Spectacular geology: The Barron Gorge and beyond

Skyrail Nature Diary: May 2011

Visitors from all around the world flock to Tropical North Queensland for its geologically spectacular beauty. The history and formation of the destination is equally as fascinating and intriguing.

The entire region of Cairns was once under water and supported a large coral reef system. It was dominated by calcareous sponges and unusual types of coral, now long extinct, and was bisected by a fault line that ran along the length of the area.

One day the two continental plates that were butting against each other collided. The upheaval created a new mountain chain known as the Hodgkinson Formation and is claimed to have rivalled the Himalayas in its height. Estimates indicate that the highest peaks reached 11km.

The coral reefs of the Cairns area were severely crushed during the mountain building process, only leaving chalk in its wake. In the Chillagoe area, the reef structures survived the uplifting and were turned into limestone caves. This type of landscape is now known as karst.

Some time later, the mountain chain experienced volcanic activity along the old fault line. The result was the creation of underground, granite, volcanic plugs. In time, the mountains eroded and the granite was exposed, leaving behind a series of granite tors - Red Peak is a good example of this (you can see Red Peak via Skyrail Rainforest Cableway on the journey to Red Peak Station).

The eroded mountain mostly ended up in central Australia, filling up the original inland sea and creating a plateau about 300 metres above sea level. It's worth noting that Queensland was originally pointing south. This means that the eastern Australian coastline has rotated about 90 degrees northwest. The fault line now runs through Indonesia and the Philippines.

Interestingly during the Ice Age years after, the continental shelf was dry land. This means that all signs of early human settlement in coastal Queensland were buried under water and the Great Barrier Reef, due to the large icecaps melting. The is often referred to as the 'Great Flood', however some scientists disagree with this scenario.

Barron Gorge - Barron Gorge National Park

Normal geological processes formed the Barron Gorge, which meanders through the Barron Gorge National Park. The Barron River, which starts near the Hypipamee Crater just south of Atherton, flows first east through Mareeba, before continuing south through Kuranda. The rocks of the gorge are for the most part, of sedimentary origin, which means they are soft and crumbly. This meant that when the Barron River flowed through the area over a lengthy period, it slowly gouged out the gorge.

The formation of the Barron Falls, however, was an unusual process. Most waterfalls form by having the river flow over the edge of a gorge or a valley. Barron Falls is located far away from any such area, being closer to the middle of the gorge.

Geologists believe that just behind Barron Falls, Barron River was joined by the Mitchell and Clohesy Rivers. This created a more powerful flow in front of the point where they joined and therefore gouged out more of the gorge at that location, rather than behind it. There are only about three waterfalls in the world that were created in this fashion!