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BRIEF HISTORY OF CONTINENTS

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CONTINENTAL AREAS

ASIA: 17,208,000 SQUARE MILES

AFRICA: 11,608,000 SQUARE MILES

NORTH AMERICA: 9,449,000 SQUARE MILES

SOUTH AMERICA: 6,880,000 SQUARE MILES

ANTARCTICA: 5,100,000 SQUARE MILES

EUROPE: 3,841,000 SQUARE MILES

AUSTRALIA: 2,970,000 SQUARE MILES

    Out of the total earth area, around one-third is land, and balance two-third is water–ocean. Yet, the major land divisions—the continents—are the ones that give shape and physical identity to the planet.

    The seven continents represent some 57 million square miles in area, portioned unequally among them. They range in size from Asia, being the largest, to Australia, being the smallest. Although Europe and Asia form one large mass, they are usually regarded as two continents, mainly due to the cultural differences between their peoples.

    The seven continents as they appear today represent just one episode in an ongoing scenario of the wandering land masses. It is a process whose history dates back to the initial formation of continental material on Earth’s crust almost four billion years ago—a process called ‘plate tectonics.’

    The crust and the top portion of the mantle form a rigid shell around the planet that is broken up into 16 large sections known as plates. Heat generated inside Earth is distributed through convection current which causes the plates to move slowly. This sort of movement has been going on for hundreds of millions of years.

    Most geologists believe that the ‘continents’ were created when vast plates of rock collided, forcing one to slide under another in a process called ‘subduction.’ The crust then melted and formed magma, or molten rock. Erupting to the surface, the magma built volcanic islands that eventually fused with other islands on adjoining plates—becoming the first continental material.

HOW WERE CONTINENTS FORMED

    As Earth’s continental masses grew bigger, moving all the while, they shifted in relation with each other and coalesced into different arrangements over hundreds of millions of years. The current configuration of continents is just a temporary one in the eons-long process of the plate tectonics.

    Three times during the past billion years, drifting landmasses have merged to form supercontinents.

    In between these stages of continental drift, they split into smaller landmasses before recombining again. Scientists predict that a new supercontinent, ‘Pangaea Ultima,’ will eventually form, 250 million years from now.

TERMINOLOGY 

CONTINENT: Comes from the Latin continens, “held together.” One of Earth’s seven large masses of land.

TECTONICS: Comes from the Greek tekton, “builder.” Study of the changes in Earth’s crust and the forces that produce such changes.

SUBDUCTION ZONE: The oceanic trench area in which the seafloor ‘underthrusts’ an adjacent plate, dragging, accumulated sediments, downward into Earth’s upper mantle.

ALFRED WEGENER THE EARTH SCIENTIST

    German Earth Scientist Alfred Wegener (1880-1930), was among the first to use balloons to track air currents. He participated in expeditions to Greenland to study polar air circulation but became better known for his theory of continental drift. People had already noticed that the coastlines of western Africa and eastern South America seemed to match, but Wegener found evidence that the continents had been joined: because of similar fossils from both sides of the Atlantic and tropical species in Arctic areas. He posited the existence of a supercontinent, Pangaea (All Lands) that eventually broke up, and he presented his ideas in the Origin of Continents and Oceans—but few believed him. In the 1950s and 1960s, studies of the ocean floor demonstrated a mechanism for crustal movement, is when Wegener’s theory of continental drift gained acceptance.

BRIEF HISTORY OF EARTH

500 MILLION YEARS ago, a chunk broke off a single continent. Shallow waters spawned the first multicellular creatures.

300 MILLION YEARS ago, some of today’s mountains formed. A new ice age covered Earth’s southern regions.

225 MILLION YEARS AGO, the earliest dinosaurs roamed a single continent that stretched from Pole to Pole.

100 MILLION YEARS ago, cracks across the one continent, known as Pangaea, formed rifts that evolved into oceans.

50 MILLION YEARS ago, a climate changing meteor crashed into Earth and the highest mountains began their uprise.

20,000 YEARS ago, ice sheets a mile deep gouged out the Great Lakes and then receded, raising sea levels.

Posted by Kamlesh Tripathi

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