Earth’s Spheres

Earth’s Spheres 

Four major subsystems in the earth are- land, water, living things, or air. Everything in the earth belongs to at least one of them and in most cases, it belongs to more than one. The four systems are known as “spheres.” The name of the four spheres is- "lithosphere" (land), "hydrosphere" (water), "biosphere" (living things), and "atmosphere" (air). These four spheres are also subdivided into sub-spheres. This article shows a glimpse of the spheres only, not focusing on the sub-spheres.  

Lithosphere

The surface of our planet is formed with cold, hard, solid land. All of them are the parts of the lithosphere. It also contains the crust’s underneath semi-solid land and the center of the planet’s liquid land. The lithosphere’s surface is very irregular in shape. The irregularity is identified with three types of land shapes. They are- high mountain ranges such as Andes and Rockies, flat areas all over the globe and the deep valleys along the ocean floor. 

The prevailing three types of land are solid, semi-solid and liquid lands. They are different from each other with their physical and chemical structure. In this regard, an example of an onion can be taken. Like an onion, if someone cuts through the earth’s surface, he will find out three distinctive layers. The first layer on which we stand is loose soil containing nutrients, oxygen, and silicon. The next layer underneath is a thin crust made up of oxygen and silicon. The semi-solid layer is a thick one. This mantle is formed with oxygen, silicon, iron, and magnesium. The third layer is a liquid having an outer core of nickel and iron. The innermost layer is the center of the earth. This core has nickel and iron.   

The word “lithosphere” is a word with different meanings according to the user of the word. Some scientists related to the study of the geologic formations use the "lithosphere" to mean the cold, hard surface of the Earth. But here it is used to cover all the land’s spheres. 

Hydrosphere

The water of this planet can find in three types- solid, liquid, and gaseous water. All types of water are the parts of the hydrosphere. The average thickness of the earth is 10 to 20 kilometers. The range of the hydrosphere is from several kilometers downward to the earth’s surface into the lithosphere and about 12 kilometers upward into the atmosphere. 

Freshwater is found but not everywhere in the hydrosphere and most of this is frozen. The water cycle starts from the atmosphere as the beginning point is the flow of precipitation. Then it falls to Earth’s surface, flows through the rivers and streams and finally goes down the earth’s surface as groundwater.   

Most of the water in the hydrosphere is salty as per as Ninety-seven percent of Earth's water. 

The salty water is found in the deep valleys along Earth's surface. The temperature of the water depends on the ocean’s surfaces and thus it varies from place to place. Coldwater stays near the poles while very warm water is found near the equator. The change in physical water is the result of temperature differences. The water near the poles freezes because of the extreme cold. This water is found in solid forms like a polar icecap, a glacier, or an iceberg. The water near the equator evaporates into a gas because of extreme heat.   

According to some scientists, frozen water has its own sphere known as the "cryosphere." It combines glaciers, icecaps, and icebergs.  

Biosphere

All the living things on the earth are the parts of the biosphere. From microorganisms, plants to animals, all are the parts of this sphere.  

The term ecology is related to the biosphere. The ecological community in a certain surrounding of the biosphere is known as biomes. Within the biosphere, four types of biomes exist. They are deserts, grasslands, forests and water biomes.  

Each individual organism remains undetected from the space within the biosphere. But it is possible to detect the biomes from space. The areas which are covered with plants and which are not can be detected from space. 

"Anthroposphere" is a term used by the scientists to depict human’s own sphere. However, humans are an important part of all living things and thus they are included in the biosphere. 

Atmosphere

All the air in the Earth's system is part of the atmosphere. The range of this sphere starts from 1 m below the planet's surface to more than 10,000 km above the planet's surface. The topmost layer of the atmosphere protects the earth from the dangerous ultraviolet radiation from the sun. Heat emission and absorption are its continuous work to keep the earth’s temperature in check. The change in the lower portion of the atmosphere is the main reason behind weather variation. When the air in the lower portion is heated or cooled, it moves around the globe. The results may differ from a pleasant breeze to a terrifying tornado.  

The atmosphere is subdivided into many portions according to the chemical composition and temperature. But all the layers have not been discussed here.