Hotspots, Shield Volcanoes Hotspots, Shield Volcanoes and Supervolcanoesand Supervolcanoes

SMS 6SMS 6thth Grade Science Grade ScienceMrs. ClarkMrs. Clark

Not necessarily on the Not necessarily on the edge of plate boundaries!edge of plate boundaries!

Shield Volcanoes are Shield Volcanoes are formed by ‘hotspots’formed by ‘hotspots’

““What is a hotspot?”……What is a hotspot?”……

A hotspot is…A hotspot is…

• 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 Draw the hotspot and resulting shield volcano (please)shield volcano (please)

Shield Volcano CharacteristicsShield 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 Examples: Hawaii Islands are are formed as the Pacific Plate moves formed as the Pacific Plate moves

over a fixed hot spotover a fixed hot spot

Mauna Loa (Hawaii)Mauna Loa (Hawaii)

Belknap Crater (Oregon)Belknap Crater (Oregon)

Newberry Volcano (Oregon)Newberry Volcano (Oregon)Its so flat that you probably Its so flat that you probably wouldn’t even suspect it is a wouldn’t even suspect it is a

volcano!volcano!

Where is this shield volcano???Where is this shield volcano???First person to raise their hand with the correct answer gets a piece of candy!First person to raise their hand with the correct answer gets a piece of candy!

This isThis is Olympus Mons Olympus Mons,, it is on it is on Mars!Mars!

Olympus MonsOlympus 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.

SupervolcanoesSupervolcanoes(what the heck are they?)(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 SupervolcanoYellowstone 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 from space…..

Yellowstone Supervolcano …..Yellowstone Supervolcano …..(you can see the tracks over the continental crust as the N. American (you can see the tracks over the continental crust as the N. American

plate has moved)plate has moved)

Yellowstone SupervolcanoYellowstone 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 The Last Time Yellowstone Supervolcano Erupted…. Supervolcano Erupted….

(the brown area was covered with ash)(the brown area was covered with ash)

Yellowstone SupervolcanoYellowstone SupervolcanoMost of America was buried under several feet of Most of America was buried under several feet of

volcanic ash - and there were vast amounts of choking volcanic ash - and there were vast amounts of choking sulfurous gases. This has been going on for at least sulfurous gases. This has been going on for at least

10,000,000 years. The craters (calderas) from the last 10,000,000 years. The craters (calderas) from the last 3 eruptions have been identified and date from 3 eruptions have been identified and date from

600,000 years, 1,200,000 years and 1,800,000 years.600,000 years, 1,200,000 years and 1,800,000 years.

Yellowstone SupervolcanoYellowstone Supervolcano

There is a giant blob of red hot magma 8,000 There is a giant blob of red hot magma 8,000 meters below Yellowstone, it has been building meters below Yellowstone, it has been building up since the last eruption and is fed from a hot up since the last eruption and is fed from a hot spot below. It is now 50 Km long, 30 Km wide spot below. It is now 50 Km long, 30 Km wide

and 10 Km deep and is full of dissolved gasses and 10 Km deep and is full of dissolved gasses at enormous pressure. at enormous pressure.

Yellowstone SupervolcanoYellowstone Supervolcano

The gases are the cause of the explosion that The gases are the cause of the explosion that occurs once the eruption is underway - the magma occurs once the eruption is underway - the magma

pools below the surface under great pressure. pools below the surface under great pressure. When the steady build up of pressure finally forces When the steady build up of pressure finally forces a way through to the surface the effect is similar to a way through to the surface the effect is similar to

removing the cork from champagne - the gases removing the cork from champagne - the gases suddenly leave the liquid they were dissolved in and suddenly leave the liquid they were dissolved in and blow the liquid out of its container. Once an eruption blow the liquid out of its container. Once an eruption

starts it will accelerate until the whole pool of starts it will accelerate until the whole pool of magma explodes, throwing at least 1000 cubic magma explodes, throwing at least 1000 cubic

kilometers of hot material high into the atmosphere.kilometers of hot material high into the atmosphere.

Some Scientists believe that this is likely to Some Scientists believe that this is likely to happen soon, the area north of the lake has happen soon, the area north of the lake has

bulged upwards by almost a meter in 50 bulged upwards by almost a meter in 50 years. One side of the lake is creeping into years. One side of the lake is creeping into

the forest as the land rises. This type of the forest as the land rises. This type of rapid change cannot continue for long rapid change cannot continue for long

without something giving way, every year without something giving way, every year there are hundreds of small earthquakes.there are hundreds of small earthquakes.

Earth Science Journal Pages 10 and 11Earth 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