isotopic dating lead to some uncertainty. Other Triassic craters are closer to the Triassic–Jurassic boundary but also much smaller than the Manicouagan reservoir. The eroded Rochechouart impact structure in France has most recently been dated to million years ago, but at across (possibly up to across originally), it appears to be too small to have affected the ecosystem. Other putative or confirmed Triassic craters include the wide Puchezh-Katunki crater in Eastern Russia (though it may be Jurassic in age), the wide Saint Martin crater in Manitoba, the wide Obolon' crater in Ukraine, and the wide Red Wing Creek structure in North Dakota. Spray et al. (1998) noted an interesting phenomenon, that being how the Manicouagan, Rochechouart, and Saint Martin craters all seem to be at the same latitude, and that the Obolon' and Red Wing craters form parallel arcs with the Rochechouart and Saint Martin craters, respectively. Spray and his colleagues hypothesized that the Triassic experienced a "multiple impact event", a large fragmented asteroid or comet which broke up and impacted the earth in several places at the same time. Such an impact has been observed in the present day, when Comet Shoemaker-Levy 9 broke up and hit Jupiter in 1992. However, the "multiple impact event" hypothesis for Triassic impact craters has not been well-supported; Kent (1998) noted that the Manicouagan and Rochechouart craters were formed in eras of different magnetic polarity, and radiometric dating of the individual craters has shown that the impacts occurred millions of years apart. Volcanic eruptions Massive volcanic eruptions, specifically the flood basalts of the Central Atlantic Magmatic Province (CAMP), would release carbon dioxide or sulfur dioxide and aerosols, which would cause either intense global warming (from the former) or cooling (from the latter). The rate of carbon dioxide emissions was one of the most meteoric rises in carbon dioxide levels in Earth's entire history; the extreme severity of the mass extinction event can be attributed to the breakneck rate of CAMP carbon dioxide emissions as well as their humongous quantity. It is estimated that a single volcanic pulse from the large igneous province would have emitted an amount of carbon dioxide roughly equivalent to projected anthropogenic carbon dioxide emissions for the 21st century. The catastrophic dissociation of gas hydrates, which has been suggested as one possible cause of the largest mass extinction of all time, the so-called "Great Dying" at the end of the