Volcanoes
form in subduction zones
-
Two oceanic plates collide
-
An oceanic plate and continental plate
collide
Volcanoes at Converging
Boundaries
 If
subduction zone involves two pieces of
oceanic crust, volcanoes are created
 These
volcanoes create a string of islands
called an island arc
 If
Volcanoes at Converging
Boundaries
subduction zone involves oceanic and
continental crust, volcanoes are created
on land.
Hot Spot Volcanoes
 Hot
spot is an area where magma melts
through the crust like a blow torch
 Hot
spots are not often at plate
boundaries
Hot Spot Volcanoes
 Hot
spots volcanoes can be created in
the ocean floor
 Hawaii
Hot Spot Volcanoes
 Hot
spots can form under continents
 Yellowstone
National Park
Inside A Volcano
 Draw
the picture
 Label the parts
 Add the central
vent, the side
vent, and the pipe
A Volcanic Eruption
 Did
you know that dissolved gases are
trapped in magma? These dissolved gases
are under great pressure. When the
volcano erupts, the force of the
expanding gases pushes magma from the
magma chamber through the pipe until it
flows or explodes out of the vent.
Two Types of Volcanic
Eruptions
 Explosive
eruptions: magma is high in
silica and thick and sticky. This magma
builds up in the pipe and plugs it like a
cork. When enough pressure builds, it
explodes.
 Quiet eruptions: magma is hot or low in
silica and thin and runny. The gases in the
magma bubble out gently. This type
formed the Hawaiian Islands.
Volcano Hazards
 Both
types can cause tremendous
damage. Quiet eruptions allow lava to
flow from vents, setting fire to everything
in its path. Explosive eruptions allow
volcanoes to belch out hot rock and ash
that produces fast-moving clouds that
rush down the side of the volcano called
pyroclastic flow.
Stages of Volcanic Activity
 Active:
a volcano that is erupting or has
shown signs that it may erupt in the near
future
 Dormant (sleeping): a volcano that may
awaken in the future
 Extinct: a volcano that is unlikely to ever
erupt again.