Leslie Massey
Australia has been the target of numerous asteroid impacts, with researchers at the University of New South Wales (UNSW) believing they have found evidence of the world's largest asteroid impact crater in the country, located near the town of Deniliquin in New South Wales. This discovery could have major implications for our understanding of the planet's history and the origin of life on Earth. The asteroid strike is estimated to have occurred around 66 million years ago, coinciding with a mass extinction event that wiped out 85% of the world's species, including non-avian dinosaurs. The structure, known as the Deniliquin structure, is thought to have been formed on the eastern part of the Gondwana continent before it split into several continents, including Australia.
| Characteristics | Values |
|---|---|
| Location | Near the town of Deniliquin, New South Wales, Australia |
| Size | Almost three times larger than the asteroid that wiped out the dinosaurs |
| Age | 66 million years old |
| Crater | Contains an uplifted core |
| Cause | Asteroid strike |
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What You'll Learn
The world's largest asteroid impact crater is in Australia
Researchers at the University of New South Wales (UNSW) believe they have found the world's largest asteroid impact crater in Australia. The structure, known as the Deniliquin structure, is located near the town of Deniliquin in southern New South Wales. It is thought to be almost three times larger than the asteroid impact crater that wiped out the dinosaurs.
The discovery of the Deniliquin structure is based on geophysical evidence suggesting the existence of a massive, magnetized structure deep beneath the earth in southeast Australia. This structure is believed to be the result of an asteroid impact that occurred when the eastern part of the Gondwana continent existed, before it split into several continents, including Australia.
The Deniliquin structure is not easily identifiable as a typical asteroid impact crater due to erosion and sediment movement over time. However, researchers have identified it as an impact crater based on its central uplifted dome, a key characteristic of large impact structures. This dome is similar to the splash of water that occurs when a pebble is dropped into a pool, creating a transient crater.
While the Deniliquin structure is believed to be the largest asteroid impact crater, there is some debate within the scientific community. Louis Moresi from the Australian National University suggests that the structure could have been formed by the collision of two landmasses, similar to the formation of a mountain range.
The discovery of the Deniliquin structure adds to the growing body of evidence that the Australian continent and its predecessor, Gondwana, have been the target of numerous asteroid impacts. These impacts have played a significant role in shaping the geological history of our planet and may even have triggered major events such as glaciation and mass extinctions.
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The Deniliquin structure in New South Wales
The Deniliquin structure is a massive, magnetized impact structure located in southern New South Wales, Australia. It is believed to be the largest asteroid impact crater in the world, with a diameter of up to 520 kilometres. The structure is buried deep beneath the earth and has not yet been fully explored or drilled.
The Deniliquin structure is thought to have been formed by a meteor strike between 445 and 443 million years ago, during the Hirnantian glaciation stage. This period was a mass extinction event that eliminated about 85% of Earth's species. The impact of the asteroid created a crater with an uplifted core, similar to the splash of a drop of water when a pebble is dropped into a pool. Over time, the central dome created by the impact may have eroded or become buried, making it difficult to identify.
The discovery of the Deniliquin structure is based on geophysical data obtained from the surface. To confirm the impact origin of the structure, further evidence is needed, such as physical proof of shock, which can only be obtained by drilling deep into the structure. The structure is located in a flat plain developed over up to 300 meters of flat-lying Cainozoic strata belonging to the roughly circular Murray Basin.
The town of Deniliquin, for which the structure is named, is located in the western Riverina region of southwestern New South Wales, close to the border with Victoria. It is the largest town in the Edward River Council local government area and is known for its agricultural industries, including dairy, rice, wool, and timber. The town is divided by the Edward River, a tributary of the Murray River, and is home to approximately 6,400 people.
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The Alvarez hypothesis and asteroid strikes
The Alvarez hypothesis, first proposed in 1980 by the father-son team of scientists Luis and Walter Alvarez, suggests that the mass extinction of non-avian dinosaurs and many other living things during the Cretaceous-Paleogene extinction event was caused by the impact of a large asteroid on Earth. The asteroid is believed to have struck the Yucatán Peninsula in Mexico, at Chicxulub, causing a cataclysmic event that ended the reign of the dinosaurs and paved the way for the ascension of mammals.
The Alvarez team's research focused on studying the abundances of rare earth elements (REE) in clay layers found at the K/T boundary in the Umbrian Apennines (Gubbio section) in Northern Italy. They discovered anomalies in the abundances of several REEs, with a particularly notable increase in the concentration of iridium (Ir). Iridium is typically found in minuscule quantities in the Earth's crust, but it is more common in extraterrestrial objects like asteroids. The Alvarez team's findings indicated a concentration of iridium in the clay layers that was 2 to 3 orders of magnitude higher than expected, suggesting that the cause of the extinction event was a meteorite impact.
The hypothesis gained further support with the discovery of the impact site, the Chicxulub Crater, a 180-kilometer-wide and 20-kilometer-deep structure buried beneath a kilometer of Tertiary carbonates. This provided the "smoking gun" evidence that an asteroid impact of this magnitude could indeed have caused the mass extinction. The impact would have generated a destructive blast thousands of times more powerful than all the world's nuclear weapons combined, triggering earthquakes, tsunamis, and a global blanket of dust and debris that would have devastated the climate and food chain.
In recent years, new evidence has emerged suggesting the existence of an even larger asteroid impact structure buried deep in southeast Australia, specifically in southern New South Wales. This structure, known as the Deniliquin structure, spans up to 520 kilometres in diameter and is yet to be fully confirmed through drilling. If verified, it would surpass the Chicxulub crater in size and provide further insight into the Earth's evolutionary history and the potential impact of asteroid strikes.
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Asteroids and the predecessor continent Gondwana
The existence of Gondwana, a predecessor continent, was first hypothesised in the mid-1800s by Eduard Suess, a Viennese geologist. He named it "Gondwanaland", after the Gondwana region of central India, where geological formations match those of a similar age in the southern hemisphere. Gondwana was a large landmass, often referred to as a supercontinent. It was formed by the accretion of several cratons (large stable blocks of the Earth's crust). The remnants of Gondwana make up around two-thirds of today's continental area, including South America, Africa, Antarctica, Australia, Zealandia, Arabia, and the Indian subcontinent.
Gondwana was assembled by continental collisions in the Late Precambrian (about 1 billion to 542 million years ago) and was fully assembled by the Late Precambrian, some 600 million years ago. The first stage of its breakup began in the Early Jurassic Period, about 180 million years ago. During this time, Africa and South America broke apart from the other half of Gondwana. About 140 million years ago, South America and Africa split, opening up the South Atlantic Ocean between them. Meanwhile, on the eastern half of Gondwana, Madagascar made a break from India and both moved away from Australia and Antarctica. Australia and Antarctica clung together longer; their final split was about 45 million years ago.
The Deniliquin structure, an asteroid impact site in New South Wales, Australia, is believed to be located on the eastern part of the Gondwana continent before it split off into several continents, including Australia. The Deniliquin structure, yet to be further tested by drilling, spans up to 520 kilometres in diameter. This exceeds the size of the Vredefort impact structure in South Africa, which has been considered the world's largest. The discovery of the Deniliquin structure is huge, as it could be evidence of the world's largest asteroid impact crater, with vast consequences.
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The oldest meteorite impact crater in Western Australia
The world's oldest meteorite impact crater has been discovered in Western Australia, in the Pilbara region of northwestern Australia. The crater, which is estimated to be at least 100 km (62 miles) wide, was formed more than 3.5 billion years ago, making it the oldest known impact crater by more than a billion years. The discovery was made by geologists from Curtin University and the Geological Survey of Western Australia (GSWA), who had predicted the crater's location based on a theory about how Earth's early continents formed.
The crater was identified through the presence of "shatter cones", geological features that form only under extreme pressures, such as those created by meteorite impacts or underground nuclear explosions. These shatter cones were found in the ancient rocks of the Pilbara region, specifically in the Antarctic Creek Member of the rocks. The discovery of the Pilbara crater supports the idea that meteorite impacts played a significant role in the geological history of the planet, similar to their impact on the Moon and other celestial bodies.
The impact that created the Pilbara crater is estimated to have been caused by an object travelling at more than 36,000 km/h (22,000 mph), resulting in destruction on a global scale. The energy released by such an impact may have contributed to the formation of Earth's early continents and the evolution of the planet. The discovery highlights the potential for finding more ancient craters in the cores of continents, which could transform our understanding of early Earth and the origins of life.
In addition to the Pilbara crater, there is evidence of other asteroid impacts in Australia. For example, researchers at the University of New South Wales (UNSW) believe they have found evidence of the world's largest asteroid impact crater near the town of Deniliquin, Australia. This impact may have triggered a major glaciation event that led to the extinction of 85% of the world's species. The Deniliquin structure is believed to have been located on the eastern part of the Gondwana continent, which later split into several continents, including Australia.
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Frequently asked questions
Researchers believe that the world's largest asteroid impact crater is buried deep in southeast Australia, specifically in southern New South Wales near the town of Deniliquin.
When an asteroid strikes, it creates a crater with an uplifted core. This is similar to how a drop of water splashes upward when a pebble is dropped into a pool. This central uplifted dome is a key characteristic of large impact structures.
Researchers at the University of New South Wales (UNSW) found evidence of the asteroid's impact through the presence of shatter cones, a type of rock formation found in the Pilbara region's North Pole Dome area.
