Blowhole history
The main Kiama Blow Hole was discovered by George Bass on his voyage of coastal exploration on December 6, 1797, after anchoring his whaleboat in the sheltered bay which became Kiama Harbour.
The shore Bass wrote, showed evidence of considerable volcanic fire and on the point he found: "The earth for a considerable distance round in the form approaching a circle seemed to have given way; it was now a green slope.....Towards the centre was a deep ragged hole of about 25 to 30 feet in diameter and on one side of it the sea washed in through a subterraneous passage...with a most tremendous noise..."
Bass was not, in fact, the first to discover the Kiama Blow Hole, as local Aboriginals had for generations referred to it as Khanterintee.
In January 1889 a performer by the name of Charles Jackson attracted large crowds to see his crossings of the mouth of the Blow Hole on a tightrope.
A smaller "little Blow Hole" is located a few minutes south of the main Blow Hole & performs best under moderate seas.
Little
Blow Hole in action
How Blowholes work
Under the right conditions, large waves enter the mouth of the Blowhole & compress the air within the inner cavity.
As the retreating water leaves, it is forced upward by the compressed air, as the mouth is still blocked by the receding wave.
The escaping air causes the loud "oomph", which accompanies the water spout.
Over many years the Blowhole will become less vigorous, as the underground cavity erodes due to the pounding waves.