Eruption at hotspots and Large Igneous Provinces

What is a flood basalt?

A massive outpouring of basalt that commonly erupt intermittently over a long period of time (1-3 million years). It covers areas of 2000-2500km across. These form many layers of rock which have built up over time by many volcanic eruptions.

What does a mantle plume produce?

Magma which has low viscosity, and so it floods as it quickly travels and covers the landscape with flat plateau.

How thick are mantle plumes?

2km thick, with many individual lava flows exceeding 10km3

Where can mantle plums form?

They can be formed on land: continental flood basalts or the oceanic plateaus. Found in Colombia, Siberia (biggest) and India.

How are mantle plumes formed?

• Mantle plumes are very hot but solid material that rises from the junction between the mantle and the liquid outer core, the same process that makes convection currents in the mantle.

• The material making up the plume is mafic (dark in colour, igneous rock rich in magnesium and iron) but changes chemically by the time that it reaches the surface depending on whether the last leg of the plume’s route to the surface is through oceanic or continental crust.

What are the risks to life due to LIP?

• They are rare events. There hasn’t been a flood basalt in 16 million years, which formed the Colombia river basalt province - little threat to human life.

• However, gases released by the eruption may have change the global climate and scientists have found that these events have led to 4 out of the 5 mass extinctions on Earth.

What are the climate impacts of LIP?

• LIPs are earth shattering events. Millions of cubic kms of magma pounds up below the lithosphere, before breaking through the lithosphere and crust erupting over several millions of years.

• There’s a strong correlation between the creation of LIPs and Earth’s climate history, given the volume of material produced that’s hardly surprising.

• Short-term impact: global cooling but as CO2 is the most significant gas emitted by effusive explosions

• The long term impacts would be global warming and ocean acidification.

Define Hot spots

This is a fixed area of intense volcanic activity where magma from a rising mantle plume reaches the Earth’s surface.

Explain the link between hot spots and volcanic eruptions

As the Pacific plate has slowly moved north west over the Hawaiian hotspots (10cm/year), vast amounts of basalt have accumulated on the ocean floor to produce the Hawaiian islands.

What has happened to the East African Rift Valley over the last 30 million years?

The crust has been uplifted and stretched, causing tension within the locals rocks. The result is rifting, with magma forcing its way to the surface and creating a line of active volcanoes (E.g: Kilimanjaro).

Define super volcanoes

A volcano that erupts more than 1000km3 of material in a single eruption event

What is found at Yellowstone, Wyoming?

A caldera which is an enormous crater in the western central position of Yellowstone National Park.

How was the Yellowstone crater formed?

It was formed by a cataclysmic (large scale) volcanic eruption about 640,000 years ago. Its 50 by 70 km.

What was the magnitude of the Yellowstone eruption?

VEI of 8

Define a caldera

A large cauldron - like a hallow that forms shortly after the emptying of a magma chamber in a volcanic eruption.

What are the three main features of the Yellowstone caldera?

• Yellowstone Lake

• The Western Thumb

• Two magma domes

What was the style of the eruption that caused the creation of the Yellowstone caldera?

• 2.1 million years ago

• It coated 5,790 square miles with ash - Total material ejected - 6000x of Mt St. Helen

• Heat from the mantle plume has melted rocks in the crust, creating two magma chambers of partially molten, particularly solid rock near Yellowstone’s surface. This has caused the crust to expand and rise - causes stress on the overlying crust eventually forming faults that the magma fills. This causes pressure causing a large eruption.

Who monitors the Yellowstone volcano?

• The Yellowstone Volcanic Observatory was established in 2021

• They monitor the volcano regularly with a large network of seismic stations and technology. They collect information on temperature, chemistry and gas concentrations

• It is unlikely that Yellowstone’s volcano will erupt in the next few hundreds years.

If Yellowstone erupted what would the impact be on humans?

• It would spread deadly ash killing vegetation and humans

• Risk of hydrothermal explosion occurs every two years at Yellowstone reduced risk as its very rare.

• Damage from large earthquakes - Many earthquakes but low magnitude.

• Lava flows - however we’re in the dormant stage