About 130 million years ago an eruption along the floors of the Great Southern and Indian Oceans produced enormous volcanic lava flows, which resulted in the formation of interlocking basalt columns.
Today the only view-able formations can be found on the beach at Bunbury (Back Beach), Capel and Black Point.
The columns were formed during a volcanic eruption, when the highly fluid molten basalt exploded through the sea bed and then began cooling rapidly. This resulted in horizonal contractions occuring in the lava, fracturing it in a similar way to how drying mud cracks. The cracks continued downwards into the lava as the mass cooled, forming pillar like structures. The size of the columns were determined by the speed in which the lava cooled.
The Bunbury Basalt Rocks are part of the Kerguelen large igneous province which formed as Australia, India and Antarctica split apart from each other about 130 million years ago.
Though they aren’t as spectacular as the hexagonal basalt formations at Giant’s Causeway in Northern Ireland, they are still worth a look. The basalt rock formations are located at Back Beach, Ocean Drive, Bunbury, Western Australia.