Iridium layer and impact hypothesis for the K-Pg extinction
Capa de iridio e hipótesis del impacto de la extinción K-Pg
- Date
- 1980 · confidence high
- Place
- Gubbio, Italy (Bottaccione Gorge)
- Credited to
- Luis Alvarez, Walter Alvarez, Frank Asaro, Helen Michel
- People
- 👤 Frank Asaro1927–2014👤 Helen Vaughn Michel1932–👤 Luis Walter Álvarez1911–1988👤 Walter Alvarez1940–
- Field
- Cosmos & Earth
What was discovered
In the Cretaceous-Palaeogene boundary clay at Gubbio, the Alvarezes found iridium 30 times above normal, an element rare in the crust but abundant in asteroids. They proposed that a 10 km impact caused the extinction of the dinosaurs 66 million years ago.
Coordinates of the Bottaccione gorge, where the sample was taken. Initially highly controversial; the iridium layer was later found at more than 100 sites worldwide.
What it led to
- Search for and discovery of the Chicxulub crater
- Modern catastrophism in geology
- Near-Earth asteroid monitoring programmes
- Concept of nuclear winter
Built on
- Geologic time scale1822-1841
- Dating of the K-Pg boundary
Made possible
- The 'Big Five' mass extinctions1982
- Neutron activation analysis in geology
- Planetary defence (DART mission, 2022)