Caves are commonly formed by dissolution of soluble rocks by what agent?

• A. Mechanical fracturing due to ice wedging.
• B. Acidic water dissolving limestone.
• C. Biological weathering by roots alone.
• D. Deposition of silica in voids.

Answer: (B)

Caves form mainly through the dissolution of soluble rocks by acidic water. Rainwater and groundwater pick up carbon dioxide from the air and soil, creating a weak carbonic acid. This acid reacts with calcium carbonate in limestone, dissolving the rock and carrying the calcium and bicarbonate away. As water continues to flow through cracks and joints, it widens those openings into caverns. Over long timescales, the dissolved rock landscape becomes a network of caves, and later mineral-rich water can precipitate formations like stalactites and stalagmites from the dissolved minerals.

Other ideas don’t fit the dominant process: freezing-driven mechanical fracturing can crack rock but doesn’t dissolve it to form large voids; biological weathering by roots contributes only slowly and isn’t the primary cave-forming force; deposition of silica in voids would fill spaces rather than create them.