The Earth’s crust has been in constant motion since its formation 4.6 billion years ago. Fractured into a patchwork of plates and floating on currents of molten rock beneath, the plates collide and pull apart.
In fact the floor beneath your feet, even though it feels stable and motionless, rests upon a land mass that is in continuous motion. The plates that form the Earth’s crust are 50-100 kilometers thick. It has long been suspected that the plates are in motion, but the mechanism that drives them remained a mystery for many years.
The east coast of South America and the west coast of Africa look as though they would fit together like the pieces of a jigsaw puzzle. With a bit of rearranging, most of the continents can be put together too. This was one of the first clues to continental drift, but other evidence supports the theory. Recently, the magnetic properties of rocks have been used to demonstrate the movement of continents. Lasers measure the movement across the San Andreas Fault in California, where two continental plates slide past each other. Measurements from satellites show North American and Europe to be drifting apart at the rate of about 4 centimetres a year.
Today we know that all the surface elements of planet Earth are in constant motion. To understand continental drift we have to understand how these elements, or plates, move. The study of the crustal plates and their movement is called Plate Tectonics.
Current form within any liquid when it is heated, just as they do in a pot of boiling soup. Similar currents form with the Earth’s thick, dense mantle. Radioactivity in the Earth’s core is a cause of the uneven heating of the lower mantle.
As the semi-molten rock of the mantle is heated, it rises, creating massive, slow convection currents within the Earth. The heated rock spreads laterally at the base of the solid lithosphere, dragging fragments of the Earth’s crust with it. As the Earth’s crust moves, volcanoes and earthquakes occur.
A powerful convection current pulls the Earth’s crust apart. Rift valleys form where continental plates separate. East Africa’s Great Rift Valleys, evidence of a continental pulling apart, is also a glimpse of an ocean in the making. When the rift is deep enough, it will be flooded by the sea.
The Gulf of Suez and the Gulf of Aqaba slowly advance into rifts that mark a fracturing continent. A gift extends from the Red Sea and splits at its northern end, signaling the eventual of Africa and the Middle East.