Hawaii, Tombstone of the Dinosaurs, Part 2: The Bend in the HEC

The bend in the Hawaiian-Emperor Chain has recently been attributed to a 1500km motion of the Hawaiian hotpot from a more polar latitude to its present position during times more ancient than 43 Ma. Such motion is explained if one assumes that the hotspot is the result of an iron asteroid that embedded in Earth's upper mantle and gravitated to the CMB along a path determined by the gravitational effects of Earth's equatorial bulge. The heuristic value of this idea is large because it provides a single explanation for the following observations: 1. Why there is a bend in the HEC. The mass of Earth's equatorial bulge would have caused the impactor to gravitate toward an axial point south of Earth's center. The gravitational effect of the bulge is maximal at 45N latitude and the recent studies indicate that the impactor hit ocean slightly north of 39.7N. Friction associated with the asteroid's downward and southward motion would have produced a rising train of mantle materials (the Emperor portion of the HEC). The bend occurred when the asteroidal mass reached the core-mantle boundary. The asteroidal mass now resides on the mantle side of the CMB. It continues, however, to slowly move toward a more equatorial position as a consequence of Earth's equatorial bulge, this being the reason that the seamounts of the Hawaiian chain are slightly angled relative to the WNW direction of motion of the Pacific plate. 2. Why the magma generated by the Hawaiian hotspot is siderophile-enriched relative to Pacific rim volcanos. The iron impactor was not extensively dispersed throughout the mantle or atmosphere following its collision with Earth. Throughout its downward migration through the mantle (and presently at the CMB) frictional heating associated with its motions produced the magma of the HEC volcanoes, which includes material eroded from the impactor. 3. Why the Hawaiian hotspot has continued to function as a significant heat source for the past 43 Ma. Differential rotation of the core vis-…-vis the mantle causes the asteroidal mass to tumble at the core-mantle boundary. Rotational deformation and electromagnetic coupling between Earth's main magnetic field and the impactor-iron generates excess heat at this location. 4. Why the Sr87/86 ratios increase in going from Suiko to the bend and remain constant thereafter. The strontium ratios reflect the motions of the asteroid's downward movement through the mantle and its fixed depth since the bend. 5. Why there is a circular ring of mountains (Rockies, Central America, Andes, trans-Antarctic, Australian Rise, Indonesia and Philippine Islands, East Asian Rise, the Kolymas, Japanese Islands, Brooks, Mackenzie's) that were centered on the Hawaiian impact site circa 65 Ma. The primary shock front associated with the original impact would have been reflected away from the impact site by the curvature of the Earth's core. As a consequence, the impactor's main mass is not extensively disrupted by rebound effects that would otherwise cause its dissolution. While the position of the circular ring of mountains is determined by the geometry of the core-reflected shock front punching up from beneath the continental plates, the greater portion of the orogenic energy is attributed to the impact-catalyzed release of stress-coupled stored tectonic energy (due to plate motions occurring prior to the impact). See: Hawaii: Tombstone of the Dinosaurs, RD Brown, Eos 75: 418 (1994) 6. This model explains why the greatest terrain and faunal damage at the KT boundary occurred in the western portions of NA and the eastern portions of Asia, a distribution not explained by the Yucatan impact. Twinning of asteroids is common.