Transcript Hawaiian Hot Spots

How come the
most volcanic
place on Earth is
nowhere near a
plate margin?
Hotspots
LO: To be able to explain how
volcanoes are formed at hotspots
Main areas of hot spot activity
globally
TOPS Top 10 Geography in conjunction
with www.sln.org.uk/geography
Hawaiian Hot Spots
http://www.youtube.com/wat
ch?v=bYv6V5EJAKc
Hotspots are areas in the lithosphere that
are underlain by unusually hot magma.
This heat causes partial melting of the
lithosphere, eventually leading to
volcanic activity. The Hawaiian
Islands are a classic example of a
volcanic grouping formed over one hot
spot.
• Over thousands of years, as the Pacific
Plate inched its way in a northwest
direction, the stationary hot spot
underneath the plate successively
created volcanoes above it. Several of
these volcanoes reached the ocean’s
surface, forming the Hawaiian Islands.
Photos of Active volcanoes in Hawaii
taken November 4th 2010
Hot spot volcanoes
In the animation above, why are the volcanoes to the left of the
‘hot spot’ extinct?
Hawaii
Many volcanoes but only 5 are active.
The summit of Mount
Everest is higher above sea
level than the summit of
any other mountain, but
Mauna Kea is the tallest
when measured from base
to summit.
Why do we have volcanoes here
Volcano
Last
eruption
Loihi
1996 (A.D.)
Kilauea
Ongoing
since 1983
(A.D.)
1984 (A.D.)
12
1800 to 01
(A.D.)
1790
40
Mauna Loa
Hualalai
Haleakala
Distance
from Loihi
km
0
14
182
Why is Hawaii a chain of Islands?
As the plate continued to move, volcanoes,
embedded in the plate, travelled away from the
source of magma and eventually became extinct.
This hot spot still continues to create new
volcanoes. Thus, the islands are progressively
younger from the northwest to the southeast.
Several volcanoes in the chain are still quite active,
and new underwater volcanoes are forming to the
southeast of Hawaii as the Pacific Plate continues to
move over the hot spot.
Height of the islands?
Taller islands are the youngest ones.
Older islands have reduced in size due to weathering and erosion
Lets look at the evidence
• Hawaiian Islands are in the centre of the
Pacific plate
• Islands are smaller as we move away from
Loihi
• Volcanoes decrease in activity away from
Loihi
• Islands increase inCan
age
away from Loihi
you explain the reasons for the
formation of the Hawaiian islands?
• The Hawaiian volcanoes were produced by the Hawaiian hot spot, a
localized source of high heat in the mantle which is presently under
the Big Island of Hawaii.
Heat from this hotspot
produced a persistent
source of magma by
partly melting the
overriding Pacific
Plate.
The magma, which is lighter than the surrounding solid rock,
then rises through the mantle and crust to erupt onto the
seafloor, forming an active seamount.
Summary notes
• Not on plate boundaries.
• Unusually hot magma plumes in the mantle erupt through the crust.
• This creates seamounts which are volcanic mountains beneath the sea.
Seamounts can rise above the ocean surface to create islands.
• The Hawaiian Island chain formed as the Pacific crustal plate moved over a
stationary source of magma or hotspot.
• There are many volcanoes on the Hawaiian islands, however, only a few are
active. When volcanoes move off the hotspot they lose their source of magma
and become extinct.
• Volcanoes at the hotspot include:
• Loihi – a submarine volcano that is continuing to grow in size.
• The Big Island of Hawaii is at the hotspot and has several active volcanoes e.g.
Mauna Loa and Kilauea.
Example of a hotspot exam question
(4)
Mark scheme
Example of what another student
wrote and how the examiner marked
them!