Impact winter and the Cretaceous/Tertiary extinctions: results of a Chicxulub asteroid impact model

Earth Planet Sci Lett. 1994:128:719-25. doi: 10.1016/0012-821x(94)90186-4.


The Chicxulub impact crater in Mexico is the site of the impact purported to have caused mass extinctions at the Cretaceous/Tertiary (K/T) boundary. 2-D hydrocode modeling of the impact, coupled with studies of the impact site geology, indicate that between 0.4 and 7.0 x 10(17) g of sulfur were vaporized by the impact into anhydrite target rocks. A small portion of the sulfur was released as SO3 or SO4, which converted rapidly into H2SO4 aerosol and fell as acid rain. A radiative transfer model, coupled with a model of coagulation indicates that the aerosol prolonged the initial blackout period caused by impact dust only if the aerosol contained impurities. A larger portion of sulfur was released as SO2, which converted to aerosol slowly, due to the rate-limiting oxidation of SO2. Our radiative transfer calculations, combined with rates of acid production, coagulation, and diffusion indicate that solar transmission was reduced to 10-20% of normal for a period of 8-13 yr. This reduction produced a climate forcing (cooling) of -300 Wm-2, which far exceeded the +8 Wm-2 greenhouse warming, caused by the CO2 released through the vaporization of carbonates, and therefore produced a decade of freezing and near-freezing temperatures. Several decades of moderate warming followed the decade of severe cooling due to the long residence time of CO2. The prolonged impact winter may have been a major cause of the K/T extinctions.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Aerosols / chemistry*
  • Atmosphere*
  • Biological Evolution
  • Carbon Dioxide
  • Dust
  • Evolution, Planetary*
  • Geologic Sediments
  • Geological Phenomena
  • Geology*
  • Greenhouse Effect
  • Mexico
  • Minor Planets
  • Models, Chemical*
  • Paleontology*
  • Sulfur Dioxide / chemistry
  • Sulfur Oxides / chemistry
  • Sulfuric Acids / chemistry


  • Aerosols
  • Dust
  • Sulfur Oxides
  • Sulfuric Acids
  • Sulfur Dioxide
  • Carbon Dioxide
  • sulfur trioxide