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What are some examples of location of hot spots?

- the Deccan Traps in India
- the Hawaiian islands
- Yellowstone supervolcano


What is the main theory of how hot spots form?

1. Intensive radioactivity in the Earth's interior creates upwelling lava known as a magma plume
2. The plume pushes upwards and plastic rocks in the asthenosphere become molten, melting the crust above. This lies in a fixed position
3. The plate moves over the hot spot and the upwelling magma creates a succession of volcanoes that migrate with the plate


How do volcanic island chains form?

- the plume lies at a fixed position
- the ocean floor moves over this hot spot and the upwelling magma causes a steady succession of new volcanoes which forms a chain of volcanic islands


What is an example of a volcanic island chain, where is it located and how fast does the plate move per year?

- Hawaii
- the hot spot is at a fixed position under the Pacific plate
- the Pacific plate is moving quite fast here at around 5 inches per year


How do supervolcanoes form?

- a column of magma rises through a vent in the Earth's crust (if at a hot spot, this is continental crust)
- the magma becomes stuck and pools, melting the surrounding rock for thousands of years
- over these years, pressure builds up, causing an eruption which drains the magma lake of melted rock so the land above collapses, forming the caldera of a supervolcano


What are some general facts about Yellowstone supervolcano?

- close to 100km across in size
- small eruptions have occurred every 20 to 3000 years
- the cycle of caldera eruptions is estimated to be around every 600,000 to 700,000 years but it is difficult to predict when the next one will be


Why is Yellowstone there?

Beneath Yellowstone there is a hot spot which settled 2 million years ago there


What are some possible warnings of another Yellowstone eruption?

- since 1996 there has been an uplift in land level which could be due to small injections of magma pushing up the land or gas build up
- in 1999 a group of scientists found a bulge under Yellowstone lake floor which could warn an explosion
- Yellowstone has 5000km of eruptible material


What would be the consequences of a Yellowstone eruption?

- columns of ash would be ejected 10s of km in the air
- would kill thousands of people due to pyro clastic flows
- the ash would cover the Great Plains, halting grain production for the USA
- economic activity would be therefore affected and growing seasons worldwide could be stopped


Where does a hot spot occur?

- most are located well away from plate boundaries
- approximately 125 are thought to have been active over the past 10 million years