The present continent positions are not the same as their ancient positions. For example, Africa and South America used to be together in the old Gondwanaland. Alfred Wegener noticed the correlation in complementary forms of the coast lines of these two continents and developed the theory of continental drift. But it wasn't until the late 1960's or early 1970's that the mechanism for this movement was discovered in the theory of plate tectonics. Actually, it was shown that the mid-oceanic ridges like the one going through Iceland is where molten rock is welling up from the mantle on a zone of fracturing and the convection currents from this cause the ocean spreading and thus the movement of continents away from each other as in the case of Africa and South America.
Human activity can affect the amount of carbon in the atmosphere. When fossil fuels like oil, coal, and natural gas are burned, carbon dioxide is released into the atmosphere as waste.
When have the intentions to analyze the sea floor an try to measure the difference of materials present on the seafloor we woulds see or analyze that if we are moving away from the land outwards into the deep down ocean then we would see the sequence of the in the following way continental shelf - continental slope - abyssal plain.
