Extinction Simulator

Explore what happened when the asteroid hit

Step through the K-Pg extinction event timeline — from impact to nuclear winter to recovery. Adjust parameters to see how different scenarios would have affected survival rates.

K-Pg Extinction Timeline

Species Survival Rate

Key Facts About the K-Pg Extinction

Date

66 million years ago

Asteroid Size

~10-15 km diameter

Impact Location

Chicxulub, Yucatan, Mexico

Species Lost

~75% of all species

How to Use

1
Select an impact scenario
Choose from the scientific consensus Chicxulub scenario or adjust impactor size, angle, and composition using the parameter sliders to explore how variations would change the immediate and long-term effects.
2
Step through the timeline
Use the forward and back buttons to move through the post-impact sequence: ejecta fallout, wildfires, impact winter, acid rain, and eventual recovery, with estimated duration for each phase.
3
Read the survival outcomes
Each phase shows which major groups are predicted to survive or be eliminated based on their ecological requirements, body size, geographic distribution, and dietary flexibility.

About

The Cretaceous-Palaeogene boundary, dated to 66.043 million years ago by high-precision radiometric dating, marks one of the most abrupt biological transitions in the history of life. The discovery of the global iridium anomaly by Luis and Walter Alvarez in 1980 provided the first strong evidence for an extraterrestrial cause, and subsequent identification of the Chicxulub crater in 1991 confirmed the impact hypothesis. The boundary is now one of the most intensively studied intervals in the geological record.

Mass extinctions are not instantaneous events — they unfold across timescales ranging from years to tens of thousands of years. The immediate physical effects of the Chicxulub impact (thermal pulse, ejecta, pressure wave) were global but brief. The prolonged effects — impact winter from aerosols and soot, collapse of primary productivity, disruption of marine carbonate chemistry — played out over years to decades. Recovery of ecosystem complexity took millions of years, with the Palaeocene fauna looking markedly impoverished compared to the Late Cretaceous.

The extinction simulator incorporates results from published climate modelling studies, palaeontological occurrence data at the K-Pg boundary, and comparative survival analyses. By adjusting parameters such as impactor size and composition, users can explore how sensitive the outcome would have been to different initial conditions, building intuition for the contingency of evolutionary history and the mechanisms by which mass extinctions selectively remove some lineages while sparing others.

FAQ

What caused the end-Cretaceous mass extinction?

The scientific consensus, supported by multiple independent lines of evidence, identifies the Chicxulub bolide impact as the primary cause. The impact site, buried beneath the Yucatan Peninsula, left a 180-kilometre crater. Global evidence includes the iridium anomaly (iridium is rare in Earth's crust but common in meteorites) exactly at the Cretaceous-Palaeogene boundary, shocked quartz grains indicating high-pressure impact metamorphism, and spherule layers representing solidified ejecta droplets. The Deccan Traps volcanism in India was occurring simultaneously and may have contributed to environmental stress.

Why did birds survive when non-avian dinosaurs did not?

Several factors likely contributed. Body size was critical: all non-avian dinosaurs that survived the end-Cretaceous had body masses below roughly 25 kilograms, consistent with the known size distribution of Cretaceous birds. Smaller body size reduces absolute food requirements. Dietary flexibility also matters: seed-eating birds could subsist on seeds stored in soils long after photosynthesis collapsed. Ground-nesting versus tree-nesting may have been relevant given forest destruction. No single factor provides a complete explanation — survival was probably determined by a combination of traits.

How long did the impact winter last?

Modelling studies estimate that soot from global wildfires and sulfate aerosols from vaporised anhydrite at the impact site caused surface cooling of roughly 15 to 20 degrees Celsius for up to a decade, with reduced sunlight suppressing photosynthesis. Recovery of global temperatures to near pre-impact levels took several decades to centuries depending on the model. The biological effects outlasted the physical effects because food web restructuring is slow and because recovery of primary productivity required re-establishment of plant communities.

Which groups other than non-avian dinosaurs went extinct at the K-Pg boundary?

The end-Cretaceous event was one of the five largest mass extinctions in the Phanerozoic. In marine environments, ammonites, mosasaurs, and plesiosaurs disappeared entirely. Non-avian pterosaurs also went extinct. On land, many mammal lineages, lizard groups, and plant families were eliminated or severely reduced. Freshwater ecosystems were comparatively resilient, which partly explains why crocodilians, turtles, and freshwater fish survived. Overall, roughly three-quarters of species on Earth are estimated to have gone extinct within a geologically brief interval.

Could the impact have been survived if it had hit a different location?

Geologically, the Yucatan target was particularly unfortunate. The impact struck thick deposits of anhydrite (calcium sulfate), which vaporised to produce sulfur dioxide aerosols responsible for much of the cooling and acid rain. Had the same impactor struck deep-ocean crust instead, sulfate aerosol production would have been substantially lower and the climatic effects potentially less severe. Simulations suggest that a different impact site could have reduced extinction severity, though the immediate blast effects would still have been catastrophic on a regional scale.