A slow-motion chemical reaction
In the Nurata Mountains of Uzbekistan, a vast and quiet geological process is actively removing carbon dioxide from the atmosphere. The main rock is serpentinite, a greenish, waxy-looking metamorphic rock that makes up large parts of the range. This rock is the product of a deep-Earth process called serpentinization, where ultramafic rocks from the Earth's mantle, rich in minerals like olivine and pyroxene, are altered by water.
When this serpentinite is exposed at the surface to rain and air, it weathers. This isn't just a simple physical breakdown; it's a chemical reaction. The magnesium-rich silicate minerals in the serpentinite react with carbonic acid—which forms naturally when atmospheric CO2 dissolves in rainwater. This process breaks down the serpentinite and re-locks the carbon into new, stable carbonate minerals like magnesite (MgCO3). The mountains are slowly turning atmospheric gas into solid rock, sequestering the carbon for geological timescales. This natural form of carbon capture is studied for scientists looking for ways to mitigate climate change.
A suture of an ancient ocean
The Nurata range is a western extension of the great Tian Shan mountain system. Its geology records continental collision. These mountains form part of a suture zone, the remains of the Turkestan Ocean, which closed when the Kazakh-Kyrgyz continent collided with the Alai microcontinent during the Paleozoic era. The ultramafic rocks that eventually became the Nurata serpentinites are part of an ophiolite, a slab of ancient oceanic crust and upper mantle that was thrust onto the continental plate during this collision.
The scale of carbon sequestration here is significant. Studies focusing on similar ophiolites, like one in Oman, estimate that natural carbonation can lock away 10,000 to 100,000 tons of CO2 per year. The "100,000 cars" figure for the Nurata range comes from applying these principles through mass-balance calculations, which measure the chemical inputs and outputs of the weathering system. While this natural process is powerful, it is also very slow. Researchers are investigating ways to accelerate this mineral carbonation, often by crushing serpentinite to dramatically increase the reactive surface area, as a potential engineered climate solution.