The division is based on differences in mechanical properties and in the method for the transfer of heat.
Intro to Plate Tectonic Theory Plate tectonics is the theory that Earth's outer layer is made up of plates, which have moved throughout Earth's history.
The theory explains the how and why behind mountains, volcanoes, and earthquakes, as well as how, long ago, similar animals could have lived at the same time on what are now widely separated continents. You probably wouldn't recognize the Earth if you could see it million years ago.
Back then, all the major continents formed one giant supercontinent, called Pangaea.
Perhaps initiated by heat building up underneath the vast continent, Pangaea began to rift, or split apart, around million years ago. Oceans filled the areas between these new sub-continents.
The land masses continued to move apart, riding on separate plates, until they reached the positions they currently occupy. These continents are still on the move today. Exactly what drives plate tectonics is not known. One theory is that convection within the Earth's mantle pushes the plates, in much the same way that air heated by your body rises upward and is deflected sideways when it reaches the ceiling.
Another theory is that gravity is pulling the older, colder, and thus heavier ocean floor with more force than the newer, lighter seafloor. Whatever drives the movement, plate tectonic activity takes place at four types of boundaries:Plate tectonics is the unifying theory of geology, said Nicholas van der Elst, a seismologist at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York.
Plate Tectonics Loading. Surface relief of the Earth #1: Image from computerized digital images and associated databases available from the National Geophysical Data Center, National Oceanic. Plate tectonics - Development of tectonic theory: The outlines of the continents flanking the Atlantic Ocean are so similar that their correspondence was apparent as soon as accurate maps became available.
The earliest references to this similarity were made in by Flemish cartographer Abraham Ortelius and later in by the English philosopher Francis Bacon, in his book Novum Organum.
Theory of Plate Tectonics. When the concept of seafloor spreading came along, scientists recognized that it was the mechanism to explain how continents could move around Earth’s surface.
Like the scientists before us, we will now merge the ideas of continental drift and seafloor spreading into the theory of plate tectonics. Ordering Instructions This book was originally published in paper form in February (design and coordination by Martha Kiger; illustrations and production by Jane Russell).