Articles | Volume 6, issue 3
Solid Earth, 6, 1075–1085, 2015
Solid Earth, 6, 1075–1085, 2015

Research article 23 Sep 2015

Research article | 23 Sep 2015

Phase change in subducted lithosphere, impulse, and quantizing Earth surface deformations

C. O. Bowin1, W. Yi2, R. D. Rosson3, and S. T. Bolmer1 C. O. Bowin et al.
  • 1Woods Hole Oceanographic Institution, Woods Hole, MA, USA
  • 2Intelligenet Solutions Group, John Deere, Kaiserslautern, Germany
  • 3Applications Engineering Group, MathWorks, Natick, MA, USA

Abstract. The new paradigm of plate tectonics began in 1960 with Harry H. Hess's 1960 realization that new ocean floor was being created today and is not everywhere of Precambrian age as previously thought. In the following decades an unprecedented coming together of bathymetric, topographic, magnetic, gravity, seismicity, seismic profiling data occurred, all supporting and building upon the concept of plate tectonics. Most investigators accepted the premise that there was no net torque amongst the plates. Bowin (2010) demonstrated that plates accelerated and decelerated at rates 10−8 times smaller than plate velocities, and that globally angular momentum is conserved by plate tectonic motions, but few appeared to note its existence. Here we first summarize how we separate where different mass sources may lie within the Earth and how we can estimate their mass. The Earth's greatest mass anomalies arise from topography of the boundary between the metallic nickel–iron core and the silicate mantle that dominate the Earth's spherical harmonic degree 2 and 3 potential field coefficients, and overwhelm all other internal mass anomalies. The mass anomalies due to phase changes in olivine and pyroxene in subducted lithosphere are hidden within the spherical harmonic degree 4–10 packet, and are an order of magnitude smaller than those from the core–mantle boundary. Then we explore the geometry of the Emperor and Hawaiian seamount chains and the 60° bend between them that aids in documenting the slow acceleration during both the Pacific Plate's northward motion that formed the Emperor seamount chain and its westward motion that formed the Hawaiian seamount chain, but it decelerated at the time of the bend (46 Myr). Although the 60° change in direction of the Pacific Plate at of the bend, there appears to have been nary a pause in a passive spreading history for the North Atlantic Plate, for example. This, too, supports phase change being the single driver for plate tectonics and conservation of angular momentum. Since mountain building we now know results from changes in momentum, we have calculated an experimental deformation index value (1–1000) based on a world topographic grid at 5 arcmin spacing and displayed those results for viewing.

Short summary
This is a story about the ever-changing surface of our planet and how and why that happens. The first author was thanked by Hess (1960 preprint), but he only watched the theory’s growth from the sidelines. The 10 years that followed brought forth a deluge of evidence. Now 55 years later, no net torque amongst the plates remains, but still without a mechanism. Bowin (2010) demonstrated plate tectonics conserves angular momentum, but few appear to note its existence. This clarifies the mechanism.