Download Hot Spot Volcanoes

Where and How Do Volcanoes Form?
Where:
1. Almost all volcanoes are found @ Plate Boundaries and are made by
plate motions (Subduction, SFS, Rifting)
• Most of those volcanoes are found along the EDGE OF THE PACIFIC
PLATE– a subduction zone called “The Ring of Fire”
2. Hot spots: May or may/not be plate boundaries
Ring of Fire = Edge of the Pacific Plate.
Most of the worlds volcanoes are found here due to
SUBDUCTION of the pacific plate.
Melting Rock to Make Magma
1. Heat Melts Rock
Heat from mantle; Heat from friction of grinding plates; heat
from magma that intrudes into crust from other locations
2. Decrease Pressure on Rock
Decompression Melting: When pressure is reduced rock can
melt at lower temps. Pressure depends on depth. As hot rock
rises; it melts because there is less pressure.
* Rock deep in crust should melt; but is solid because of
pressure)
3. Add Water: “Wet” rock melts at lower temps.
Subduction drives water out of the subducting rock
(metamorphic change). “Dewatering the slab” lowers the
temperature of rock above.
3 Ways Volcanoes Form
1. Subduction Zones (Convergent Plate Boundaries)
(Ring of Fire): Water in minerals leaves rock of subducting plate; this
lowers melting temp. of crust above; crust melts and builds volcanoes.
2. Rifting & Sea Floor Spreading (Divergent Plate
Boundaries)
(African volcanoes & Iceland’s volcanoes): Magma rising
from below pushes plates apart and builds volcanoes.
3. Hot Spots – can be in the middle of a plate
(Yellowstone, Hawaii)
– a region of active magma under a plate.
This active magma
forces its way through weaknesses in the crust to form volcanoes; Deep magma
source.
Hot Spots
The Hawaiian Islands were formed as
seamounts grew over hot spots in the
Pacific.
Hot Spots Around the World
Hot Spot Volcanoes
Hot Spot Volcanoes
 Hot spot stays in the same place while the plate moves above.