A continent is “a large one piece area of land on Earth”. All continents together constitute less than one-third of the earth’s surface. A continent is made up of many countries. Most of the continents are located in the Northern Hemisphere.
Continents Area (sq.km) Countries
Asia 44,579,000 47
Africa 30,065,000 57
North America 24,256,000 23
South America 17,819,000 12
Antarctica 14,000,000 0
Europe 9,938,000 50
Australia 7,687,000 3
Earth’s Tectonic Plates
The planet earth was very hot when it was formed 4.57 billions of years ago. As the temperature dropped gradually in the first few millions of years or so, its thinnest outer surface (rocky crust) cooled down first, solidified and broke up into huge thick plates called tectonic plates and each tectonic plate moved with the lower molten portion of mantle.
There are about eight major tectonic plates that drift horizontally in a slow manner, a few mm every year. The huge plate’s thickness is from 100 km to 400 km.
These plates move in different directions, changing their place in millions of years’ time, resulting in a change in the Map of the Earth. The surface of the Earth looked very different in the distant past 800 million years from its present appearance and will look different from now.
It is the movement of the earth’s tectonic plates that causes major geological phenomena including earthquakes, volcanoes, mountainous range and trench formation etc.
Types of tectonic plates:
There are two types of plates, Continental Plates and Oceanic Plates. Continental plates lie under the continents and oceanic plates lie under the ocean and are denser than continental plates. Continental plates consist of earth crust plus some portion of mantle. The plates move on the molten portion of the mantle about 700 km deep in the earth.
The place where the two plates meet is called a Plate boundary. Most of the Earth’s seismic activity occurs at the plate boundaries as they interact.
When the two continental plates collide with each other, Fold Mountains form. When oceanic and continental plates meet each other, the oceanic plate slides down or subducts beneath the continental plate as it is denser and as a result mountain forms.This phenomenon is called Subduction. The volcanic eruption also takes place.
When the two oceanic plates separate from each other, it causes volcanoes and islands in the ocean and the phenomenon is called Seafloor Spreading.
When two continental plates move sideways against each other, a tremendous friction and jerky situation is developed which results in earthquakes.
Zia Ahmed Khan email: khanziaahmed50@gmail.com
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