Weathering is a natural process, but human activities can speed it up.
For example, certain kinds of air pollution increase the rate of weathering.
Burning coal, natural gas, and petroleum releases chemicals such as nitrogen oxide and sulfur dioxide into the atmosphere.
When these chemicals combine with sunlight and moisture, they change into acids. They then fall back to Earth as acid rain.
Acid rain rapidly weathers limestone, marble, and other kinds of stone. The effects of acid rain can often be seen on gravestones, making names and other inscriptions impossible to read.
Acid rain has also damaged many historic buildings and monuments.
For example, at 71 meters (233 feet) tall, the Leshan Giant Buddha at Mount Emei, China is the world’s largest statue of the Buddha. It was carved 1,300 years ago and sat unharmed for centuries. An innovative drainage system mitigates the natural process of erosion. But in recent years, acid rain has turned the statue’s nose black and made some of its hair crumble and fall.