The unmistakable shape of Gosse Bluff is seen on Missionary Plain, south of the Western MacDonnell Ranges in Central Australia. With improved road access this remarkable formation is now being included in travel plans of many visitors to Australia’s Red Centre.

Born from the massive impact of a comet (or low density asteroid) crashing into the earth’s surface some 140 million years ago, Gosse Bluff is not really a bluff at all, but crater walls; the relic of an awesome clash between an extra-terrestrial object and the Earth. With an estimated speed of around 40 kilometres per second, and crashing with an energy force in the order of 22,000 mega tonnes of TNT or one million times greater than the Hiroshima bomb, the effects of this impact would have been felt right around the world. The most recent scientific investigations carried out in the past 20 years conclude that the huge object was probably around 1 kilometre in diameter.

On the track

The lack of any space rock or other foreign debris in the area has led to the conclusion that this large comet had a low density consisting of an agglomerate of dust, ice and frozen carbon dioxide gases, which completely evaporated on impact - but not before penetrating around 500-600 metres underground and  shattering rock up to four kilometres below. The shock wave compressed a large area of rock in all directions and set off an immediate rebound forming a crater of around 20 kilometres in diameter. This rebound, from several kilometres down, forced huge sections of red hot, highly resistant sedimentary rock to the surface that now forms the Bluff as we see it today. During the blast some blocks of rock up to 100 metres long were hurled into the air and then fell back to the ground forming the outer crater rim around the impact core.

The massive detonation created a huge mushroom type of cloud that rose thousands of metres into the atmosphere. Back on earth there was utter devastation killing off all living matter for thousands of square kilometres around. Savage earthquakes, tidal waves, cyclonic winds and volcanic eruptions would have followed right around the world as it shook and trembled from one of the most cataclysmic events in the entire history of our planet. In the end, the globe settled back on its serene course in the solar system, but it was not the same planet. Vast changes in the genetic composition of plants and animals must have occurred and weather patterns would have been affected for many years.

Inside the Crater

Back at the impact site, weathering and erosion over millions of years have removed the outer rim, leaving only the highly resistant rocks which are seen today as the inner rim around the central crater; measuring overall around five kilometres in diameter and now largely filled with sand and sediment. When viewed from a distance a large 20-25 kilometre circular depression can be seen, in effect, Gosse’s outer crater. It is a spectacle that grips the mind and leaves most visitors wondering and just trying to imagine the scene when it happened millions of years ago. 

Aboriginal legend also records a dramatic background for this massive formation on the Earth’s surface. According to these  ancient beliefs, Tnorala (Father of the Mountains) was formed in the creation Dreamtime when a large group of women danced across the sky as the Milky Way. They were the stars taking the form of women. During this ceremonial dance of the ‘Milky Way women’, a mother placed her baby aside in a turna – a wooden baby carrier. The turna toppled over the edge of the dancing area high in the sky and, with a great force, the baby fell onto the ground and his turna fell hard on top of him; the force forming the circular walls of Tnorala. The infant was covered with sand and hidden from view. The mother as the ‘Evening Star’ and the father as the ‘Morning Star’ are, even now, still search for their missing earth bound child.

Crater rim

Millions of Years On

The silent sentinels of the crater walls seen today are now the solitary testimony of a truly dramatic past. Modern Australian history records that the mountainous crater was discovered in 1872 by Central Australian explorer Ernest Giles and named after his good friend, Harry Gosse, an officer at the then tiny outpost - Alice Springs Telegraph Station - and not the explorer, William Gosse, as is widely believed. When referred to as a bluff, Giles, from his vantage point on the ground, could not have imagined how it was formed and would not have seen the circular shape of this formation. This is possible today from aircraft and satellites which have helped to conclusively determine its origin.

Recent satellite images of the area show Gosse’s Bluff has a large halo effect around it - indicating the huge extent of the affected rock rebound around the central crater. It is estimated that the erosion, which has taken place over millions of years, has reduced the level of the crater walls and surrounding  countryside by nearly 2,000 metres from where they were immediately after the comet impact. Rings of differing vegetation are surface indicators of rearranged rock structures.

Information Shelter

Back in 1872 Giles mapped the eastern walls of the formation and, in search of water, he rode into the interior from the north-eastern side through a creek lined with gum trees. He found little water, so he left the area behind and continued along the MacDonnell Ranges where waterholes were far more reliable. He would have been blissfully unaware that he had just left a place which had witnessed such a significant event in the history of the world. It was not until the 1960s, in fact, that Gosse Bluff was identified as the site of a ‘bolide’ impact - a general term for a projectile from outer space which hits the Earth.

The entry to the circular pound, found by Giles, and into the centre of what is now known to be a crater, provides the only vehicular access to the inner area. Knowing the background of this cataclysmic act of nature millions of years ago, visitors are left with an eerie sensation driving through the winding access trail and then suddenly arriving into the open centre area where the wayward comet had struck with such unbelievable force. The interior, apart from a few small undulations, is generally quite flat, open and covered with spinifex, a few patches of scrub, and a handful of shapely white eucalypts. The rim walls rise up to around 200 metres above the floor of the crater and close examination reveals there are some sheer cliff sections with numerous rock overhangs and small caves.

Because of the area’s significance to Aboriginal people, and its existence as a recognised sacred site and ancient ceremonial ground, a good proportion of the crater floor has been closed off to visitors. The track leading to a parking and picnic area in the eastern crater floor  and a specially set up information shelter, together with a walking trail to a small hillside nearby, gives visitors an excellent vantage point from which to get a full 360° view of the inner crater area and to gain an overall feel for this incredible place.

The information display provides both scientific detail on the formation of the crater as well as Aboriginal legends and beliefs on its background.

With a number of old vehicle tracks on the pound floor now closed off, visitors are free to explore on foot the eastern section of the crater, but are asked not to enter the clearly marked areas of significance to local Aboriginal people. For those fit enough, the rim can be climbed in less than 30 minutes, and from there you can see some panoramic views over the pound, extending to the MacDonnell Ranges in the background. Although there are impact craters of similar or greater size to Gosse Bluff in other parts of the world, no others have such a large and spectacular inner crater enclosure.

The whole Gosse Bluff area (Tnorala), which was previously a scientific reserve, was handed to the Aboriginal Tnorala Association with freehold title on 18 April, 1991, in recognition of its significance to the Aboriginal people. It is now managed jointly by the Tnorala Association and the Conservation Commission of the Northern Territory. The area is open for daytime visits only and the lighting of fires or camping within the crater is prohibited.

Like many mountain ranges, cliffs and gorges, the crater walls of Gosse Bluff are particularly photogenic in the late afternoon or early morning when the sun’s rays reflect the warm colourful tones of the rock formations.

Yes, this is quite an awesome, eerie place. Spend a little time here when next in the Red Centre and try to imagine the horrific scene some 140 million years ago that created such a dramatic impression on our outback landscape.

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Written: Tue 01 Jan 2013
Printed: January, 2013
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