The Nadir Crater and The Asteroids That Changed Earth’s History
The discovery of a five-mile-wide crater off the coast of West Africa suggests that the asteroid that wiped out the dinosaurs 66 million years ago may not have acted alone.
This smaller impact crater, identified through advanced seismic imaging technology, is believed to have been formed by a secondary asteroid, a cosmic sibling to the one that created the infamous Chicxulub crater in Mexico, which measures about 160 km (100 miles) wide and responsible the start of the Cenozoic period; the ‘age of the mammals’.
Marine geologists estimate that this lesser-known impact occurred within 2 million years of the Chicxulub event. While it was not as catastrophic as its colossal counterpart, it was still powerful enough to cause thousands of miles of underwater landslides and trigger a 2,000-foot tsunami.
After the impact, the force shook the ground so violently that the seabed turned almost liquid, creating cracks and gullies, and even triggering massive tsunamis. The crater left behind is about 9.2 km wide, with the damage spreading well beyond the crater’s edge.
In the center of the crater, the ground was pushed up, forming a peak, while the surrounding land collapsed inward to fill the hole left by the impact.
Scientists think the space rock hit from the east, and the impact caused everything to change in just a few seconds to minutes, leaving behind a clear record of the event in the rock layers below.
The new seismic imaging data offers the most detailed mapping yet of this crater, standing nearly 1,000 feet deep. Although it doesn’t carry the same fame as the asteroid believed to be responsible for the mass extinction of the dinosaurs, this discovery emphasizes that Earth’s history is peppered with asteroid impacts, each leaving its own mark on the planet.
The implications of this second crater are significant: It raises the possibility that Earth was struck by multiple asteroids or comets around the same time, potentially contributing to the Cretaceous-Paleogene extinction.
Using 3D seismic data to image an impact crater in exceptional detail, allows reconstruction for how the crater formed and the destructive power of these impacts. Intense seismic activity reveals massive tsunamis that followed the impact, providing valuable information about the environmental consequences.
If linked to the Chicxulub event, the Nadir Crater indicates these impacts together triggered the global environmental changes that led to mass extinction, shaping the rise of mammals.
This discovery opens new doors for studying ancient impacts and their planet-altering effects.
Craters in Australia
Australia, with its vast and ancient landscapes, is no stranger to asteroid impacts. The country is home to several notable craters, each telling its own story of Earth’s violent cosmic history.
One of the most famous is the Wolfe Creek Crater in Western Australia. Formed about 300,000 years ago, it spans roughly 875 metres across and is one of the best-preserved impact craters on Earth. The crater was created by a meteorite weighing more than 50,000 tonnes, hurtling toward the planet at tens of thousands of kilometres per hour.
Another well-known site is the Gosses Bluff Crater, also known as Tnorala to the Western Arrernte people. Located in the Northern Territory, Gosses Bluff is thought to have been formed about 142 million years ago by a comet or asteroid impact. The initial diameter of the crater was around 22 kilometres, though erosion has since reduced its size to about 5 kilometres.
In South Australia, the Lake Acraman site offers one of the oldest known impact structures, dating back approximately 580 million years. While the original crater is eroded and submerged under Lake Acraman, it is estimated that the asteroid that struck the region was over 4 kilometres in diameter, causing immense destruction across the continent.
These craters are a reminder that, just as in the case of the West African crater, Earth has always been vulnerable to extraterrestrial impacts and scars left by these collisions offer insights into the planet’s history and the powerful forces that have shaped its evolution.
Global Impact and Future Risks
The discovery of a second crater from the same era as the Chicxulub impact raises questions about how many more asteroids may have struck Earth during that time.
While the Chicxulub asteroid is credited with causing the mass extinction that ended the reign of the dinosaurs, smaller impacts like the one off the coast of West Africa may have contributed to the overall environmental upheaval, further pushing species toward extinction.
Asteroid impacts have the potential to cause significant damage, not just at the impact site but globally. The energy released by these collisions can trigger wildfires, tsunamis, and even long-lasting climate changes. The dust and debris thrown into the atmosphere by an impact can block sunlight, leading to a dramatic cooling of the planet – a phenomenon known as an “impact winter.”
Scientists now actively monitor Near-Earth Objects (NEOs) to track potential threats, history has shown that even smaller asteroids can have massive consequences. Understanding past impacts, like the recently discovered West African crater, helps researchers better predict and prepare for future risks. It also underscores the importance of continued investment in space observation and planetary defence initiatives.
Australian Asteroid Research
Australia’s relatively stable geology make it an ideal location for studying impact craters. Several Australian universities and research institutions are actively involved in global efforts to study asteroids and track potential threats.
The Desert Fireball Network, led by Curtin University, is one such initiative. This network of cameras tracks fireballs as they streak across the sky, providing valuable data about meteorites and their potential impact zones.
Australia also plays a role in planetary defence, working with international organisations to detect and track asteroids that could pose a risk to Earth.
Studying both ancient craters and modern asteroids, researchers in Australia and around the world are better equipped to understand the long-term effects of cosmic impacts and how to mitigate future risks.
While the asteroid that killed the dinosaurs remains the most famous celestial visitor in Earth’s history, discoveries like the smaller crater off the coast of West Africa reveal that it wasn’t acting alone.
These findings deepen our understanding of Earth’s tumultuous past and reinforce the ongoing need to study and prepare for potential future asteroid impacts. Australia, with its rich history of impacts and active role in asteroid research, remains a key player in this vital field of study.
