A February 2013 study using ultra-precise radiometric dating definitively confirmed the Chicxulub asteroid impact occurred exactly at the dinosaur extinction 66 million years ago, ending decades of debate.
The Study
Berkeley researchers dated tektites (impact glass) from the Chicxulub crater and volcanic ash from the K-T (now K-Pg) boundary layer - the geological marker of mass extinction. Both yielded the same age: 66,038,000 years ago, plus or minus 11,000 years. The timing was indistinguishable - impact and extinction were simultaneous.
The Debate
Since the 1980 discovery of an iridium-rich layer at the K-T boundary, scientists debated whether an asteroid alone caused the extinction or volcanic eruptions (India’s Deccan Traps) contributed. Some argued the impact preceded extinction by thousands of years. The 2013 study ended that debate - the impact’s timing precisely matched dinosaur disappearance.
The Impact
A 6-mile-wide asteroid struck the Yucatán Peninsula at 45,000 mph, releasing energy equivalent to 10 billion Hiroshima bombs. The impact vaporized rock, ejecting molten debris into space that rained globally as tektites. Wildfires ignited continents. Dust and sulfur aerosols blocked sunlight for years, collapsing photosynthesis.
The Victims
75% of species died, including all non-avian dinosaurs (birds survived), pterosaurs, marine reptiles (mosasaurs, plesiosaurs), and ammonites. Mammals, mostly small and nocturnal, survived and radiated into ecological niches dinosaurs once dominated. Without the asteroid, mammals might never have diversified - humans owe our existence to that impact.
Deccan Traps
The study found Deccan volcanic eruptions began before the impact and continued after, contributing to climate stress but not causing the extinction. The asteroid delivered the coup de grâce to ecosystems already weakened by volcanism and sea-level changes.
Modern Relevance
The finding underscores asteroids’ catastrophic potential. NASA’s Planetary Defense program searches for Earth-crossing asteroids and tested deflection with the 2022 DART mission - humanity’s first attempt to prevent a Chicxulub repeat.
Source: Science Chicxulub Dating