Plate Tectonics Not The Only Answer
Most people with an interest in science are familiar with the story of how, back in 1912, Alfred Wegener proposed the theory of continental drift to explain the striking way that continental margins seem to fit together like jigsaw puzzle pieces. But he met rejection until the accumulation of supporting data led to in general acceptance of the idea over 40 years later in the form of plate tectonics. However, it appears that this in turn is now coming in for its share of doubts and questioning from various directions. The most commonly leveled criticisms are that the subduction of crustal plates down into the mantle held to be taking place along the west Pacific trench system to compensate for the appearance of new crust elsewhere at the ocean ridges isn't supported by any hard evidence--and it's questioned whether the subduction of light continental granite beneath the heavier underlying basalts is even physically plausible. Yes, there are deep-lying seismic signals, but the critics argue that this doesn't prove subduction as the cause; and the enormous amounts of sedimentary deposits that ought to be scraped off the top of the down-going plate at the edges of the trenches don't appear to be there. And despite the many theories that have been advanced, no satisfactory mechanism has been identified for causing the plates to move.
The underlying assumption for requiring crust to be consumed at the same rate that it's being created is, of course, that the size of the Earth has remained constant. But what are the grounds for making such an assumption in the first place? Indeed, if one goes with the current mainstream model of planet formation by accretion from a primordial nebula, then obviously such an assumption is invalid, since the Earth has grown over time. An interesting alternative view that seems to be attracting a growing number of proponents is that the Earth has continued expanding into recent times, and is in fact still doing so,and the fit of the continental margins shows how they once lay together on a smaller surface, before being ruptured by expansion-induced fissures that grew to become the oceans. In this model, the deep-seated seismic activity results from pieces of crust that were formed on a smaller sphere flattening out as they accommodate to a curvature of larger radius (like a piece of orange peel being pressed down on the surface of a basket ball). Advocates of the theory maintain that a smaller Earth gives a better continental fit than any reconstruction based on the size of the present-day Earth.
Proposals as to the reason for the expansion include (1) Continuing accretion of extra-terrestrial material from such sources as meteorites and larger objects, infall of dust, and continuous matter flow via the solar proton wind. (2) Matter-creation physics in action at the Earth's core. (3) Constant mass, but expansion of volume due to liquified material from deep down solidifying at the surface in a lower-density state.
A site with lots of information and many links is http://oilismastery.blogspot.com/2008/10/expanding-earth-outline.html The "oilismastery" part of the url refers to a section on the related topic of abiogenic hydrocarbons, which I touched on in an earlier posting The site also discusses the implications of changing of surface gravity, including the mystery, also mentioned previously, of impossible dinosaurs.