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Large igneous province

earth science Maturity 9-11 Next article →

A Large Igneous Province, or LIP, is an enormous accumulation of igneous rocks. These massive geological features are much larger than typical volcanic systems. They form when huge amounts of magma move through the Earth's crust toward the surface. This process creates both intrusive rocks, which form underground, and extrusive rocks, which erupt onto the surface.

Flood Basalt Map
Flood Basalt Map

Common intrusive forms include sills and dikes.

The difference between a sill and a dike
The difference between a sill and a dike

LIPs are fundamentally different from the volcanoes we see in everyday life. They represent massive crustal emplacements of rock that happen through unique geological processes.

The mechanism behind a LIP involves a very rapid and intense movement of magma. Most of the rock in a basaltic LIP is emplaced in less than 1 million years. This rate of effusion is much higher than the magma movement seen at mid-ocean ridges. One major theory is that mantle plumes cause this activity. A mantle plume is a rising column of hot material from deep within the Earth. As the plume rises, it can spread out radially beneath a tectonic plate. This spreading can cause the surface above to lift or bulge upward.

mantleplume
mantleplume

Another theory suggests that plate-related stresses cause ruptures in the lithosphere. These fractures allow melt to reach the surface from shallower sources in the mantle.

Scientists categorize LIPs based on their chemical makeup and how they form. Most LIPs are dominantly mafic, meaning they are rich in magnesium and iron. However, some contain significant amounts of other materials. For example, the Columbia River Basalt Group in the United States contains large volumes of rhyolite. This rhyolite is very dry and has eruption temperatures between 850 °C and 1000 °C. Other classifications include large granitic provinces, such as those found in the Andes Mountains. There are also large volcanic provinces (LVP) and large plutonic provinces (LPP). These terms help geologists discuss the specific types of rock and structures present.

The study of these provinces has evolved through careful scientific definition. In 1992, researchers Coffin and Eldholm first defined the term. They described LIPs as massive mafic provinces covering more than 100,000 km². They noted these provinces were distinct from normal seafloor spreading. In 2008, Bryan and Ernst refined this definition to be more specific. They focused on the timing and volume of the magma. They noted that a LIP should have a lifespan of about 50 million years. Most importantly, they observed that over 75% of the total volume is often emplaced during short pulses of 1 to 5 million years. This helped distinguish LIPs from smaller features like seamounts.

The scale of these provinces is truly massive. A LIP can cover an area of several million square kilometers. They can also reach volumes of approximately 1 million cubic kilometers. While the old definition required 100,000 km², the modern threshold has been lowered to 50,000 km². Some LIPs remain geographically intact, like the Deccan Traps in India. Others have been broken apart by the movement of tectonic plates. For instance, the Central Atlantic magmatic province is now split between Brazil, North America, and Africa.

Flood Basalt Map
Flood Basalt Map

LIPs are also important because of the valuable resources they contain. They are often associated with economic concentrations of metals. Many LIPs contain copper, nickel, and iron. Some are linked to major mineral provinces that hold platinum group elements. In silicic LIPs, scientists find deposits of silver and gold. They can also contain titanium and vanadium. Beyond metals, some LIPs are associated with trapped hydrocarbons, such as oil and gas. This makes the study of these provinces very important for the economy.

Finally, LIPs are deeply connected to the history of Earth's environment. The formation of these provinces can cause major changes in the atmosphere and the oceans. The rapid release of greenhouse gases from the lithosphere can lead to significant climate shifts. Some researchers, like Michael Rampino and Richard Stothers, have identified 11 distinct flood basalt episodes in the last 250 million years. These episodes coincided with mass extinctions of species.

Large Igneous Provinces and Bolide Impacts
Large Igneous Provinces and Bolide Impacts

By studying how LIPs triggered these past changes, scientists hope to better understand current and future environmental shifts on our planet.

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🖼️ Images & Media (5)
File:Flood_Basalt_Map.jpg
Flood_Basalt_Map.jpg
File:3-Devils-grade-Moses-Coulee-Cattle-Feed-Lot-PB110016.JPG
3-Devils-grade-Moses-Coulee-Cattle-Feed-Lo...
File:Large Igneous Provinces and Bolide Impacts.png
Large Igneous Provinces and Bolide Impacts.png
File:The difference between a sill and a dike.jpg
The difference between a sill and a dike.jpg
File:mantleplume.png
mantleplume.png
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