Ballroom Cave

The Ballroom Cave (and the nearby Stafford’s Cave) are spectacular structures with an interesting past.

The relatively modern caves have formed within Nile group limestone, which is between 24 and 34 million years old. These rocks were deposited in a shallow marine environment, when much of what is now modern-day New Zealand was subsided beneath the surface of the ocean. Over time, many layers of the marine organisms that inhabited the shallow waters and sea floor (bivalves, gastropods, bryozoans, brachiopods etc.) died, and their shells collected on the seabed. Together the remains of these organisms formed limestone, a rock made from the shells together with small amounts of sand.

The caves are considerably younger than the rocks in which they occur. They develop naturally as a result of chemical dissolution of the slightly alkaline limestone by slightly acidic rainwater and groundwater. As water runs over limestone, it accumulates in cracks and weaknesses in the rock and chemically weathers them, resulting in the breakdown and dissolution of the rock. Over many thousands of years, this process is enough to carve out river channels, sinkholes and – as in this case – cavernous underground caves.

These days the Ballroom Cave lies within a private farm and is managed by the Department of Conservation. The Ballroom Cave was once apparently the venue for a number of dances held between miners and the limited female population of the mining boom towns of Ferntown and Gibbstown. Have a little dance yourself – what do you think of the rumours?

Check out the stalactites which populate the roof of the cave and stretch toward the floor. These structures form when dissolved calcium carbonate (CaCO3) carried in water forms drips on the cave ceiling, and the CaCO3 precipitates out and accumulates before it has the chance to fall to the floor. They make a pretty unique disco ball!