Introduction to “supervolcanoes” Watch the short clip about supervolcanoes. Take particular note of how they are created. V8Y V8Y

Distribution of supervolcanoes

Formation of a supervolcano at a hotspot 1)Number the statements on your sheet in the correct order to explain how a supervolcano forms. 2)Split the explanation into three parts a)Before the eruption b)During the eruption c)After the eruption Extension: If you finish have a go at drawing some ……. ….diagrams to accompany the explanation.

Before an eruption… Magma rises up through cracks in the crust to form a large magma basin below the surface. The pressure of the magma causes a circular bulge on the surface several kilometres wide.

During an eruption… The bulge eventually cracks, creating vents for lava to escape through. The lava erupts out of the vents causing earthquakes and sending up gigantic plumes of ash and rock. As the magma basin empties, the bulge is no longer supported so it collapses – spewing up more lava.

After an eruption… When the eruption is finished there’s a big crater (called a caldera) left where the bulge collapsed. Sometimes these get filled with water to form a large lake (e.g. Lake Toba in Indonesia).

Characteristics of a supervolcano TASK: Copy down the correct characteristics Emit at least 1000km 3 of material Looks like a typical volcano with characteristic cone shape Flat Cover a large area Erupt regularly Have a caldera (depression marking the collapsed magma chamber)

Yellowstone Known to have erupted 630,000, 1.3 million and 2 million years ago 1,000 times bigger than Mt St Helens eruption Popular with tourists due to its unique landscape

Another eruption at Yellowstone? There is evidence that the magma beneath Yellowstone is shifting. The caldera is bulging up beneath Lake Yellowstone. Signs of increasing activity in some geysers (geothermal feature where water erupts into the air under pressure). Ground has risen 70cm in some places.

Scale: 450km N-S 600km wide

Effects of a supervolcano Thousands of km 3 of rock, ash and lava spewed out Thick cloud of super heated gas and ash flow out at high speed, killing, burning and burying everything it touches Ash shoots out kilometres into the air blocking sunlight over whole continents Mini ice age triggered Possible global famine Ash settles over hundreds of km 2 Flooding TASK: Which of these do you think are real? Why? Why not?

Extent of Yellowstone ash from last eruption…

Effects of Yellowstone timeline - Create a timeline in your exercise book. - As you watch the video clip add predicted impacts of the potential eruption to your timeline.

Immediate Everything in 100 mile radius incinerated Cloud of poisonous gases races across US – 30 mins to cover Wyoming and cross into S. Dakota Evacuation impossible once cloud of ash has hit Ash 8ft deep and heavier than snow Ash clogs internal combustion engines and people are stranded Emergency services unable to reach people People outside suffocated almost immediately by toxic gas Buildings collapse due to weight of ash

Within 1 week Ash would immobilise entire country 2/3 rd USA covered by ash Ash washed into rivers turns to mud, blocks channels and causes massive flooding in mid- west Planes couldn’t fly and vehicles couldn’t drive Looting ‘dog eat dog’ post-apocalyptic situation

A few weeks later Temperatures plummet as gas and ash block incoming sunlight Sulphuric gases & ash spread around world Long term Mini ice age Global harvest failure  famine? Civilisation greatly changed

Your task Log on to this site – it is the story of Yellowstone. /high/index.html /high/index.html Read the story (I recommend switching off the sound!) & add to your notes any key facts about the tectonic aspects of the caldera. E.G, what is happening to the lake & why? What is a hotspot, a fumarole, a geyser?