The theory of plate tectonics states that the Earth's surface, the upper mantle and crust, was once made up of enormous rock plates that broke into smaller pieces approximately 300 million years ago. These smaller, broken plates form a more fluid rock surface in the mantle. Over time, the plates move and morph into natural land boundaries. This explains natural land phenomena, such as earthquakes and tsunamis.Continue Reading
In 1912, meteorologist Alfred Wegener proposed the first plate tectonics theory: all of the continents, at one time, were connected and formed a single super-continent called Pangaea. This explains why the coastlines of the continents appear to fit together like pieces of a puzzle.
During hundreds of millions of years, the plates have moved and changed position. Sometimes they move together, sometimes they separate and move apart and sometimes they move past each other. When the plates move past each other, they sometimes touch and make one plate rise up as the other slides down. That up-down movement causes an earthquake, which results in a land fault or crack. If the movement happens in a large body of water, it can create giant water waves called tsunamis. The major plates are known as North America, South America, Eurasia, Africa, Indo-Australian, Pacific and Antarctica.Learn more about Geology
Constructive plate boundaries are divergent zones where the Earth forms new crust through the cooling of lava. The Internet Geography website states that most of these boundaries occur under the ocean.Full Answer >
According to About.com, the Earth creates mountains through plate tectonics, where its crust is broken into plates constantly in motion, causing stress and uplifting in order to grow mountains. While growth is slow due to these forces, it does happen.Full Answer >
The plate tectonics theory suggests that the outer shell of the Earth's surface is split into a few plates that move along the mantle, forming a hard shell, with pressure from mid-ocean ridges and subduction zones causing the shifting in the plates. Mid-ocean ridges are the gaps that lie between the plates, much like the seams on a basketball. Magma oozes through these ridges, creating new crust on the ocean floor and pushing the plates apart, while subduction zones sit at the meeting point between plates. One slides under the other, pulling the crust down as it goes.Full Answer >
Andrew Alden of About explains that Australian geologist Sam Carey's theory of Earth expansion, the idea that the continents fit together properly only on a formerly smaller Earth, once rivaled the theory of plate tectonics. Carey's ideas expanded upon Wegener's continental-drift theory and hypothesised that the continents fit together properly on a shrunken Earth. From about the 1930s to the 1950s, this idea of Earth expansion remained a legitimate hypothesis.Full Answer >