Plate Tectonics is a theory that describes the movement of the seven largest plates of the Earth. The concept came into existence during the 1960s. The earth’s lithosphere is made up of different levels that differ from each other in physical and chemical properties. Apart from these, there are the continental and oceanic crusts. These make various landforms and are susceptible to various types of tectonic movements.
It was over the past hundred thousands of years, the tectonic plates have been moving leading to continental drift. So, the lithosphere comprises of seven to eight major and several minor plates. The meeting place of these plates decides the type of their boundaries. These can be of the following types: Convergent, Transformed or Divergent. These boundaries are the places where activities like Earthquakes, Volcanoes, Ocean trench formation and Mountain building happen. The divergent boundaries are when the two plates spread apart. On the other hand, convergent margins are the ones in which the plates come together and the Transform boundaries are the ones in which the plates slip and grind past each other horizontally.
The force that drives the plate tectonics is convection of the mantle. The hot material in the core called the Magma rises and the cold mantle rocks sink. This leads to a continued pushing and opening out at the Mid-ocean ridges and sinking down at the subduction zones. The Magma builds up in these ridges making the plates move even further apart and creating new oceanic crust.
The major plates are Antarctic, African, Eurasian, South American, Pacific, and Indo-Australian. The smaller plates are Caribbean, Cocos, Arabian, Philippine Sea, Nazca, Juan de Fuca, and Scotia. These plates are constantly moving even in the present times. The Pangea is the recent supercontinent that was formed about three hundred million years ago. In this supercontinent, the continents of Africa, North America, South America and Europe came close together. These add up to puzzle pieces in the today’s geography. These pieces drifted apart slowly and formed the world that we live in now.
Alaska is located somewhere in between the Pacific and the North American plates. Hence, it receives the most tectonic movements in the whole of United States. It has been seen through the past analysis that the Pacific plate moves about 5 to 7 cm in the North West direction every year. This leads the crust in Southern Alaska to get compressed leading to either upliftment or depression of the coastal areas. So, in essence, the Pacific plate gets pushed under the North American plates and this results in mountain building, ocean trenches, and volcanic activities.
The studies have also shown that from the Jurassic times, the block of Alaska consisting of the Alaskan Peninsula and Aleutian Range has approximately rotated 59° clockwise and its movement towards north has been approximately 19° of latitude.
Alaska is the most prominent region that has been facing earthquakes and tsunamis due to these tectonic movements. The mountains are growing in height day by day and this is the only reason that Alaska has so many rivers and varied landforms.