Caves begin to form when rainwater seeps into soil where it absorbs a small amount of carbon dioxide. Water mixed with carbon dioxide forms a weak carbonic acid solution that is able to dissolve rock (particularly dolomite or limestone). Water flow creates and enlarges underground passages, until finally the water surfaces at a spring. As the flow of water continues to erode deeper into the surface, the openings left behind become caves.

The limestone and dolomite bedrock of the Ozarks´ mountains, where Marvel Cave is located, contains the mineral calcite. Rainwater dissolves carbon dioxide found in the soil and air to form a weak acid solution called carbonic acid. As with the cave atmosphere, carbon dioxide is released from the solution, which causes small deposits of crystallized calcite. This crystallized calcite forms stalactites. Growth rates of stalactites can vary greatly but the average is one inch per 25 to 100 years. As this process is driven by rainwater, increased rainwater will increase the rate at which stalactites form.