5 - Volcanism and Climate Change - Large Igneous Provinces Flashcards
What are Large Igneous Provinces?
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 - these are known as Large Igneous Provinces(LIPs)
What are the different types of LIPs?
Continental flood basalt(CFB), Ocean basin flood basalt(OBFB), Silicic
Name some of the largest LIPs.
Siberian Traps(largest CFB & largest continental LIP), the Otong Java Plateau(OJP) and Kerguelen LIP
Give some background information on the Siberian Traps.
They are 247-255 Ma, 7 million km2, 7-15million km3
What are some of the characteristics of LIPs?
Mostly iron & magnesium-rich primitive lavas, millions of cubic kilometres of lava(effusiveemplaced 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
How are LIPs formed?
Rapid ascent rates of magma originating from Large Low-Shear-Velocity Provinces result in the large plume head rising through the mantle and spreading out to form a thermal dome to form basaltic eruptions by decompression melting over an area up to 2000km in diameter → this can cause domal uplift of the crust of up to 1km in altitude → the unusually large melt fractions formed in the mantle cause the high extrusion rates that lead to LIP formation
What are the suggested sources for these large quantites of magma found in LIP formation?
Adiabatic decompression melting, hydration melting, thermal anomalies in the mantle(higher temps than usual)
What are some of the climatic and environmental impacts of LIPs?
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
Describe the process of silicate weathering.
It is the process by which precipitation changes the composition of silicate rock through erosion; CO2 rises into the atmosphere due to hot basaltic lavas being degassed at the start of a LIP event →CO2 & H20 form carbonic acid from precipitation, eroding rocks that are then washed away in solution to bodies of water → this rock then eventually enters the mantle via subduction as it is located on the shelf of the oceanic plate → it is then melted in the mantle → it is then part of the rising magma which erupts through CO2 outgassing
How do LIPs link to mass extinctions?
Long term Halogen emissions → ozone depletion → warming → feedback loops → ecological failure(e.g. Permian mass extinction when 96% of species disappeared)
