Impact winter and the Cretaceous/Tertiary extinctions: results of a Chicxulub asteroid impact model.
Earth Planet Sci Lett
; 128: 719-25, 1994.
Article
em En
| MEDLINE
| ID: mdl-11539442
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.
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Base de dados:
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Assunto principal:
Paleontologia
/
Atmosfera
/
Evolução Planetária
/
Aerossóis
/
Geologia
/
Modelos Químicos
País/Região como assunto:
Mexico
Idioma:
En
Revista:
Earth Planet Sci Lett
Ano de publicação:
1994
Tipo de documento:
Article
País de afiliação:
Estados Unidos
País de publicação:
Holanda