Gosses Bluff, about 205 km west of Alice Springs, in the Northern Territory, is one of the most significant impact structures in the world. This crater is thought to have been made by the impact of a large comet or meteorite, about 143 million years ago. It has been estimated that the original crater would have been about 22 km in diameter, and that the object which made the crater would have been travelling at 40 km/sec and released energy equivalent to 22 000 megatonnes of TNT. The original impact caused major disruption of the mainly Cambrian to Devonian sandstone and conglomerate strata, with a zone of intense disruption extending down to 4000 m. The intense pressure pushed up and jumbled the rock strata, as well as pulverising some of the rock. Although no extraterrestrial debris has been found in or around the crater, rock structures called 'shatter cones' are present. These are rocks with concentric cone-like fractures, and with sets of parallel grooves on their surfaces, produced by extreme shock. The structure we now see is the result of erosion - the crater would originally have had an outer raised rim, now removed by erosion, and a prominent central peak. The core of the original crater is now represented by a ring of low hills.
Copyright © Australian Museum, 2004