An effective climate change solution may lie in rocks beneath our feet

Why has Earth’s climate remained so stable over geological time? The answer just might rock you.

People have made the Earth worse, but now, we finally might have a solution for the problem we have caused, but will it work?

Official Report

By Benjamin Z. Houlton

July 16, 2020

Retrieved from https://theconversation.com/an-effective-climate-change-solution-may-lie-in-rocks-beneath-our-feet-142462

Rocks, particularly the types created by volcanic activity, play a critical role in keeping Earth’s long-term climate stable and cycling carbon dioxide between land, oceans and the atmosphere.

Scientists have known for decades that rock weathering – the chemical breakdown of minerals in mountains and soils – removes carbon dioxide from the atmosphere and transforms it into stable minerals on the planet’s surface and in ocean sediments. But because this process operates over millions of years, it is too weak to offset modern global warming from human activities.

Acid rain damage to buildings and monuments, like this sandstone statue in Dresden, Germany, is a form of chemical weathering.Slick/Wikipedia

Now, however, emerging science – including at the California Collaborative for Climate Change Solutions’ (C4) Working Lands Innovation Center – shows that it is possible to accelerate rock weathering rates. Enhanced rock weathering could both slow global warming and improve soil health, making it possible to grow crops more efficiently and bolster food security.

Acid rain damage to buildings and monuments, like this sandstone statue in Dresden, Germany, is a form of chemical weathering.

The Urey reaction runs at a higher rate when silicate-rich mountains such as the Himalayas expose fresh material to the atmosphere – for example, after a landslide – or when the climate becomes hotter and moister. Recent research demonstrates that humans can speed up the process substantially to help fight modern global warming.

Rock chemistry

Many processes weather rocks on Earth’s surface, influenced by chemistry, biology, climate and plate tectonics. The dominant form of chemical weathering occurs when carbon dioxide combines with water in the soil and the ocean to make carbonic acid.

About 95% of Earth’s crust and mantle – the thick layer between the planet’s crust and its core – is made of silicate minerals, which are compounds of silicon and oxygen. Silicates are the main ingredient in most igneous rocks, which form when volcanic material cools and hardens. Such rocks make up about 15% of Earth’s land surface.

When carbonic acid comes in contact with certain silicate minerals, it triggers a chemical process known as the Urey reaction. This reaction pulls gaseous carbon dioxide from the atmosphere and combines it with water and calcium or magnesium silicates, producing two bicarbonate ions. Once the carbon dioxide is trapped in these soil carbonates, or ultimately washed into the ocean, it no longer warms the climate.

When carbonic acid dissolves calcium and magnesium silicate minerals, they break down into dissolved compounds, some of which contain carbon. These materials can flow to the ocean, where marine organisms use them to build shells. Later the shells are buried in ocean sediments. Volcanic activity releases some carbon back to the atmosphere, but much of it stays buried in rock for millions of years.

Accelerated weathering

The biggest limit on weathering is the amount of silicate minerals exposed at any given time. Grinding up volcanic silicate rocks into a fine powder increases the surface area available for reactions. Further, adding this rock dust to the soil exposes it to plant roots and soil microbes. Both roots and microbes produce carbon dioxide as they decompose organic matter in the soil. In turn, this increases carbonic acid concentrations that accelerate weathering.

One recent study by British and Americans scientists suggests that adding finely crushed silicate rock, such as basalt, to all cropland soil in China, India, the U.S. and Brazil could trigger weathering that would remove more than 2 billion tons of carbon dioxide from the atmosphere each year. For comparison, the U.S. emitted about 5.3 billion tons of carbon dioxide in 2018.

Others: https://images.app.goo.gl/r1ztgVYFNtHyBLSx5

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