Plate Tectonic Theory

The earth’s crust is made up of seven major and several minor plates , which fit closely together. The positions of the plates are not static. They are constantly moving relative to one another.

The type of movement between plates affects the way in which they alter the structure of the earth.

Plate Tectonic Theory says The earth’s crust is splitting up into dozens of pieces called tectonic plates , which float on top of the mantle .Warmed by the blazing hot core, the mantle churns in circular convection currents , dragging tectonic plates along for the ride.

The movement of continents relative to each other across the Earth’s surface is known as continental drift. Although it was a subject of speculation by numerous early workers, the first comprehensive case of continental drift was presented by the German meteorologist, polar explorer, astronomer, and geologist, Alfred Wegner in 1914. Wegner suggested that all the Earth’s land had once been joined into a single supercontinent, surrounded by an ocean. He called the land mass Pangaea ( Pan=all + Gaea=earth ) and the surrounding ocean Panthalassa( Pan=all+ Thalassa=ocean). Wegner thought Pangea had broken into pieces during the Carboniferous period. Since then, the pieces had moved to their present positions and are still moving.

Some continents look exactly like puzzle pieces that snap together . Early map makers suspect once they were all connected. He thought different chunks of it moves apart, to form like continents we know today.

Wegner cited various evidence in support of his theory of super continent ( Pangea) which gradually seperated into Northern ( Laurasia ) and the Southern ( Gondwanaland ) landmass before finally splitting into continents of the present day.

Wegner’s evidence included the apparent shore fit of continents across the North and South Atlatic. The evidence included the matching configuration of opposing continental coastlines, the similarity of geological structures on seperate continental masses, the anomalous location of ancient deposits, indicating specific climatic conditions, and distribution of fossil species through time.

He believed that the continents were slung towards the equator on the spinning Earth by a centrifugal effect, while the westward movement of the continents was due to the tidal force of the Moon and the Sun. The theory was rejected first by most geologists and geophysicists, largely because of a lack of viable mechanism. Wegener was dismissed as a crank. His critiques claimed, with some justification, that he had carefully selected those evidence, supporting his hypothesis, ignoring contrary contrary evidence. Where, for instance, were the ‘wakes’ or ‘tracks’ through old seabed that the migrant continents would leave? But a few geologists sided with Wegner. Further support for continental drift was provided during the 1950s and 1960s through evidence from paleomagnetism. In 1967 the idea was incorporated into the theory of Plate Tectonics.

That large continent Pangea started 200 Million years ago. Split of Pangea and Panthalassa resulted the formation of continents as of today.

Wegner couldn’t explain why and how the continent Pangea splited. It is because similar plants and rocks found the parts which get drifted. Ages and types of rock layers matched upto.

Continental drift have influenced the evolution . One of the most prominent example of effect of continental drift on evolution of organisms was the unique primates found in Australia and South Africa.

Rejected at first , by the scientific community Wegner’s theory of continental drift eventually was proved correct.

Today plate techtonic is the unifying theory of of the entire fields of geology. It explains the rock cycle , the origin of Earth’s surface features , and the cause of seismic activity such as earthquakes and volcanoes.

When the earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide. When living organisms originated, they modified the early atmosphere of the earth.

From electromagnetic radiation to revolution of the earth everything is responsible for bringing dynamic changes on the surface of the earth and that changes made the earth as of the form we live now.

The early atmosphere largely contained water vapor, nitrogen, carbon dioxide, methane, ammonia and very little of free oxygen. The process through which the gases were outpoured from the interior is called degassing. Continuous volcanic eruptions contributed water vapor and gases.

The energy from earth, Geothermal energy is the heat received from the earth’s core, this heat continuously flows outwards. It transfers to the surrounding layers of the rock, the mantle. When temperature and pressure becomes very high some mantle rocks melt becoming magma.

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