Recently, I visited the South Coast to see some friends and Roy decided he would like to tag along - after all there were a number of things he had wanted to see in the area and this was a perfect opportunity to make a start. We had a great break and the weather even cleared up beautifully while we were away! Since then the weather has turned nasty again, so Roy decided he would like to bring a little sun back through his post and the perfect place to take you was Kiama (NSW) and it's blowholes - the sun was just beautiful glinting off the spray!
Kiama has two blowholes, the well known large one, sometimes touted as the largest in the world, and another known as 'The Little Blowhole'. The main blowhole is located on Blowhole Point Headland in Kiama and is accessible by Blowhole Point Road. It is not far from the visitors centre and walking distance to the town centre, railway and cafes. It was this blowhole which was discovered by Bass on December 6, 1797. He had anchored his boat in the calm bay which later became Kiama Harbour and saw the main blowhole while he was there. The Little Blowhole is about 2 kilometres, as the crow flies, away from the main blowhole and is located off Tingira Cresent. Although the main blowhole is fully enclosed by safety fences, the little blowhole is easily accessible so I recommend adults supervise children when visiting.
The blowholes, particularly the main, large one, are very important to Kiama. In fact, the name Kiama is taken from the Aboriginal word for the area, kiarama, which means 'where the sea makes noise'. This probably refers to the blowhole which makes a very identifiable, loud 'whoosh' as it explodes. Both blowholes are spectacular in their own way. The Little Blowhole does not tend to erupt as massively, being much smaller, but is more consistent in its activity. The main blowhole, on a good day is extraordinary, blowing water metres into the air, even so high that it washes cars in the upper car park! On a calm day though, the main blowhole is unlikely to put on a show, making the Little Blowhole a much better bet.
So, how do blowholes form and how do they work? Kiama itself sits on top of two major lava flows and these formed into a very hard rock. Where the blowhole sits there was a dyke in the rock, or a channel of softer rock (at Kiama this was a columnular basalt). Over time the sea eroded the softer rock faster than the rock surrounding it, creating a sea cave through the rest of the rock. Then, part of the roof of the cave, made of the harder rock, collapsed into the cave below, leaving the void we see as the blowhole. There is a chamber beyond the hole through which the water erupts though and when the waves enter the channel, air is compressed into this chamber under high pressure. When the water wants to retreat again, the entrance to the tunnel is blocked by the wave. The air compressed in the chamber behind also wants to escape and forces the water in the channel up through the hole. The air which is also escaping makes the oomph noise which accompanies the explosion of water. Even on a calm day, you will hear the oomph of the air escaping! If you would like to read more about the Kiama blowholes click here.