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HomeScienceWarm and humid climate make rocks more brittle, accelerate weathering, study finds

Warm and humid climate make rocks more brittle, accelerate weathering, study finds

New study by University of North Carolina confirms that increased humidity in air and rising temperatures leads to rocks weathering faster.

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Bengaluru: Warm and humid weather plays a major role in accelerating the weathering process of rocks, breaking them down faster, a new study has found.

Weathering is the natural process of breakdown of rocks into smaller pieces and minerals. The slow phenomenon is an ongoing process over millions of years, leading to formation of soil and sand. The process also releases carbon.

The study by researchers at the University of North Carolina, US, published in the Geophysical Research Letters journal in December, was undertaken by “listening” to acoustic emissions from naturally cracking rock over many years.

The research team attached numerous sensors to multiple rocks to listen for signs of cracking internally. These sensors recorded seismic activity or vibrations, and collected weather data including temperatures and humidity.

Understanding the impact of a warming world on weathering of rocks is important as rocks play a crucial role in trapping carbon for millions of years. This is a part of the carbon cycle on earth, where carbon takes about 100 to 200 million years to move between rocks, soil, water and atmosphere.


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Subcritical cracking of rocks accelerated by worsening climate changes

Weathering is of two kinds — mechanical weathering, where a rock is merely broken into smaller pieces without changing its composition, and chemical weathering where something like acid rain reacts with the rock to lead to a chemical process that can crack it.

The study aimed to quantify how mechanical weathering rates corresponded with increase in pressure, temperatures, and relative humidity as a proxy for global climate change.

After listening to years worth of natural cracking sound data, the researchers found that higher temperatures and humid air corresponded to higher rates of fractures in the rocks, contributing to increased weathering.

A key process in weathering is ‘subcritical cracking’ or the very slow process that leads to development of a steady crack internally.

Martha Cary Eppes, a geomorphologist at the University of North Carolina at Charlotte and lead author of the new research compares subcritical cracking to the slow growth of a crack on a car windshield, as compared to the instantaneous crack if the windshield is struck with a hammer.

“The crack grows slowly and steadily, with very low forces being applied to that crack,” she said.

The study was able to confirm that subcritical cracking was exacerbated by the worsening climactic conditions too. Additionally, these cracks drive chemical reactions in the rock, which render the areas surrounding these cracks weaker than the rest of the structure, making it more susceptible to further cracking.

The study also confirmed that the biggest driver of cracking was increased water vapour, followed by increased temperature.

The findings have implications because not only are global temperatures climbing, high temperatures are also leading to more evaporation. Warmer air can hold more moisture, which increases humidity and contributes to rock degradation, followed by carbon release.


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