Why Isn't the Pacific Plate Showing its Age?

Elsewhere in the world's oceans, seafloor of Cretaceous age and older is really deep or already dead (subducted). In addition to having old, but apparently youthful (shallow) seafloor, the Pacific Ocean is the world's largest, and it contains the most hotspot activity, the fastest spreading ridges, and the most asymmetrically distributed ridge system. Are these properties in some way related? If so, which are the dependent and which are the independent variables? One can imagine scenarios linking at least two or more of these properties. For example, the large size of the plate puts cold mantle features, such as subducting slabs and old continental roots, far from the plate's center, perhaps facilitating upwelling associated with hotspots and reducing resistance to plate motion over the mantle. The hotspots may alter the density structure of the lithosphere, through crustal thickening, reheating, and/or mantle depletion, perhaps making older seafloor more buoyant and resistant to subduction. Any asymmetry in the distribution of seafloor altered by the hotspots could eventually lead to an asymmetry in basin widths on opposing sides of the ridge due to the resistance to subduction of the hotspot lithosphere. Unfortunately, there is little hard evidence that can be used to take such speculations beyond cartoons or back-of-the-envelope calculations. Earth only has a few plates, and our solar system only one example of plate tectonics, making it impossible to compare the fate of the Pacific with that of another plate similar with the exception of one of the independent variables. Computer models are useful, but differing assumptions of the initial conditions can lead to vastly different outcomes. Some hypotheses for how the Pacific plate ages could be ruled out by seismically imaging the crust and upper mantle along a flow line from the EPR to a subduction zone, crossing one or more hotspot chains along the way. Such an experiment could be accomplished using an array of portable seismometers taking advantage of the excellent azimuthal coverage of earthquake sources. The seismic images would need to be combined with geoid data in order to convert seismic velocity to density.