Gosses Bluff Crater
Credit: NASA public domain photo.

Gosses Bluff Crater is near the exact middle of the Australian continent.[1]

Australia has at least 26 impact craters

Asteroid impact craters on Earth are much fewer in number than those on the moon. This isn't because the moon is an asteroid magnet, but because Earth’s weather and tectonic processes make these craters disappear over time.[2] Also, our planet’s surface is 71% water,[3] so chances are that an asteroid would land in the oceans somewhere more frequently than land.

On Earth there are at least 170 known impact craters which have been identified,[2] and they are best preserved in areas with hard rocky surfaces, or dry sandy deserts where erosion (such as due to rain) is minimized.[4]

Therefore one of the best places in the world where some excellent impact craters have been preserved, in some cases for tens of millions of years, is the dry interior of the continent of Australia. Significant portions of Australia have a hard rocky geological shield in addition to the dryness.[5]

Of the known impact craters in Australia, of which there are 26 and possibly more,[6] two are often said to be the very best, and they are discussed below.

Western Australia's Wolfe Creek Crater

Wolfe Creek Crater
Credit: Wikimedia Commons photo by Happy Little Nomad, CC BY-SA 2.0.

Wolfe Creek Crater's appearance after some rain. This crater is one of the youngest large impact craters known on our planet.[7]

This impact crater is 150 km (93 miles) south of the town of Halls Creek in Western Australia. This town is the only one its size (about 1,200 residents) for a great distance along the Great Northern Highway (National Highway 1).[7]

To the northeast, the town of Kununurra, with about 3,750 residents, is 360 km (224 miles) away. To the west, the town of Derby, with just over 3,000 residents, sits 50 km (30 miles) north of the highway and 547 km (340 miles) from Halls Creek.[7]

Areas like this (the Kimberley Region of Western Australia), and Australia’s vast deserts that cover most of the interior of the continent, are the reason that Australia has about 95% the area of the continental 48 states of the United States of America, yet only about 7.5% the population (23 million versus 306 million).[8][9]

The Wolfe Creek Crater is estimated to be only about 300,000 years old.[7] Back then the continent hosted some animals that are now extinct, including the marsupial lion, the giant diprotodon, a 15-foot (4.5-meter) monitor lizard named megalania, and some enormous flightless birds.[10] Also, Australia was connected to New Guinea by a land bridge.[11]

The crater is now a little over half a mile (about 875 meters) in diameter, and the crater floor sits about 200 feet (60 meters) from the rim. The rim stands about 80 feet (25 meters) above the surrounding barren desert.[7]

The actual asteroid is thought to have been traveling over 30,000 miles per hour (54,000 kilometers per hour) when it hit, and is said to have likely weighed 50,000 tonnes (55,000 tons), and it would have been around 90 feet (27 meters) in diameter if it were spherical.[7]

The site of the crater is Wolfe Creek Meteorite Crater National Park, and it sits within Australia’s Great Sandy Desert.[7] This crater is generally considered one of the top few best impact craters on Earth, possibly trailing only Meteor Crater in Arizona, and Amguid Crater in Algeria. A subjective assessment, although this is what I’ve seen many websites suggest, and I'd have to agree.[7]

Northern Territory's Gosses Bluff Crater

Gosses Bluff Side View
Credit: Public domain photo.

This is a view of Gosses Bluff Crater from about 30 km (19 miles) away to the north. It stands over 150 meters (500 ft) above the surrounding desert terrain.[1]

This impact crater is considerably older than Wolfe Creek Crater discussed above, estimated at 142 million years old, putting it in the first few million years of the Cretaceous Period. For its age, this crater is in very good shape. As can be seen in the photo, it easily stands out against the surrounding area, clearly recognizable as an impact crater.[1]

Back when this asteroid struck Australia, the continent was joined to Antarctica, New Zealand, and South America, forming the last remnant of the great southern continent of Gondwana.[12] Australia was cooler and wetter then, and located further south. About a third of the interior was a shallow sea called the Eromanga Sea.[13] It’s likely that no mammals yet existed on the continent, although there were certainly dinosaurs and probably some of the earliest birds.

The crater was originally about 13.5 miles (22 km) in diameter, and after many millions of years of erosion, the present day crater is about 3.1 miles (5 km) in diameter, and stands over 500 feet (150 meters) above the surrounding desert. This crater was caused by a very large asteroid, estimated at 1 km (0.6 miles or 3,200 feet) in diameter.[1]

The location of the crater is near the center of the Australian continent, about 109 miles (175 km) west of the town of Alice Springs (population 25,000). The closest town that is near this size is Mount Isa in Queensland, just over 700 miles (1,100 km) away, with 22,000 residents.[1]

As you can see by the locations of these craters, Australia's population is very sparse in the arid interior, being confined mostly to the coasts, especially the East Coast where the largest cities of Sydney, Melbourne, and Brisbane are located. About 80% of Australia is arid or semi-arid desert,[14] which as explained above makes for such a great location for preservation of asteroid impact craters.