Download How and Where Volcanoes Form

How and Where
Volcanoes Form
Quick Review
• What is magma?
• Why does magma rise?
• At what kind of plate tectonic boundary/
boundaries do we find volcanoes?
• Why do volcanoes form here?
Definition of Volcano
• A. Volcano: Both an opening in
Earth’s crust through which molten
rock, gases and ash erupt and the
landform that develops around this
opening
B. Magma Formation
1. Decreasing pressure can lower the
melting temperatures of materials in the
asthenosphere (ex. Rift valley/mid-ocean
ridge)
2. Increasing temperatures can cause
materials in the asthenosphere to melt.
(ex. Hot spot)
3. Increasing water in the asthenosphere
can lower melting temperatures (ex.
Subduction boundaries)
C. Rise to the Top
1. Magma tends to rise to the surface
because it is less dense than the solid
material surrounding it
2. The traits of the magma and the rate
at which is rises depends on the
amount of silica
3. Higher silica, thicker
magma, more explosive
Volcano Location
Reason
Volcano
Formation
Special Notes
Examples
Row 1
Volcano Location
Subduction
Boundary
Divergent
Boundary
Hot Spot
Reason
Volcano
Formation
Special Notes
Examples
Row 2
Volcano Location
Reason
Subduction
Boundary
Collision between
Oceanic/Continental
Or Oceanic/Oceanic
High temperature + low
pressure = lots of
magma
Hot molten magma
from deep within
the Earth rises up
through the crust
and reaches the
surface
Divergent Boundary
Hot Spot
Volcano
Formati
on
Special
Note
s
Examples
Row 3
Row 4
Row 5
Special Notes
Examples
Volcano Location
Reason
Volcano Formation
Subduction
Boundary
Collision between
Oceanic/Contine
ntal
Or Oceanic/Oceanic
Divergent Boundary
High temperature +
low pressure =
lots of magma
Hot Spot
Hot molten magma
from deep within
the Earth rises up
through the crust
and reaches the
surface
On plate that
does not
sink
Where the
plates
separate
In the middle
of plates
away from
plate
boundaries
Row 4
Volcano Location
Reason
Volcano Formation
Special Notes
Subduction Boundary
Collision between
Oceanic/Cont
inental
Or
Oceanic/Oce
anic
On plate that does
not sink
Divergent Boundary
High temperature
+ low
pressure =
lots of
magma
Where the plates
separate
Hot Spot
Hot molten
magma from
deep within
the Earth
rises up
through the
crust and
reaches the
surface
In the middle of
plates away
from plate
boundaries
oceanic/oceanic,
forms
“VOLCANIC
ARC”
Most of these
volcanoes are
underwater
Hot spots do not
move, but the
crust does
Examples
Row 5
Volcano Location
Reason
Volcano
Formation
Special Notes
Examples
Subduction
Boundary
Collision between
Oceanic/Continental
Or Oceanic/Oceanic
On plate that
does not
sink
oceanic/ocean
ic, forms
“VOLCA
NIC
ARC”
O/C: Cascades
in
California
O/O: Aleutians
in Alaska
Divergent
Boundary
High temperature + low
pressure = lots of
magma
Where the
plates
separate
Most of these
volcanoes
are
underwat
er
Mid-ocean
ridge,
Iceland
Hot Spot
Hot molten magma from
deep within the Earth
rises up through the
crust and reaches the
surface
In the middle of
plates away
from plate
boundaries
Hot spots do
not move,
but the
crust does
Hawaiian
Islands,
Canary
Islands,
Yellowstone