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Key Stage 2


The cave is limestone, a sedimentary rock, (chemical name CALCIUM CARBONATE). It is not soluble until it is attacked by rain water which is slightly acid. The limestone is then changed to CALCIUM BICARBONATE which is soluble. Then, it can be worn away. The features inside Dan-yr-Ogof are CALCITE, a mineral made during the dissolving of the rock. The most common features of caves are STALACTITES, STALAGMITES, FLOWSTONE, COLUMNS, SCALLOPS and CURTAINS. You will find examples of all these inside Dan-yr-Ogof.

FLOWSTONE is produced by sheets of calcite forming over sloping rock. Look out for the Frozen Waterfall.
COLUMNS occur when a stalactite meets a stalagmite and they join. Look out for the Alabaster Pillar.
CURTAINS are the result of water running across sloping rock, leaving minute layers of calcite behind. A good example of this can be seen in Cauldron Chamber.
SCALLOPS are the result of underground rivers shaping the walls and the floor of the cave into waves.


In 1912, Jeff and Ashwell Morgan entered Dan-yr-Ogof via a small passage, which can be seen just inside the cave. Their way into the cave was by coracle, across the small lake now known as the Coracle Pool.
Their lighting was from candles and oil lamps, and they plotted their route through the cave by marking the sand or mud with arrows.