5 - Volcanism and Climate Change - Large Igneous Provinces

Question 1

What are Large Igneous Provinces?(Ernst et al., 2024)

Answer 1

On the Earth’s surface/at the bottom of the ocean, there are rock formations made of piles of lava with volumes of >100,000 km3(& frequently >1,000,000km3 - these are known as Large Igneous Provinces(LIPs)

Question 2

How long do LIP events last?(Ernst et al., 2024)

Answer 2

Typically either of short duration(<5 Myr, often <2 Myr) or consist of multiple short pulses over a maximum of a few tens of Myr

Question 3

What are the different types of LIPs?

Answer 3

Continental flood basalt(CFB), Ocean basin flood basalt(OBFB), Silicic

Question 4

Name some of the largest LIPs.

Answer 4

Siberian Traps(largest CFB & largest continental LIP), the Otong Java Plateau(OJP) and Kerguelen LIP

Question 5

Give some background information on the Siberian Traps.(Black et al., 2018)

Answer 5

They are 247-255 Ma, 7 million km2, 7-15million km3

Question 6

What are some of the characteristics of LIPs?

Answer 6

Mostly iron & magnesium-rich primitive lavas

Millions of cubic kilometres of lava(effusive) emplaced over 1-3 million years from a focus source

Dominant form of near-surface magmatism on other terrestial planets/moons of our solar system

Presumably generated by giant plumes in the mantle

Question 7

How are LIPs formed?

Answer 7

1. Rapid ascent rates of magma originating from Large Low-Shear-Velocity Provinces result in the large plume head(~ 2000km) rising through the mantle and spreading out to form a thermal dome
2. These form basaltic eruptions by decompression melting over an area up to 2000km in diameter
3. This can cause domal uplift of the crust of up to 1km in altitude
4. The unusually large melt fractions formed in the mantle cause the high extrusion rates that lead to LIP formation

Question 8

What are the suggested sources for these large quantites of magma found in LIP formation?

Answer 8

Adiabatic decompression melting

Hydration melting

Thermal anomalies in the mantle(higher temps than usual)

Question 9

What are some of the climatic and environmental impacts of LIPs?

Answer 9

Repeated effusive eruptions = enough CO2 to cause global warming

Repeated explosive emissions = enough SO2 to cause extended cooling

Activation of climatic feedback loops, ozone depletion from halogen emissions

Enhanced weathering of fresh volcanic rocks

Intensification of hydrological cycle

Silicate weathering

Halogen emissions

Question 10

What were the climatic impacts of the Siberian Traps LIP event(252 Ma)?(Black et al., 2018)

Answer 10

It caused swings in climate response, with cooling episodes being dispersed amongst a period of warming

The emissions themselves caused an initial warming of 8C, however, the consequent feedback loops resulted in a totla warming of 34C

Question 11

Describe the process of silicate weathering.

Answer 11

1. It is the process by which precipitation changes the composition of silicate rock through erosion
2. CO2 rises into the atmosphere due to hot basaltic lavas being degassed at the start of a LIP event
3. CO2 & H20 form carbonic acid from precipitation, eroding rocks that are then washed away in solution to bodies of water
4. This rock then eventually enters the mantle via subduction as it is located on the shelf of the oceanic plate
5. It is then melted in the mantle
6. It is then part of the rising magma which erupts through CO2 outgassing

Question 12

How do LIPs link to mass extinctions?(Stanley, 2016)

Answer 12

Long term Halogen emissions

Ozone depletion

Warming

Feedback loops

Ecological failure(e.g. Permian mass extinction when 96% of species disappeared)