Plate tectonics is a theory suggesting that the outside edge or the crust of the Earth is a jigsaw of moving plates. It is the process responsible for continental drift and the changing position of the landmasses compared to today. It is linked to the science of Isostasy that consists in studying the general equilibrium in the earth's crust, that supposed to be maintained by the flow of rock material beneath the surface under gravitative stress.

" Have we not made the earth as a wide expanse,
and the mountains as pegs."<Qur'an-Nabaa 78:6-7>

" He created the heavens without any pillars that ye can see, He set on the earth mountains standing firm, lest it should shake with you..."
<Qur'an-Luqman 31:10>

Scientists confirm that mountains have below them roots that extend deep into the earth's surface and stabilize the earth's crust. The history of science tells us that the theory of mountains, having deep roots and being stabilizers for the earth, has just begun to be understood in the framework of plate tectonics since the late 1960’s. These roots can reach several times their elevations above the surface of the ground. So the most suitable word to describe mountains on the basis of this information is the word "peg", like the Qur'an describes it.

Mountains also play an important role in stabilizing the crust of the earth. They hinder the shaking of the earth. Likewise, the modern theory of plate tectonics holds that mountains work as stabilizers for the earth.

Could anyone imagine that the solid massive mountain which he sees before him actually extends deep into the earth and has a root, as scientists assert? A large number of books of geology, when discussing mountains, only describe that part which is above the surface of the earth. This is because these books were not written by specialists in geology. However, modern geology has confirmed the truth of the above Qur'anic verses.
Source : Professor Emeritus Frank Press, Science Advisor to former US President Jimmy Carter

Source :Earth Science, Tarbuck and Lutgens

In 1915, Alfred Wegener published the first edition of "The Origin of Continents and Oceans," in which he laid out his continental drift hypothesis and the evidence that he had amassed to support it. Wegener proposed that continents were not only capable of moving across ocean basins, but they had in fact done so, merging to form the supercontinent of Pangea (Greek for "all land") approximately 250 million years ago. The continents originally consisted of a single great land mass surrounded by one ocean. Pangea subsequently broke apart and the continents slowy made their way to their present positions. Wegener presented arguments based on geodesy, geophysics, geological relationships, paleontology and climate. The most often cited is the match of the coastlines of Africa and South America, Europe and North America. Reconstruction of these continents also explained the unusual distribution of terrestrial fossils,organisms which otherwise would have had to cross thousands of miles of open ocean, or else rely on hypothetical "land bridges" that some scientists envisioned spanning the Atlantic Ocean.

Pangaea of Wegener

250 million years ago... The world today...

It was known that lands now far apart and with very different climates contained the same kinds of fossil plants and animals. For example, certain dinosaur fossils have been found across central South America and western central Africa, and nowhere else. Identical fossil plants have been found in southern South America, southern Africa, India, Antarctica, and Australia. Evidence of an ancient glacier that was once one large ice cap can be found in South America, Africa, India, and Australia.

Many scientists rejected the continental drift theory because no one could explain what forces might move continents. Then in the early 1960's, a theory called sea-floor spreading provided some explanation. According to the theory, the sea floor itself moves, carrying the continents along. Circulating movements deep within the earth's mantle, that is, the thick layer of hot melted rock beneath the earth's crust, make the sea floor move. The circulating movements carry melted rock up to the mid-ocean ridges and force it into the central valleys of the ridges. As the melted rock cools and hardens, it forms new sea floor and pushes the old floor and the continents away from the ridges.

As mentioned above, the earth's outer shell consists of huge rigid plates that move continuously. As the plates move, they carry the ocean floor and the continents with them. The relative movement of two neighboring plates is generally about 1/2 to 4 inches (1 to 10 centimeters) a year. Different movements of the plates have different effects on the ocean bottom and the continents. Sea floor spreading, and the formation of new sea floor, occurs where plates move apart. The mid-ocean ridges mark such areas.

As plates move away from one another in one place, they must move toward one another elsewhere. When two plates collide, one plate may pile up against the other, forming mountains. Or one plate may be drawn down into the mantle under the other plate. Such action produces trenches and volcanoes. Earthquakes occur at or near plate boundaries, where the plates spread apart, collide, or slide past one another. The Atlantic Ocean is slowly growing wider and the Pacific smaller because of plate tectonics.