Hot Spots
Learning Objectives
To be able to describe and explain
the features of hot spots
To describe a case study of hot spot
volcanoes
Key Terms
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Hotspot
Magma plume
Basalt
Volcanic islands
Lithosphere
Key Ideas
• Not all volcanic activity can be related to
present day active plate margins
• The Pacific Ocean shows a number of subparallel chains of volcanic islands which run
diagonally across the Pacific plate
• These islands are all shield volcanoes built
up of basaltic lavas
• The basalt that makes up these islands
contain significantly more potassium and
sodium than the basalts which make up the
ocean crust.
• This suggests that while the mantle forms
the source for both these rocks suites,
there must be a different mechanism
involved in their formation
• The formation of these volcanic islands is
related to the occurrence of long-lived,
stationary hot spots within the mantle
How do they form?
• Hot spots provide localised intensive heat sources
(mantle plumes) - which partly melt the overlying
plate, creating a continuous magma source;
• Magma is lighter than the solid lithosphere and
rises up, erupting at the surface;
• Where crust is thin above a hot spot, this provides
further opportunity for magma to escape as
volcanic eruption;
• Lava builds up over time, eventually creating an
island, above the present sea-level.
• http://www.youtube.com/watch?v=jZdeavURhk8
• http://www.youtube.com/watch?v=WZepOlsRFxQ&f
eature=related
• http://www.youtube.com/watch?v=yTrWhwz9HzE
Examples of Hot Spots
• HAWAIIAN ISLANDS (series of volcanic
islands) - in middle of Pacific Plate
•
YELLOWSTONE NATIONAL PARK - USA
- hotspot located in interior of a continental
plate (North American Plate)
HAWAIIAN ISLANDS
What direction is the
Pacific Plate moving?
Here the bigger Island
of Hawaii is currently
over the hot spot
YELLOWSTONE NATIONAL PARK
Yellowstone appears to
be over a continental
hot spot that has
produced a chain of
volcanoes as the North
American Plate moves
southwestward over
the hot spot
YELLOWSTONE NATIONAL PARK
Your turn
• Complete the ‘fill the gap’ task on the
sheet
• Draw a labelled diagram to show how
hotspots and volcanic islands form
• Complete the case study task sheet on
Hawaii