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Chicxulub asteroid impact
66 million years ago· Event· Earth, climate & extinctions
Well establishedStrong fossil, genetic or geological evidence.
An asteroid about 10 kilometers wide struck Mexico's Yucatán coast 66 million years ago, triggering the K–Pg extinction.
See it on the Life map →What happened
The asteroid hit a shallow sea at roughly 20 kilometers per second and blasted a crater about 180 kilometers across, now buried under younger rock near the town of Chicxulub. It vaporized sulfur-rich rock, filling the upper atmosphere with droplets, dust and soot that dimmed sunlight for years. Plants and plankton stopped growing, and food chains collapsed on land and at sea. Wildfires, tsunamis and acid rain added to the damage.
Why it matters
It is the best-documented cause of a mass extinction, and it showed that rare cosmic accidents, not only slow change, can redirect the history of life.
The evidence (fossils, genes, rocks)
Iridium and shocked quartz in boundary clay worldwide, impact glass beads, the buried crater found in Mexican oil-company surveys (confirmed 1991) and cores drilled into it in 2016.
Still debated
How long darkness lasted, and which effect killed most, is still modeled. A 2024 study traced it to a carbon-rich asteroid from beyond Jupiter; the Curious Science map covers the solar system.
Inside this (1)
Connections (4)
▸Chicxulub asteroid impact caused K–Pg extinction: end of the non-bird dinosaursWell established
The connection
The impact threw dust, soot and sulfur droplets high into the atmosphere. Sunlight dimmed for years, temperatures fell sharply in an 'impact winter', and photosynthesis on land and in the sea nearly stopped. With plants and plankton failing, food chains collapsed, killing roughly three-quarters of species, especially large animals and those reliant on fresh plant growth.
When and how
Yucatán Peninsula, Mexico, 66 million years ago, with effects worldwide within hours (fires, tsunamis) and lasting years (darkness and cold).
The evidence
The extinction and the impact debris lie in the same thin layer worldwide, dated as effectively simultaneous; climate models reproduce a lethal winter.
Debates and open questions
Which killing mechanism mattered most, soot from fires, sulfur droplets or fine rock dust, is debated; a 2023 study argued fine dust was the main sunlight blocker.
▸Deccan Traps eruptions may have been intensified by Chicxulub asteroid impactDebated
The connection
In 2015 Mark Richards, Paul Renne and colleagues proposed that seismic waves from the impact, equal to a magnitude 9 or larger earthquake, shook loose magma beneath India. On this view the Deccan Traps were already erupting, but the largest outpourings came soon after the impact.
When and how
Western India, within about 50,000 years after the impact 66 million years ago; proposed by a University of California, Berkeley team in 2015.
How sure are we?
Dating suggests eruption rates and lava styles changed near the impact, but dating precision of tens of thousands of years cannot prove cause and effect.
Debates and open questions
Other dating studies (2019) find eruption pulses that do not line up neatly with the impact, so the trigger idea remains unproven.
▸Iridium layer at the K–Pg boundary was the first clue to Chicxulub asteroid impactWell established
The connection
The iridium spike implied that an asteroid about 10 kilometers wide had struck Earth, but in 1980 no crater of the right age was known. The search narrowed when thick impact debris and tsunami deposits turned up around the Gulf of Mexico, leading to a buried crater at Chicxulub, confirmed in 1991.
When and how
From Gubbio, Italy (1980) to Yucatán, Mexico, where Pemex geophysicists Glen Penfield and Antonio Camargo had noted a buried ring in 1978; Alan Hildebrand's team confirmed it in 1991.
The evidence
Melt rock from the crater has the same age as the boundary layer, and impact glass beads found in Haiti match the crater's chemistry.
Debates and open questions
A few scientists argued for several impacts or volcanic iridium; these are now minority views, though smaller craters of roughly similar age, in Ukraine and off West Africa, are still examined.
▸Luis & Walter Alvarez predicted Chicxulub asteroid impactWell established
The connection
An asteroid big enough to spread iridium worldwide should have left a crater roughly 100–200 kilometers wide, yet none of the right age was known. Shocked quartz, tsunami deposits and glass beads found around the Gulf of Mexico narrowed the search. In 1991 a buried structure under Mexico's Yucatán coast was identified as the crater, matching the prediction.
When and how
Geophysicists Glen Penfield and Antonio Camargo, working for Mexico's state oil company Pemex, noticed the buried ring in 1978; Alan Hildebrand and colleagues confirmed it as an impact crater in 1991.
The evidence
Argon dating shows the crater and the boundary clay are the same age, about 66 million years; cores drilled in 2016 recovered shocked and melted rock.
Debates and open questions
Whether the impact alone caused the extinction or worked together with India's Deccan Traps eruptions.