Pakistan

Planet Earth appears to be big with an endless ocean of air around. Astronauts see the planet as small dot set against black background with a thin layer of atmosphere. Environmentalists fear that our home planet is slowly scorching. Earth is the third planet from the Sun at a distance of about 150 million kilometers. It takes 365.256 days for the Earth to travel around the Sun and 23.9345 hours for the Earth to complete one rotation. It has a diameter of 12,756 kilometers. Atmosphere is composed of 78 percent nitrogen, 21 percent oxygen and 1 percent other element. About 71 percent of earth’s surface is covered by water and the rest is land.

Earth is the only planet known to shelter life. Earth’s surface is surrounded by a layer of gases known as the atmosphere, which extends upward from the surface, slowly thinning out into space. Below the surface is a hot interior of rocky material and two core layers composed of the metals nickel and iron in solid and liquid form. Unlike the other planets, Earth has a unique set of characteristics suited to support life. It is neither too hot, like Mercury, the closest planet to the Sun, nor too cold, like distant Mars and the even more distant outer planets: Jupiter, Saturn, Uranus, Neptune, and tiny Pluto. Earth’s atmosphere distinguishes it from the planet Venus, which is otherwise much like Earth. Venus is about the same size and mass as Earth and is also neither too near nor too far from the Sun. But because Venus has too much heat trapping carbon dioxide in its atmosphere, therefore its surface is extremely hot for life to exist.

Life itself contributes to changes on Earth, especially living things can alter Earth’s atmosphere. For example, Earth at one time had the same amount of carbon dioxide in its atmosphere as Venus now has, but early forms of life helped remove this carbon dioxide over millions of years. These life forms also added oxygen to Earth’s atmosphere and made it possible for life to evolve on land. And now the gases produced by human activities are making changes.

As per the Earth science, our planet is one of the most active of all the planets in the solar system. Earth is constantly changing. Most of these changes have been gradual, taking place over millions of years. Nevertheless, these gradual changes have resulted in radical modifications, involving the formation, erosion, and re-formation of mountain ranges and the movement of continents.

The weathering and erosion that result from the water cycle are among the principal factors responsible for changes to Earth’s surface. Another principal factor is the movement of Earth’s continents and seafloors and the buildup of mountain ranges due to a phenomenon known as plate tectonics. Heat is the basis for all of these changes. Heat in Earth’s interior is believed to be responsible for continental movement, mountain building, and the creation of new seafloor in ocean basins. Heat from the Sun is responsible for the evaporation of ocean water and the resulting precipitation that causes weathering and erosion. In effect, heat in Earth’s interior helps build up Earth’s surface while heat from the Sun helps wear down the surface.

Knowing our mother planet better can make a difference. {X - Posted From Here}