No. 128: MAR-APR 2000
65-million years ago. This was the time of the well-publicized, but still hypothetical, asteroid impact. It is said to have wreaked havoc on our wounded planet and, especially, the dinosaurs. Volcanos spewed out vast lava fields and filled the air with greenhouse gases and dust. It was a bad time for many life forms.
Actually, It may have been far worse than generally advertised. In addition to the volcanic activity and climate change, the shock of the asteroid impact could have been sufficient to destabilize the immense amounts of methane hydrate that have long been locked up, frozen and dormant, in oceanic sediments all over the world.
According to this scenario, once the shock of the asteroid impact released the methane from its icy prison, it rose to the surface of the oceans in a world-wide burp. Methane, unfortunately for the dinosaurs and many other life forms, is highly flammable. Lightning could have ignited it almost immediately if it was concentrated enough. A colossal firestorm might have then enveloped the entire planet. The whole atmosphere could have been afire. This, according to B. Hurdle and colleagues at the Naval Research Laboratory, who speculate that the dinosaur hegemony may ended suddenly in flames rather than in a long, drawn-out whimper.
(Day, Michael; "Hell on Earth," New Scientist, p. 5, November 20, 1999)
55 million years ago. Ten million years after the dinosaurs may have roasted in a global firestorm, another methane burp may have erupted from the oceans. This burp was slower and did not ignite but was just as lethal. It filled with atmosphere with a highly effective green-house: methane. The result was a pulse of global warming; as seen in a 5-7-deg C increase in the temperature of ocean-bottom water during that period.
Biological evidence for the event occurs in the skeletons of marine animals that litter the ocean sediments laid down in that lethal period. On the land, prior to the methane release, North America was'populated by an odd assortment of unfamiliar mammals; "unfamiliar" to ustoday because they left no descendents. These archaic mammals succumbed to the effects of the sudden global warming and were ultimately replaced by the ancestors of our familiar deer, horses, and canines that streamed across the now-open Bering Land Bridge.
Geology, too, provides evidence of this traumatic event. Ocean-bottom cores reveal landslide debris that was probably triggered by the sudden decomposition of great masses of methane hydrate. Seismic probes of the ocean sediments reveal chaotic zones suggesting a violent event.
(Kerr, Richard A.; "A Smoking Gun for an Ancient Methane Discharge," Science, 286:1465, 1999. Monastersky, R.; "Global Burp Gassed Ancient Earth," Science News, 156:260, 1999.)
Philosophical observation. Just as natural fires of grasslands and forests eventually lead to vigorous new growth, it appears that methane (a natural product of the decomposition of organic material) also sweeps out old species and replaces them with new ones. No doubt this planetary cleansing is another ramification of the Gaia Hypothesis.
Be advised that Gala still lives, and that huge, unstable, methane-hydrate deposits still lie buried under many continental shelves.
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