In the vastness of outer space lies a galaxy, known as the Milky Way. Inside this galaxy is our solar system- a bright star orbited by eight planets. The third planet from the sun is a unique planet called the earth. For us human, the earth seems huge and enormous, but in the vastness of space it is only a tiny speck.
As an inhabitant here on Earth, we all know that Earth is such a unique planet for life exists on this place. Earth is a rocky planet and is more than a million times smaller than the Sun. Unlike the other planets in the solar system, Earth has water and an atmosphere that contains oxygen which makes it support life. The atmosphere is made up of several layers and reaches hundreds of kilometers into space. The troposphere is the lowest layer containing enough air for plants and animals to breathe. The air in the stratosphere is much thinner and contains a thin layer of ‘ozone’. The outer layers in the atmosphere are the mesosphere, the ionosphere and the exosphere.
It takes 365.25 days for Earth to complete its orbit around the Sun. Earth spins on an axis that runs from the North Pole to the South Pole. It takes 24 hours for Earth to spin right round on its axis. Earth formed at the same time as the sun and the other planets of our Solar System. By studying rocks and fossils, scientists have estimated that the Earth existed 4.6 billion years ago.
For thousands of years, it was a common belief that Earth was flat. After all, it appears flat to the naked eye. But in 1522, Spanish explorer Ferdinand Magellan’s ship Victoria completed a historic journey- it sailed all the way around the world. This proved once and for all that Earth was round.
It is about 6,400 kilometers from the surface of the Earth to its center. Earth is made up of different layers of rock and metal. There are three main zones- crust, the mantle and the core. The crust is the outer layer of the Earth and is divided into two parts-continental crust and oceanic crust. The mantle which lies beneath the crust is made up of molten rock and is about 2,800 kilometers thick. The core of Earth consists mainly of the metals nickel and iron. It is hot and dense and is divided into two areas- a liquid outer core and a solid inner core.
From space, Earth looks spherical. However, it is not perfectly round. In fact, it is slightly flatter at the top and bottom- the Poles- and it bulges slightly at the middle around the equator.
We call earth as a blue planet. This is because 71 percent of the surface of the planet is covered by water. About 97 percent of the planet’s water is in the sea and is salty. The remaining water is in the rivers, lakes and glaciers. There are five oceans- the Pacific, Atlantic, Indian, Arctic, and Antarctic. The Pacific is the largest and deepest ocean.
Earth’s crust is divided into sections called ‘plates’ that are moved about by the mantle over millions of years. Continental crust- crust that makes up Earth’s land-30 to 40 kilometers thick. There are seven continents- North America, South America, Africa, Asia, Europe, Antarctica and Australia. Europe, attached to Asia is the smallest continent and it is argued that it is really part of Asia.
On the earth’s crust we can also see mountains and volcanoes. The world’s highest peak is the Mount Everest in Himalayas. The smallest volcano is the Taal Volcano in Philippines.
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| Mount Everest |
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| Taal Volcano |
