The Planet Earth

Introduction of Planet Earth• Earth is the third planet from the Sun, the densest planet in the Solar System, the largest of the Solar System's four terrestrial planets, and the only astronomical object known to harbor life.

Land• Land, sometimes referred to as

dry land, is the solid surface of the Earth that is not permanently covered by water. The vast majority of human activity occurs in land areas that support agriculture, habitat, and various natural resources.

The seven continents• Africa• Antarctica• Asia• Europe• North America• Oceania

AfricaAfrica is the world's second-largest and second-most-populous continent. At about 30.2 million km2 (11.7 million sq mi) including adjacent islands, it covers six percent of Earth's total surface area and 20.4 percent of its total land area.[2] With 1.1 billion people as of 2013, it accounts for about 15% of the world's human population.[1]

 The continent is surrounded by the Mediterranean Sea to the north, both the Suez Canal and the Red Sea along the Sinai Peninsula to the northeast, the Indian Ocean to the southeast, and the Atlantic Ocean to the west. The continent includes Madagascar and various archipelagos. It has 54 fully recognized sovereign states(or countries), nine territories and two de facto independent states with limited or no recognition.

Antarctica Antarctica is Earth's southernmost continent, containing the geographic South Pole. It is situated in the Antarctic region of the Southern Hemisphere, almost entirely south of the Antarctic Circle, and is surrounded by the Southern Ocean. At 14,000,000 square kilometres (5,400,000 square miles), it is the fifth-largest continent in area after Asia, Africa, North America, and South America. For comparison, Antarctica is nearly twice the size of Australia. About 98% of Antarctica is covered by ice that averages 1.9 kilometres (1.2 mi) in thickness,[6] which extends to all but the northernmost reaches of the Antarctic Peninsula.

AsiaAsia is the Earth's largest and most populous continent, located primarily in the eastern and northern hemispheres. Asia covers an area of 44,579,000 square kilo meters, about 30% of Earth's total land area and 8.7% of the Earth's total surface area. It has historically been home to the world's first modern civilizations and has always hosted the bulk of the planet's human population.[3]

 Asia is notable for not only overall large size and population, but unusually dense and large settlements as well as vast barely populated regions within the continent of 4.4 billion people. The boundaries of Asia are traditionally determined as that of Eurasia, as there is no significant geographical separation between Asia and Europe. The most commonly accepted boundaries place Asia to the east of the Suez Canal, the Ural River, and the Ural Mountains, and south of the Caucasus Mountains and the Caspian and Black Seas.[4] It is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean and on the north by the Arctic Ocean.

Europe Europe is a continent that comprises the westernmost part of Eurasia. Europe is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west, and the Mediterranean Sea to the south. To the east and southeast, Europe is generally considered as separated from Asia by the watershed divides of the Ural and Caucasus Mountains, the Ural River, theCaspian and Black Seas, and the waterways of the Turkish Straits.[5] Yet the borders of Europe—a concept dating back to classical antiquity—are arbitrary, as the primarily physiographic term "continent" also incorporates cultural and political elements.

North AmericaNorth America is a continent entirely within the Northern Hemisphere and almost all within the Western Hemisphere. It can also be considered a northern subcontinent of the Americas.[2] It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the west and south by the Pacific Ocean, and to the southeast by South America and the Caribbean Sea.

Oceania Oceania is a region centered on the islands of the tropical Pacific Ocean.[4] Opinions of what constitutes Oceania range from its three subregions of Melanesia, Micronesia, and Polynesia[5] to, more broadly, the entire insular region between Southeast Asia and the Americas, including Australasia and the Malay Archipelago.[6]

South AmericaSouth America is a continent located in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It is also considered as a subcontinent of the Americas,[1] which is the model used in Spanish-speaking nations and most of South America.

The Water• Water is a transparent fluid which forms the

world's streams, lakes, oceans and rain, and is the major constituent of the fluids of organisms. As a chemical compound, a water molecule contains one oxygen and two hydrogen atoms that are connected by covalent bonds. Water is a liquid at standard ambient temperature and pressure, but it often co-exists on Earth with its solid state, ice; and gaseous state, steam (water vapor). It also exists as snow, fog, dew and cloud.