Trap volcanics do not emit great clouds of ash and sulphates, as do caldera volcanoes. They do emit huge amounts of CO2. And, when extruding on a continental shelf, will cause the release of the CH4 in any clathrates in the vicinity.
Methane Catastrophe
But Morante understood the isotopic excursion to have been the possible result of "the release of potentially huge volumes of 13C-depleted methane stored in clathrates in tundra environments and polar continental shelves," which, together with increased carbon dioxide released from continental shelf sediments, would have created a greenhouse world. In addition, Morante found that the negative carbon isotope excursion took between 300,000 and 600,000 years, making for a much shorter extinction event than that contemplated by Erwin. (As noted previously, we now know that major hydrate methane releases actually take place in less than 10,000 years.) Basing his estimate of the length of time needed for post-extinction recovery on the carbon isotope record, Morante placed the emergence of the planet from its end-Permian trauma at about the latest Middle Triassic, roughly ten million years later. Morante also recognized that the end of the Permian brought a reduction of global oceanic thermohaline circulation, though he did not specifically tie this to the hydrate methane release (Morante, 1993).
The continental margin methane proposal presented here and previously (Vermeij and Dorritie, 1996; Dorritie, 2002) incorporates some of the undisputed facts about the end-Permian world. It accepts that Siberian Traps volcanism had a powerful effect on Permian world climate. But rather than the Traps eruptions being the sole cause of the extinctions, it sees the Traps as having had an important role, though largely as a trigger for the release of hydrate methane and the free methane below. Traps eruptions facilitated this release in two ways: first, directly, by heating terrestrial permafrost and northern continental margin sediments. This direct heating would have been by lava flows, pyroclastic eruptions (superheated, ground-hugging, volcanic dust clouds), and ash falls, and would have led to the immediate release of methane from the affected areas. Traps volcanism would also have directly heated the seawater of the PaleoArctic Ocean (the northernmost part of Panthalassa; sometimes referred to as the Boreal Ocean), and that warmed water would have heated seafloor sediments and released methane from the continental margins across which it flowed. In addition, by injecting vast quantities of carbon dioxide into the atmosphere and thereby warming the planet and the ocean, Traps volcanism would have indirectly heated continental margin hydrate and released much of its methane.
