'Climate And Microbial Activity Also Rapidly Eroding Himalayan Rocks', Finds Study
The study could prove useful in understanding the ecological stability and geological history of the Garhwal Himalayan region in future
Published : January 5, 2026 at 5:44 PM IST
Dehradun: The moisture-rich monsoon regions are eroding rocks three and a half times faster than the dry upper Himalayas and transporting nearly twice as many chemicals to rivers. This is directly related to the natural absorption of carbon dioxide, the supply of soluble minerals to river systems and the evolution of the Himalayan landscape. These facts have come to light in a study on weathering of granite rocks in the Garhwal Himalayas that was carried out by a team of scientists from the Indian Institute of Technology (IIT) Roorkee and Wadia Institute of Himalayan Geology.
The scientists found that Himalayan rocks are being rapidly broken down not only by geological pressure and temperature, but also by the climate and microbial activity. These processes not only affect the Earth's climate balance but also control the flow of nutrients in ecosystems.
According to the scientists, chemical weathering of rocks occurs more rapidly in warm and humid regions because water, temperature and biological reactions accelerate it. Meanwhile, tectonic activity breaks up rocks and provides new surfaces for chemical reactions.
Until now, weathering rates in the Himalayan region were estimated based on the chemical elements present in river water. This new study using the U-series isotope technique has revealed more precise information as this technique can determine when weathering began at a site and its speed.
The scientists compared Devguru Granite from the monsoon-affected Lesser Himalayas (the central and most extensive mountain range of the Himalayas, located between the Himadri and the Shivaliks) and Malari Granite from the humid Higher Himalayas. They also studied the role of microbial communities that break down minerals and enhance soil formation.
Due to the rapid geodynamic activities and high erosion rates in the Himalayan region, preserving ancient weathering profiles has been considered a major challenge. However, these geological studies have shown that preservation is possible in some parts of the Garhwal Himalayas.
"Erosion rates are not uniform across the Himalayas. While the fastest erosion rates are recorded in the transition zone between the Lesser and Higher Himalayas, the rates are much lower in the plains of the Lesser Himalayas and the dry, rain-shadow areas of the north," said Dr Pradeep Srivastava of IIT-Roorkee.
He added, "During the study, a unique geological site was discovered near Lawadi village in the Mandakini Valley, which holds significant promise for understanding the gradual weathering and soil formation of rocks formed millions of years ago. The site has been named the Lawadi Weathering Profile. This area is part of the ancient Ramgarh Group of rocks composed of approximately 1750-million-year-old porphyry granite."
Dr Srivastava explained that the rocks at the bottom of the slope are solid and lightly weathered, while those at the top appear to be turning into soil. The uppermost portion is rich in organic matter, where vegetation is thriving. However, no signs of soil erosion or sliding have been found in the lower portions.
However, the team of scientists collected 10 samples from the site for chemical and geochronological analysis. Three samples were also taken for microbial studies. He added that this study could prove useful in understanding the ecological stability and geological history of the region in the future.
The scientists have discovered a unique rock layer within the mountains of the Malari region of Chamoli district in Uttarakhand. This is known as Malari Weathering Profile. This layer developed on leucogranite rock formed millions of years ago.
The scientists believe this region is part of the upper layers of the Himalayas, known as the Higher Himalayan Crystalline. The rocks here, formed approximately 17 to 24 million years ago, contain rare minerals like tourmaline and muscovite. These rocks were found just below the Southern Tibetan Discontinuity (STDS) near the Tibetan border.
Studies on the Earth's layers have found that seasonal weathering of soil over time — the breakdown of rocks due to rain, temperature and moisture — is not uniform. Rather, the most significant changes are observed in the upper layers of the soil. They have found that significant changes in the mineral composition of soil up to 1.8 meters deep remained the same, while the layers approximately 2 meters below remained largely unchanged.
In the upper layers, the amounts of elements like calcium, sodium, and potassium are decreasing while those of elements like iron, titanium, and magnesium are increasing, meaning the soil is gradually becoming chemically mature.
Significantly, a soil sample found in the uppermost layer, named Malari Weathering Profile-10 differs from other profiles. It had a very high calcium content, indicating that this material was deposited from an external source rather than being indigenously formed. This difference suggests that the process of soil formation and change is not uniform everywhere.
The upper layers are directly affected by weather, while this process proceeds at a much slower pace in the lower layers. Therefore, weather also has an impact within the Earth, but it appears to be a little slower.
Dr Srivastava further disclosed that the scientists have found that rocks in two Garhwal regions of Lansdowne and Malari are gradually breaking and dissolving due to constantly changing weather and geological movements.
"Surface samples from the Lansdowne region revealed that the rocks are approximately 146,000 years old. The rocks in the Malari region show signs of weathering dating back approximately 60,000 years. Therefore, this change occurs very slowly. On average, approximately 50 to 60 millimeters of rock dissolves every thousand years. This rate is similar to that observed in other hot and humid regions of the world," he said.
The scientist also said that the Garhwal Himalayas are characterised by constant earth movement and uplift. This means that it is a tectonically active region. Consequently, in some areas, erosion is very rapid due to rain, snowfall and seismic activity.
In some areas, up to 5,000 millimeters of soil is lost every thousand years. In areas with less steep slopes, this rate is limited to only 60–80 millimeters. However, if the rate of erosion becomes too high, the old weathering record on the rock surface is quickly destroyed.
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