The Alvarez impact hypothesis is published
Luis Alvarez, Walter Alvarez, Frank Asaro and Helen Michel published in Science the measurement of anomalously high iridium in the boundary clay at Gubbio and Stevns Klint, and the inference that a body about ten kilometres across had struck the Earth and injected enough dust into the stratosphere to suppress photosynthesis. The paper is unusual in that its central evidence is a single element abundance rather than a fossil or a structure, and the argument depends on a fact about planetary differentiation rather than about biology. It was resisted for most of the following decade, partly because no crater was known, partly because it looked like catastrophism, and partly because sampling of the fossil record near the boundary appeared at the time to show a gradual decline — an appearance later attributed in large measure to the difficulty of sampling the last occurrence of a rare species.
Historical — it happened, and the record is settled.
Subjects
- The Cretaceous–Palaeogene iridium anomaly · geological and soil phenomenon · Global · not located
- Bottaccione Gorge, Gubbio · site · Italy
- Walter Alvarez · person · United States · not located
Evidence
Partly verified — Core facts are sourced; some optional detail is deliberately absent.
Extraterrestrial Cause for the Cretaceous–Tertiary Extinction
Supports the iridium anomaly at Gubbio and Stevns Klint, the siderophile-depletion reasoning and the inference of an impactor about ten kilometres across. V55 verification basis: this session had no network access to any source — WebFetch was egress-blocked and the WebSearch budget was exhausted — so the cited work was not retrieved and its pagination was not re-checked. Volume and page range are quoted from standing knowledge and were not re-checked.
Science · 1980 · Partly verified
Alvarez, L. W., Alvarez, W., Asaro, F. and Michel, H. V., Science, vol. 208 (1980), pp. 1095–1108
Recorded on The Cretaceous–Palaeogene iridium anomaly
- The Alvarez impact hypothesis is published
- Chicxulub is identified as the K–Pg impact crater
Related
Related because they share a subject in the Atlas — never because the text looks similar.