The oldest regions of continents, made of material that has been piling up for billions of years, have been “cooked” by heat and pressure and are made of crystalline metamorphic rocks. At the base of the crust is a boundary that reflects seismic waves, called the Mohorovicic discontinuity, or Moho. Beneath it are the rocky slabs of lithospheres mantle, composed mostly of iron and magnesium rich peridotite, on which the cruse floats. The more the weight laden on the crust, the lower it sinks. Mountainous areas have “roots” within the mantle which are significantly greater than the height of the mountains above. The balance maintained is called Isostasy.
It is possible to trace the history of the movements of continents’ waltzes around the globe over hundreds of millions of years. Their edges fit together like the pieces of a jigsaw; the similarities between their fossils and rock strata, the past climates they experienced and the orientation of magnetic minerals, frozen in volcanic rocks like tiny compass needles, all record their travels. Precise laser measurements taken from satellites reveal the present rate of continental drift. It is roughly comparable to the rate at which finger nails grow- a mere 4 to 5 Cm in a year across the Atlantic, 12 to 14 Cm in a year across parts of the Pacific