The Tyrannosaurus rex was a massive carnivore, reigning over the landscape of what is now western North America right up to the end of the Cretaceous period 66 million years ago. The sudden and complete disappearance of this dominant lineage, along with nearly three-quarters of all plant and animal species, has long puzzled researchers. Science now widely accepts the theory that the demise of the non-avian dinosaurs, including the T. rex, was the result of a catastrophic asteroid impact, known as the Cretaceous-Paleogene (K-Pg) extinction event.
The Initial Catastrophe
The catastrophe began when a massive asteroid, estimated to be between 10 and 15 kilometers (6 to 9 miles) in diameter, slammed into the shallow seas of the Yucatán Peninsula in modern-day Mexico. This hypervelocity collision instantly excavated the 180-kilometer-wide Chicxulub crater, releasing an estimated 100 million megatons of energy. The force generated a seismic pulse roughly equivalent to a Magnitude 10 earthquake, causing massive landslides and shockwaves that traveled across the globe.
Within minutes of the strike, a thermal pulse of intense heat radiated outward, igniting widespread firestorms across North America. Superheated winds, moving in excess of 1,000 kilometers per hour, scoured the nearby landscape, shredding vegetation and life within a radius of 900 to 1,800 kilometers of the impact site. The impact also displaced an immense volume of water, generating colossal tsunamis that reached estimated heights of 50 to 150 meters along coastlines around the Gulf of Mexico.
The Global Extinction Mechanism
The global extinction mechanism began when the impact launched trillions of tons of pulverized rock, dust, and soot high into the atmosphere, creating a massive ejecta plume that circulated worldwide. Because the asteroid struck a region rich in sulfur-bearing gypsum rock, enormous quantities of sulfur were vaporized and injected into the stratosphere.
These fine particles of dust, soot, and sulfate aerosols formed a thick, persistent global cloud that blotted out the sun, triggering a rapid and prolonged environmental collapse known as “impact winter.” The resulting darkness drastically reduced the amount of sunlight reaching the Earth’s surface for months, if not years. This sustained reduction in light caused photosynthesis to cease almost entirely, killing off the base of the food chain, including plants on land and phytoplankton in the oceans.
The atmospheric sulfate aerosols also initiated a rapid drop in global temperatures, plunging the planet into freezing conditions. This sudden, severe cooling, combined with the collapse of plant life, created a desolate world where most large animals could not survive. The resulting lethal domino effect moved up the food web, leading to mass starvation.
Geological Proof of Impact
The impact hypothesis is supported by distinct markers preserved in the geological record across the planet, known as the K-Pg boundary layer. This thin layer of sediment, dating back exactly 66 million years, contains an anomalously high concentration of the element Iridium. Since Iridium is extremely rare in the Earth’s crust but abundant in asteroids, this provides direct evidence of an extraterrestrial source.
The boundary layer also contains microscopic evidence of the immense shock pressure generated by the collision. Samples taken globally show the presence of shocked quartz, which are grains of quartz crystal exhibiting deformation features created only by extreme impact pressures. Further confirmation comes from the discovery of small, weathered glass beads called tektites, which are molten rock droplets ejected from the impact site that cooled rapidly in flight.
The Chicxulub crater itself is a massive subsurface structure centered on the Yucatán Peninsula. Geophysical surveys, including gravity mapping, have revealed the crater’s immense, 180-kilometer-wide ring structure. Drilling operations within the crater have recovered layers of impact melt rock and suevite, definitively linking the structure to the K-Pg boundary.
The T. Rex and the End of an Era
The global collapse of the food chain sealed the fate of the Tyrannosaurus rex population. As an apex predator, the T. rex required vast quantities of meat, but the herbivores it preyed upon, such as Triceratops and hadrosaurs, depended entirely on abundant plant life.
When the sun-blocking cloud caused plant life to die off, the herbivore populations quickly starved. This catastrophic loss of primary consumers meant that the T. rex’s food source vanished, causing the extinction to cascade up the food web. The sheer size of the T. rex became a liability, as smaller, generalist scavengers and omnivores were better equipped to survive in the resource-scarce post-impact world. The extinction of the T. rex and all other non-avian dinosaurs created ecological vacancies that allowed surviving groups, particularly the mammals, to diversify and usher in the Cenozoic Era.