Taiwan is an island of extremes: severe earthquakes and typhoons repeatedly strike the region and change the landscape, sometimes catastrophically.
Taiwan is an island of extremes: severe earthquakes and typhoons repeatedly strike the region and change the landscape, sometimes catastrophically. This makes Taiwan a fantastic laboratory for geosciences. Erosion processes, for example, occur up to a thousand times faster in the center of the island than in its far south. This difference in erosion rates influences the chemical weathering of rocks and yields insights into the carbon cycle of our planet on a scale of millions of years. A group of researchers led by Aaron Bufe and Niels Hovius of the German Research Center for Geosciences (GFZ) has now taken advantage of the different erosion rates and investigated how uplift and erosion of rocks determine the balance of carbon emissions and uptake. The surprising result: at high erosion rates, weathering processes release carbon dioxide; at low erosion rates, they sequester carbon from the atmosphere. The study will be published in Nature Geoscience.
Behind all this are tectonic and chemical processes. In rapidly growing mountains in particular, tectonic uplift and erosion constantly bring fresh rock material up from underground. There it is exposed to circulating acidic water which dissolves or alters the rock. Depending on the type of rock, this weathering has very different effects on Earth's climate. For example, if carbonic acid from the soil comes into contact with silicate minerals, limestone (calcium-carbonate or CaCO3) precipitates, in which the carbon is then bound for a very long time. In the case of a combination of sulfurous mineral, such as pyrite, and limestone, the opposite happens. The sulfuric acid that forms when pyrite comes into contact with water and oxygen dissolves carbonate minerals, thus producing CO2. This relationship between mountain building and chemical weathering is thought to affect our planet's climate on a scale of millions of years. But how exactly does the growth of the Alps or the Himalayas affect climate? Does silicate weathering accelerate, causing the climate to cool? Or does the dissolution of limestone by sulfuric acid dominate, driving the concentration of atmospheric CO2 up, with attendant global warming?
Read more at GFZ Geoforschungszentrum Potsdam, Helmholtz Centre
Image: Active bedrock seepage with yellow-brown weathering fluids; Lushan - Taiwan. (Credit: Kristen Cook (GFZ)