Continentale drift

As far as I understand it, the continents ARE just floating on the Earths crust. Sorry to destabilise you! I'm not entirely sure how this works as the surface of the earth is mainly granite and the substance it 'floats' through is basalt. There is another theory that it is not that the continents drift but that they are pushed apart. The surface layer is thinnest on ocean beds and it has been suggested that molten mantle may well up along fracture lines of ocean beds and its hardening pushes the continents apart. I read this in Asimovs New Guide to science published in 1984 so the theory has probably been either accepted or discredited by now. Continental drift can only occur along fault lines as the basalt does hold everything together pretty well other than at these weak points and I would infer from this that, as fault lines are known for their volcanic activity and earthquakes that the eruptions occur not in the wake of drift but preceding it and causing it. Once the volcanic lava hardens it forces the fault line apart. I think that sea levels were different at the time of Pangea for the same reason. Fault lines run under the sea and, as I said this is where the crust is thinnest so there is a greater incidence of volcanic activity below the sea than above. I just looked it up as I had a feeling I had read something about the 'newness' of the ocean floor and apparently, sediment from the ocean floor is rarely found to be older than 100 million years old (the planet having been around more than 45 times as long). The magma that erupts forms new surface and so raises the sea level. Additionally, and I can't claim to fully understand how this works myself, the seperated continents develop seas in the gap and this causes something called 'sea-floor spreading' which also affects the sea level. Where continents drift and meet, the crust breaks up and bulges up and down to form mountain ranges but this only occurs when the drift and eventual meeting is fairly slow. If the plates hit too rapidly, one plate will force itself under another forming a deep trench and these lines in particular have a tendency towards volcanic activity. The reason the planet doesn't fall apart is because there is no widening of land mass as such. The process recurs over and over. Two plates come together but then are later pushed apart again where they float off and bash into another continent. Hope that helps a bit.

So my understanding of the process of tectonics is thus. The earth is spinning on an axis which gives us gravity. This gravity keeps the earth in its shape and keeps all of the mass confined to the space it inhabits. The Asthenosphere which is the liquid layer that lies beneath the outer crust is a hot, weak, flexible layer that can average 10-300km deep. This is the layer where the fuel for volcanoes, the replenishing of the sea floor comes from, and where the crust is destroyed adding to the fuel to replenish. As the continents move, there are 4 different types plate motions. Divergent boundries where new crust is created as the plates move away from eachother Convergent boundries where crust is destroyed as one plate moves below another Transform boundries where crust is neither created or destroyed due to the plates sliding horizontally against eachother. I am of the mind that the moon has a part to play in the continent drift, considering the substanial effect it has on our oceans. As for things not just falling apart, the plates are all touching eachother in some fashion which helps create pressure and keep things together like a jigsaw puzzle.

i cannot explain it to you, but i understand the procedure, it is just about geology and a little phisics.