Hot spots- Content

Question 1

What are some examples of location of hot spots?

Answer 1

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

Question 2

What is the main theory of how hot spots form?

Answer 2

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

Question 3

How do volcanic island chains form?

Answer 3

• 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

Question 4

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

Answer 4

• 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

Question 5

How do supervolcanoes form?

Answer 5

• 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

Question 6

What are some general facts about Yellowstone supervolcano?

Answer 6

• 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

Question 7

Why is Yellowstone there?

Answer 7

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

Question 8

What are some possible warnings of another Yellowstone eruption?

Answer 8

• 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

Question 9

What would be the consequences of a Yellowstone eruption?

Answer 9

• 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

Question 10

Where does a hot spot occur?

Answer 10

• most are located well away from plate boundaries

- approximately 125 are thought to have been active over the past 10 million years