Ну вот к примеру ссылки и цитаты из них:
http://hcs.harvard.edu/~jus/0303/haggerty.pdfOur new compilation of published 40Ar/39Ar
age determinations of Mesozoic/Cenozoic flood basalts,
presented as Gaussian probability distributions, allows improved
estimates of the initiation time and duration of the
major flood basalt provinces. The age distributions of twelve
individual flood basalt episodes from the last 250 Myr suggest
that in most cases the eruption of the bulk of the voluminous
basalt flows took place in <1 Myr. Time series analysis
reveals equivocal evidence or a quasi-periodicity of 23
Myr.
The estimated initiation times of these continental flood
basalt eruptions are found to correlate with the independently
determined ages of mass extinctions of life at a confidence
level >97% (within the estimated errors in ages of
eruptions and extinctions). Projected environmental and climatic
effects of these mega-eruptions may be severe, and
flood basalt events may have played a large role in the
extinctions.
http://faculty.plattsburgh.edu/thomas.wolosz/volcanism.htmThe Deccan Traps in India consist of over 2,000,000 cubic kilometers of basaltic lava flows, in some areas reaching a thickness of over 2,400 meters. Estimates of annual basalt production range from 2 to 8 km.3 per year. The amount of lava of and by itself is not the feature that scientists are interested in. It is the amounts of various gases given off by these eruptions that are of interest. The current estimate is that during the formation of the Deccan Traps, the following amounts of gas were given off:
33 trillion tons of CO2
6.6 trillion tons of SO2
66 billion tons of fluorine and chlorine
The next question is the amount of time. If old estimates that the Deccan Traps were erupted over 5 million years or so are correct, then the effects of these gases is minimized. However, recent paleo-magnetic work on the Deccan Traps suggests that they were erupted over the space of only 500,000 years. If this were the case, then the amount of greenhouse gases added to the atmosphere in the form of CO2 and sulfur aerosols, plus the amount of acid rain generated would have had severe impacts on the environment.
Если 97% корреляция верна, то отвергать влияние трапповых извержений едва ли можно.
Что касается эффекта (вернее нескольких разных эффектов) извержения на биосферу, то они не обязательно должен был быть мгновенными и "прямыми".
Вот еще информация:
http://www.atmos.washington.edu/1998Q4/211/project2/group5.htmDue to their weight, the ash particles settle down to the ground in a matter of days. The ash particles have a low residence time because they remain in the troposphere. The sulfer gases emitted by the volcano combine with traces of water vapor in the atmosphere to form tiny sulfuric acid aerosols. These aerosols have a much longer residence time (a year or two) because they are injected into the stratosphere. The eruption of Krakatoa resulted in 294 million tons of sulfuric acid in the atmosphere.
Large volcanic eruptions such as Krakatoa cause a temporary global cooling effect. The earth cooled by about 2.5 degrees Celsius for one to two years after the eruption of Krakatoa. This is due to the amount and small size of the aerosols in the atmosphere. As efficient reflectors of sunlight, aerosols screen the ground from some of the solar radiation it would ordinarily receive from the sun. Thus when there is an excess of volcanic particles and aerosols in the atmosphere, they have a cooling effect on the earth. This was the case in Krakatoa which, in the year following the eruption, experienced its coolest year ever recorded.
