Alfred Wegener, looking around for some process in order to move the continents, thought drift was perhaps due to tidal forces from the Moon – and from the Sun. This was shelved and convection in the mantle replaced tidal forces as they were not thought to be strong enough. In fact, even in modern climate science, the role of tidal forces, particularly in respect of solar and planetary influences, is not thought to be strong enough to bother taking into account – and that is just the weather. According to Tall Bloke's reading of the Wikipedia page – see http://tallbloke.wordpress.com/2013/01/25/sir-harold-jeffreys-and-leif-s… … he is unsure if solar variability plays a role (but see also http://en.wikipedia.org/wiki/Plate_tectonics … ) which reminds us all that the debate over Plate Tectonics is not as fixed as its proponents would have you believe.
Some people do not think Plate Tectonics is taking place – others that it takes place in a manner differnet to that envisaged by the consensus. It is considered certain that sea floor spreading and subduction are happening but New Concepts in Global Tectonics have lots of papers arguing otherwise (www.ncgt.org). In the lead are Russian scientists, such as Belonssar. He is of the opinion that geophysical data, especially tomographic data of the Earth, is interpreted only in terms of temperature variations and not for other reasons. If science was being conducted properly both side of the debate would be tested, one against the other – but they aren't. A controversy exists regarding hypothetical mantle plumes which is all part of a much wider problem. Geophysicists and geochemists have no real clue on what is really happening in the mantle – it is all based on theory and modelling. Scientists don't all agree on how thick the crust is. Theoretical ideas are floated, unconstrained by actual and verifiable data. In issue 55 at www.ncgt.org/newsletter.php there is a paper by K Storedveldt. In the consensus theory the Earth's crust is split into plates and fault lines which are all lart of the concept of plate movement. In the alternative theories the plates and fault lines in the crust were caused by stress. According to Peter M James, an Australian geologist, polar wander or movement that occurs rapidly, or even less rapidly, is responsible for the stress that caused cracks in the crust – a completely different concept. In other words, the crust, having to come to terms with a displacement of the equatorial bulge, the oceans, and therefore what is above and what is below the global sea level, and the Poles (where there is ice and where there was ice) cracks and created fault lines. Looking at it from this angle both sides appear to have good points. The Plate Tectonics argument is still attractive as we have that jig saw like fit between one side of the Atlantic and the other. In Plate Tectonics theory the Atlantic began as a giant crack in the crust – what was a greater continental land mass. It came apart at the seams and has been growing apart ever since, slowly and inexorably. However, it is worth noting that if continents are not moving apart, or banging into each other, a mechanism for changing climate over millions of years has to be devised. At one time it was accepted that polar wander was to blame. In modern Plate Tectonics theory this is out of the question – only uniformitarian movement of the continents is allowed. Polar movement smacks of catastrophism. It is an unspoken mechanism in geological circles. Avoided. The beauty of catastrophism in this context is that it allows bits of both sides to share in the spoils. Instead of continuous and gradual movement involving a spreading ocean bottom the process becomes episodic – proceeding in jumps and bounds. A cracked crust can be part of the equation as well as rapid movement of continental crust.
It is interesting that it is Russian geologists who are most prominently against Plate Tectonics – but there is a reason. The theory was developed in the 1950s and 1960s, becoming dominant following the discovery of magnetic stripes on the ocean floor, and certain other factors, but this was during the Cold War. Russia was excluded. Isolated. Is this a blessing as the consensus is now embedded and the odd rogue scientist can be dismissed fairly easily – but a whole lot of scientists in Russia is a different picture altogether.
The Wikiepedia entry is far from complacent. It says, although subduction is believed to be the strongest force driving plate motion it cannot be the only force since there are plates such as the North American plate, which are moving yet are nowhere being subducted. The same is true for the enormous Euroasian plate. Okay – let's repeat that again. Sea floor is spreading on one side and as a counter balance crust is subducting somewhere else. In reality, deep sea trenches are believed to represent subduction regions but there are not enough of them. There is no subduction taking place as far as the Eurasian continent or the North American continent is concerned. Ocean trenches could be created by means other than subduction. In addition, the sources of plate motion are a matter of debate among scientists doing research, which implies, Plate Tectonics is not as done and dusted as they would have you believe. So, is there another driving force – apart from an expanding earth hypothesis?