Mr K. McEachern and Mr J. Hutchesson and his sons Alan & Bernie, first explored the cave in 1936.The original entrance was a 17m vertical shaft, as visitor access was restricted a stairwell had to be dug through the limestone, this stairwell took Keith and Bunny 5 years to dig. They developed the cave as a tourist attraction with “Bunny" Hutchesson acting as the first permanent guide, conducting tours from 4th January 1941. Since 1980, the cave has been part of the Lower Glenelg National Park.
Most limestone caves are formed by water seeping down through cracks and fault lines in the limestone, dissolving the rock and creating fissures and tunnels. The formation of Princess Margaret Rose Cave, however, was assisted by water from the Glenelg River which worked its way along a fault line for approx 500m. This occurred above its present height. The water scalloped the walls of the cave and wore a reasonably level floor.
Rainwater, as it seeps from the surface, acts as a weak acid to dissolve the limestone, producing a solution of calcium bicarbonate. When this reaches the air of the cave, carbon dioxide is released and calcium carbonate is deposited in the form of calcite crystals. These crystals make up the diverse and spectacular formations of the cave. The different colours are caused by tannins and minerals washed down by rainwater from overlying soil.
As the solution drips from the cave roof, deposited carbonate is left adhering and a stalactite is formed. Straws or tubular stalactites are long, thin hollow stalactites with a solution flowing down inside the centre.
Solution dripping from a stalactite builds a stalagmite from the cave floor. If a stalactite and stalagmite join they form a column and if that thickens it becomes a pillar. Flow stone formations are caused by water flowing over the walls leaving a smooth surface. Other formations at the roof line are shawls, blankets and bacons. The shapes and colours of these narrow formations are accurately described by their names.
Perhaps the most unusual formations in the cave are the helictites.
Defying gravity, these long, thin formations grow in all different directions. No one is certain how they form, but the commonly accepted theory is that they begin on crystals and are shaped by surface tensions and capillary action.
Other mysterious formations in the Princess Margaret Rose Cave is the rarely seen cave coral, rimstone pools and sawtoothed shawls.