Gosses Bluff

Wolfe Creek Crater

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Australian Meteorites

A section of the Mundrabilla Meteorite at the South Australian Museum

Mundrabilla Meteorite: Three small masses assigned to what is referred to as the Mundrabilla meteor shower, were found in 1911 and 1918 on the Nullabor Plain near Mundrabilla.  In March 1966, two larger masses of about 8 and 11 tonnes were found by geologists R. Wison and A. Cooney and described under the name Mundrabilla; the larger mass of Mundrabilla is in Perth (Western Australian Museum), the smaller mass went to Adelaide Museum, then to Heidelberg for cutting and distribution. Since their discovery many more pieces have been found in the 100 km long strewn field, which is one of the largest in the world. In 1979, two more large masses weighing totalling about 1640 kilograms were found about 20 km east of the 1966 location. 
Mundrabilla has a very low iridium content and very high troilite content and is designated an anomalous iron.  The troilite is present in small nodules accounting for up to 35 % of the volume of the meteorite.  The "knuckle-shape"  of many individuals is a result of the selective ablation of troilite during atmospheric entry leaving knobby taenite crystals.

Henbury Craters: about 5,000 years ago a meteorite broke up as it entered the atmosphere over the Northern Territory. The Henbury Craters were formed at the impact. The largest (above) has a 180m diameter.

Molong Meteorite: discovered near Molong, New South Wales, during 1912. It was classified as a rare Pallasite meteorite which consists of olivine crystals surrounded by an iron/nickel matrix.

Cocklebiddy meteorite: found during 1949 in the Nullarbor Region of Western Australia. It was classified as an H5 Chondrite and this specimen is an end cut from the 19.5kg stone.

Gosses Bluff Impact Crater (NT)

Gosses Bluff is located west of Alice Springs and south of the Macdonnell Ranges, in the arid Missionary Plain in the Northern Territory. The bluff itself is a circular ring of hills 5km in diameter and 200m high, in the centre of a crater. It was formed 142 million years ago by the impact of an asteroid or comet up to 2km in diameter. The hills are part of the crater's central uplift, which formed when the earth's surface recoiled from the impact. A circular drainage system 24km in diameter marks the outer ring of the crater. The bluff is deeply significant to the Western Arrernte Aboriginal people, who own the Tnorala Conservation Reserve that contains the crater.
This impact is believed to have occurred at the very end of the Jurassic Period at a time when the largest dinosaurs, the sauropods, declined in number. This impact alone would not have been large enough to cause mass extinctions on a broad scale, but would certainly have caused a lot of local damage. The Morokweng crater in South Africa dates to roughly the same time period, although at 70km in diameter was a much larger impact than that which created Gosses Bluff.

Australia's other impact craters

It is estimated that each year the Earth receives about 100,000 tonnes of material from space. If this mass all arrived at once it would be a catastrophe! Most of it comes in meteor showers and is burned up by friction with air molecules in the upper atmosphere: a "shooting star" is a meteoroid either burning up or just grazing our atmosphere. These objects may approach Earth at speeds up to 70 km per second! The hundreds of impact craters on the earth's surface were caused by asteroids or comets colliding with our plant.
Around twenty four impact craters are known in Australia, ranging in size from less than 20m in diameter to perhaps more than 100km (see the World Crater Inventory). Some date back hundreds of millions (even billions) of years. Others are as recent as just a few thousand years old. Most probably did little more than localised damage. At least two Australian impacts may have contributed to mass extinctions.
There are several features geologists look for when identifying a geological structure as that of an ancient impact. Most craters are circular in shape, with an inner ring of raised rock known as an uplift. The central uplift structure forms when the underlying rocks rebound after the impact, throwing up a central mound or ring of rock. Surrounding the uplift will be a depression that is usually several times larger than the raised area. In time the outer ring may weather away, leaving only the central uplifted structure.
Other evidence for a large impact comes in the form of shocked quartz or breccia, or even veins of melted glass. These altered minerals form when sediments are heated and compressed by the impact, often to a greater degree than volcanism or earthquake activity could have produced. Occasionally elements that are rare on earth may occur in abundance in an asteroid or comet. The Chicxulub impact in Mexico, thought to be one of the causes of the extinction event that killed off non-avian dinosaurs, left an elemental calling card that can be found in many places around the world. The element known as iridium is rare here on earth (although does exist in the earths molten core), but can occur in higher concentrations in asteroids or comets. An iridium 'spike' occurs as a thin layer just above Late Cretaceous sediments all over the world, suggesting that a large impact threw up enough dust (containing iridium from the vaporised asteroid or comet) into the atmosphere for it to eventually settle almost everywhere. Of the two dozen or so impact structures known in Australia, these are the four largest.

Henbury Meteorite Craters, NT
These craters are located in the Northern Territory of Australia. The largest crater is approximately 180 metres in diameter. There are thirteen craters in total, believed to be around 5,000 years old that were first discovered in 1899. The first detailed survey of the crater area did not take place until 1937. More than 1200 kilograms of iron meteorite fragments have been collected from around the craters. More ...

Woodleigh Crater (WA)
The Woodleigh crater, mostly hidden beneath red sand, is located on Woodleigh Station, east of Shark Bay in Western Australia. The crater is up to 120km in diameter, and is recorded as the fourth largest impact crater on Earth's surface. Research suggests a bolide (asteroid or comet) 5km in diameter caused the crater. The impact structure is entirely underground. The central uplift structure 20km in diameter was first detected by drilling activities in the late 1970s, however its significance as an impact structure was only realised in 1997 during a gravity survey. In 1999 a core sample was taken. The thin veins of melted glass, breccia, and shocked quartz found would have formed under pressures 100,000 times greater than atmospheric pressure at sea level, or between 10 and 100 times greater than those generated by volcanic or earthquake activity. Only a large impact could have generated such conditions.
The Woodleigh impact, originally thought to be Late Triassic or Late Permian, most likely dates to around 364 MYA, corresponding to a minor extinction event in the Late Devonian Period when around 40% of species disappeared. Evidence for another impact in the Moroccan desert at around the same time suggests that more than one impact was involved in the extinction event.
More information

Wolfe Creek Meteorite Crater National Park (WA)
130km south of Halls Creek, Western Australia, is Wolfe Creek Meteorite Crater National Park, covering an area of 1 460 ha. Formed by a giant meteorite which crashed to earth thousands of years ago, the crater is 800 metres wide and 25 metres deep. The second largest meteorite crater in the world, access can be gained by an unsealed road off Highway 1. The road is generally passable from May to November but a check with the Halls Creek Shire Office for a road condition report is recommended throughout the year.
In southwest Tasmania, the Darwin meteorite impact crater contains small seams of glass produced by the collision of the meteor with local rocks.  Small pieces of Darwin glass in the form of flakes and tools has been identified in dated archaeological deposits up to 28,000 BP.  The distance of the sites from the Darwin crater, in terms of the actual routes humans would need to take in this terrain, varies from 25 to over 100km.

Veevers Crater

Veevers Crater (WA)
The Veevers Crater in Western Australia (Long. 22°58'S ~ Lat:125°22'E) is named after an Australian Geologist, Professor John Veevers. It was first discovered in 1975 and it is estimated to be around One million years old. The crater is one of only two impact craters where group IIAB meteorites have been discovered. The other is the Sikhote-Alin crater group in Russia. It is approximately 70 metres in diameter and approximately 1 kilogram of fragments have been recovered. 

Dalgaranga Crater (WA)
The red earth of Dalgaranga Station 75 kilometres west of Mount Magnet in Western Australia is scarred by the impact of a huge meteorite which, not that long ago, slammed a crater into the ground. The crater, the smallest in Australia with a diameter of just 21 metres, was discovered by an Aboriginal stockman, Billy Seward in 1921 when he almost rode full-tilt into it during mustering. He showed it to station manager Gerard Wellard, who recognized it for what it was.
Realizing the crater's scientific importance, he gathered up enough fragments of the meteorite to fill a gallon tin (about 4.5 litres) and sent them to the WA Museum. Unfortunately, the Museum and the Mines Department shared the same building at that stage, and the samples were misplaced. By the time Wellard showed up in Perth almost a year later, the Mines Department was no longer in the same building as the Museum and nobody knew where the fragments were. One of the fragments was found years later among the dust and red tape and a report analysing this piece was released in 1938. Unfortunately, the report contained a few mistakes, the chief error being that the crater was first reported by a Mr Wellard, not Wellard. This caused a major problem in years to come. It was only resolved by the most extraordinary coincidence. Scientific interest in the Dalgaranga Crater grew after the publication of a scientific paper in 1960. More ...