Acid rain causes erosion by chemically reacting with certain minerals in rock, causing it to dissolve in the water and otherwise escape the structures in which it is bonded. This is a particularly a problem with limestone and rocks derived from it, such as marble. The basic constituent of limestone is calcium carbonate, which is very vulnerable to acidic compounds.
Acid rain is created when industrial and other modern processes release sulfur compounds into the atmosphere. These react with water, creating sulfuric acid, the major active constituent of acid rain. This dissolved acid is carried with rain onto limestone or marble, and the calcium carbonate in the rock reacts with it. This reaction generates water, carbon dioxide, calcium ions and sulfate ions. All these products are then carried away with the flowing rainwater. This both erodes natural and man-made structures made of limestone, and depletes soil of important calcium compounds.
Acid rain also harms the environment in other ways. Acid rain accumulates in bodies of water, such as lakes, making them more acidic. This can make lakes so acidic they no longer support most fish and other types of organisms. In addition, the dissolution of calcium and other compounds in soil can release toxic aluminum and other ions into the environment.