Nadir Crater Confirmed: Second Major Asteroid Impact Linked to Dinosaur Extinction

The Atlantic’s Hidden Scar: A 66-Million-Year-Old Impact

Scientists have confirmed the existence of a massive, submerged asteroid impact structure—now known as the Nadir Crater—located deep beneath the Atlantic Ocean floor. This discovery is not merely a geological curiosity; its timing, precisely 66 million years ago, places it squarely in the window of the catastrophic Cretaceous-Paleogene (K-Pg) extinction event that wiped out the non-avian dinosaurs.

Located approximately 300 meters (nearly 1,000 feet) beneath the seabed off the coast of West Africa, the Nadir Crater measures roughly 8.5 kilometers (5.3 miles) in diameter. While significantly smaller than the famous Chicxulub crater in Mexico, the Nadir structure provides compelling new evidence that the K-Pg boundary event may have involved more than a single impactor, fundamentally shifting our understanding of this pivotal moment in Earth’s history.

Dimensions and Location of the Nadir Crater

The Nadir structure was initially identified using high-resolution seismic reflection data—a technique typically employed by the oil and gas industry to map subsurface geology. The data revealed a complex, bowl-shaped depression with features characteristic of a hypervelocity impact, including a distinct central peak and terraced rim structure.

Key Physical Characteristics:

• Location: Approximately 400 kilometers (250 miles) off the coast of Guinea-Bissau and Mauritania in West Africa.
• Depth: The crater rim is buried 300 to 400 meters below the modern seafloor sediments.
• Width: The structure spans about 8.5 kilometers (5.3 miles).
• Impact Estimate: The object that created Nadir is estimated to have been an asteroid roughly 400 meters wide.

This size classification puts the Nadir impactor in the range capable of causing severe regional devastation, even if it was not the sole cause of the global extinction.

Cataclysmic Effects of the Atlantic Impact

While the Chicxulub impact caused global climate disruption, the Nadir impact would have unleashed localized, yet immense, destructive forces, particularly in the Atlantic basin. The sheer force of a 400-meter-wide asteroid hitting the ocean floor would have generated two immediate, catastrophic effects:

1. Seismic Shockwave

The impact would have generated a massive earthquake, estimated to be between Magnitude 6.5 and 7.0. This seismic activity would have destabilized the continental shelf and triggered widespread underwater landslides.

2. Mega-Tsunami

Perhaps the most terrifying immediate consequence would have been the displacement of vast amounts of water. Modeling suggests the impact would have created a mega-tsunami with initial wave heights exceeding 1,000 meters (3,300 feet) near the impact site. Even thousands of kilometers away, waves would have reached dozens of meters high, inundating coastal regions of the Americas and West Africa.

Implications for the K-Pg Extinction Event

The most significant aspect of the Nadir Crater is its age. Dating methods confirm it formed 66.0 million years ago, making it contemporaneous with the Chicxulub impact in the Yucatán Peninsula, Mexico, which is widely accepted as the primary driver of the K-Pg extinction.

This precise timing opens up two major scientific hypotheses regarding the end of the dinosaurs:

Hypothesis 1: The Multiple Impact Scenario

This theory suggests that Earth was struck by two (or possibly more) separate, unrelated asteroids within a short geological timeframe. While Chicxulub delivered the knockout blow, the Nadir impact—and potentially others—could have weakened global ecosystems, contributing to the overall environmental stress that led to the mass extinction.

Hypothesis 2: The Fragmentation Scenario

This theory posits that a single, much larger parent asteroid broke apart just before impact, possibly due to tidal forces or an earlier collision. The largest fragment created Chicxulub, while a smaller piece slammed into the Atlantic, forming Nadir. This scenario is supported by observations of comets and asteroids breaking up as they approach planets.

Regardless of which hypothesis proves correct, the discovery of Nadir Crater reinforces the idea that the K-Pg boundary was a period of intense cosmic bombardment, far exceeding the single-impact event previously assumed.

“The discovery of a second, contemporaneous impact crater raises profound questions about the nature of the K-Pg event,” stated one researcher involved in the study. “It suggests that the Earth may have been subjected to a cluster of impacts, either from a fragmented body or a shower of separate asteroids.”

How Scientists Uncovered the Hidden Scar

The Nadir Crater was not found through a dedicated search for impact structures. Instead, it was discovered serendipitously by geophysicists analyzing proprietary seismic data collected by commercial entities.

Seismic reflection data works by sending acoustic energy (sound waves) down through the water column and into the seafloor. Different geological layers reflect these waves back to the surface at varying speeds, allowing researchers to build a detailed, three-dimensional profile of the subsurface structure.

When researchers examined the data from the West African margin, the tell-tale signs of a complex impact crater were unmistakable: the distinct central uplift, the deep basin, and the surrounding disturbed layers of rock. Further analysis of the surrounding sediment layers allowed them to precisely date the moment of impact to 66 million years ago.

Key Takeaways

The confirmation of the Nadir Crater off the coast of West Africa provides critical new data for planetary science and paleontology. Here are the essential points:

• Dual Impact Evidence: The Nadir Crater, measuring 8.5 km wide, is the second major impact structure confirmed to have formed exactly 66 million years ago.
• Local Catastrophe: The impact would have generated a Magnitude 7.0 earthquake and a 1,000-meter-high mega-tsunami in the Atlantic basin.
• Scientific Debate: Its existence supports either the theory of multiple, simultaneous impacts or the fragmentation of the Chicxulub parent body.
• Discovery Method: The structure was identified using existing seismic reflection data, highlighting the value of commercial geological surveys for pure scientific discovery.

What’s Next for Nadir Research

Confirmation of the Nadir Crater is only the first step. The next critical phase involves drilling directly into the structure. Scientific drilling expeditions are currently being planned for the coming years (likely in 2026 or 2027) to retrieve core samples from the crater floor and rim.

These samples will allow researchers to:

1. Confirm the Impact: Look for physical evidence of shock metamorphism and high-pressure minerals, definitively proving its impact origin.
2. Refine the Timing: Obtain more precise radiometric dating to confirm if the Nadir impact occurred hours, days, or months before or after Chicxulub.
3. Analyze Impact Materials: Determine the composition of the impactor, which could help confirm or refute the fragmentation theory by comparing it to Chicxulub material.

Understanding the precise sequence of events 66 million years ago is crucial to modeling how planetary ecosystems respond to extreme, multi-faceted environmental shocks.