Hotspots, Shield Volcanoes
and Supervolcanoes
SMS 6th Grade Science
Mrs. Clark
Not necessarily on the
edge of plate boundaries!
Shield Volcanoes are
formed by ‘hotspots’
“What is a hotspot?”……
A hotspot is…
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•
•
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A rising plume of hot mantle material
It melts through the crust
Like a blow torch
Often lies in the middle of a plate
Draw the hotspot and resulting
shield volcano (please)
Shield Volcano Characteristics
• Thin layers of lava build on other thin
layers
• Lava is thin and runny
• Lava pours out in rivers and lakes
• Eruptions are quiet and non-explosive
• Wide and gently-sloping
Examples: Hawaii Islands are
formed as the Pacific Plate moves
over a fixed hot spot
Mauna Loa (Hawaii)
Belknap Crater (Oregon)
Newberry Volcano (Oregon)
Its so flat that you probably
wouldn’t even suspect it is a
volcano!
Where is this shield volcano???
First person to raise their hand with the correct answer gets a piece of candy!
This is Olympus Mons, it is on
Mars!
Olympus Mons
• 624 km (374 mi) in
diameter – that is like
driving from
Sherwood to
anywhere for 6 hours!
• 25 km (16 mi) high
• It is 100 times larger
than Mauna Loa on
Earth.
Supervolcanoes
(what the heck are they?)
• erupt rarely ……
• but with a force at least 1000 times that of
ordinary volcanoes
• caused by hot spots under CONTINENTAL
CRUST
• Yellowstone is one of a few known
examples!
Yellowstone Supervolcano
• In recent years it has been discovered that
Yellowstone is one of a few known examples of
a supervolcano.
• A large part of the national park area is a giant
crater formed by the last explosion 640,000
years ago.
• It is so large that it can only be seen from space.
• It explodes regularly every 600,000 years - in
between it is quiet, now it is 40,000 years
overdue.
Yellowstone Supervolcano from space…..
Yellowstone Supervolcano …..
(you can see the tracks over the continental crust as the N. American
plate has moved)
Yellowstone Supervolcano
• Modern humans did not exist last time this
exploded but its effects are known - a herd
of fossilized rhinos were found choked to
death under the ash layer a thousand
miles away.
• Try to imagine 1000 volcanoes erupting in
the same place at the same time!
The Last Time Yellowstone
Supervolcano Erupted….
(the brown area was covered with ash)
Yellowstone Supervolcano
Most of America was buried under several feet of
volcanic ash - and there were vast amounts of choking
sulfurous gases. This has been going on for at least
10,000,000 years. The craters (calderas) from the last
3 eruptions have been identified and date from
600,000 years, 1,200,000 years and 1,800,000 years.
Yellowstone Supervolcano
There is a giant blob of red hot magma 8,000
meters below Yellowstone, it has been building
up since the last eruption and is fed from a hot
spot below. It is now 50 Km long, 30 Km wide
and 10 Km deep and is full of dissolved gasses
at enormous pressure.
Yellowstone Supervolcano
The gases are the cause of the explosion that
occurs once the eruption is underway - the magma
pools below the surface under great pressure.
When the steady build up of pressure finally forces
a way through to the surface the effect is similar to
removing the cork from champagne - the gases
suddenly leave the liquid they were dissolved in
and blow the liquid out of its container. Once an
eruption starts it will accelerate until the whole pool
of magma explodes, throwing at least 1000 cubic
kilometers of hot material high into the atmosphere.
Some Scientists believe that this is likely to
happen soon, the area north of the lake has
bulged upwards by almost a meter in 50
years. One side of the lake is creeping into
the forest as the land rises. This type of
rapid change cannot continue for long
without something giving way, every year
there are hundreds of small earthquakes.
Earth Science Journal Pages 10 and 11
• Page 10: Title ‘Stratovolcanoes’
• Draw a colored diagram of a stratovolcano and list 5 facts
(from your notes) about it underneath your diagram.
• Below that, give 3 examples of stratovolcanoes
• Page 11: Title ‘Shield Volcanoes’
• Draw a colored diagram of a Shield Volcano and list 5 facts
(from your notes) about it underneath your diagram.
• Below that, give 3 examples of shield volcanoes