Rona & Richardson (1978)
present evidence that supports the hypothesis of Anderson
(2002). This hypothesis suggests that fluctuations in
stress in the lithosphere are responsible for global
plate reorganizations and evolution of volcanic chains.
Rona & Richardson (1978) present compelling
evidence for forced feedback from the plates to mantle
convection cells. The E-W length of N-S converging continent-continent
collisional plate boundaries increased from 2,500 to
28,000 km during the interval 55 - 40 Ma, and remains
at about 19,000 km. We infer that this increase in length
of collisional boundaries produced resistance to continued
N-S convergence and forced reorientation of plate motions.
Large N-S components of most resistance to motion, and
large E-W components of least resistance, became the
dominant pattern. Our evidence for a change to a dominant
E-W component of motion comprises continuation of pre-exsiting
E-W spreading, initiation of new E-W seafloor spreading,
an increase in length of subduction zones along convergent
plate boundaries to accommodate the spreading, deceleration
of spreading rates, and obduction of ophiolites as a
product of plate reorganization.
Global plate organizations have probably
occurred throughout most of geologic history. The Eocene
reorganization is exceptional in that nearly the entire
record is preserved in magnetic lineations, hot spot
trends (including the Emperor Seamount-Hawaiian Ridge
bend), collisional mountain belts, and ophiolites. For
this reason, the Eocene reorganization provides clear
evidence of how the plate system actually works.
Anderson, D.L., Plate tectonics
as a far-from-equilibrium self-organized system.
in S. Stein and J.T. Freymueller, Editors, Plate
Boundary Zones, Am. Geophys. Un., Geodynamics
Series, v. 30: 411-425, 2002.
Rona, P.A., and E.S. Richardson,
Early Cenozoic global plate reorganization, Earth
Planet. Sci. Letters, 40: 1-11, 1978.
Peter A. Rona, Ph.D., Professor of Marine Geology and
Institute of Marine and Coastal Sciences
71 Dudley Road
New Brunswick, New Jersey 08901-8521
Phone: 732/932-6555 x 241