ImagingGeek,
The current theory, the Gravity Theory of Mass Extinction (GTME) is supported by not only the things just described, i.e., the extreme size of some dinosaurs, their near equatorial habitats per the theorized gravitational gradient and the disappearance of all non-avian dinosaurs near the K-T boundary, but by other evidence.
Courtillot makes the case for hot-spot volcanos as an alternative to the asteroid impact mode of extinction. He correctly points out the numerous extinction events that have occurred in the last 250my that were accompanied by hot-spot volcanos. These volcanos are believed to originate at the core/mantle boundary, producing a plume that rises to the Earth’s surface. As you know, the hot-spot volcano that formed the Deccan Traps in India was active during the K-T transition. The killing mechanism of both the hot-spot volcanos and asteroid impacts are believed to be similar: sulfur compounds ejected into the atmosphere causing a cooling of temperatures followed by a global warming from carbon dioxide, in addition to the effects of other contaminates injected into the atmosphere. However, no explanation for the cause of hot-spot volcanos is offered.
The GTME does offer an explanation for the hot-spot volcanos, which is that they result from movements of the core(s). And, of course, the core movements are the result of movement of large continental masses. Based on this, during the last 200my when Pangea rifted and broke apart, each significant movement of continental mass resulted in a pulse of two things: a plume of basaltic lava that would form a hot-spot volcano eruption and a pulse of surface gravity increase. Therefore, the coincidence of the extinction events and hot-spot volcanos are tied together and the extinction events, according to GTME, were the result of gravitational increases and not the result of cooling, global warming or other volcanic/asteroid causes.
The Deccan Traps produced a very large number of volcanic flows over a period of perhaps a million years (although the duration is debated). Therefore, the GTME posits that each flow corresponds to a major movement of continents. The continents, during this period, had separated from Pangea and were moving apart rapidly, primarily longitudinally. This movement would have resulted in major core shifting; moving the core(s) toward the central location while initiating the plumes. Since the K-T transition, the magnitude of hot-spot volcano’s flood basalt outpouring has steadily declined, something that would be expected because continental movement would have a corresponding lesser effect on core movement as the land masses moved further and further away from the consolidated Pangea position.
The common belief that an asteroid or even volcanism caused the K-T extinctions, based on the GTME, must challenged. It is not disputed that they can cause local extinctions but to be able to wipe out entire global species required a global force. I believe changes to surface gravitation was that force.
Laze
