Earth System : Types of Spheres of Earth

Spheres of Earth

Introduction

Earth is the place where we live. It is the third planet from the sun. 70% of Earth is covered by water. The planet Earth is made of sub-system called spheres. There are 5 spheres on the Earth. They are geosphere, atmosphere, hydrosphere, biosphere, and cryosphere. All the spheres of Earth interact with each other. Earth’s spheres do not work individually.  The action of one sphere affects the other sphere. Humans can have major effects on various spheres of the Earth. For example: burnig of fossil fuels cause lot of air pollution(atmosphere). Dumping waste into water bodies cause water pollution (hydrosphere). Accumulation of waste in landfills disturbs the geosphere. All these effects finally disturbs the ecosystem (biosphere). 

Types of Spheres on Earth

The geosphere is also known as the lithosphere. All the natural forms, such as mountains, oceans, glaciers, hills, valley, canyons, sand dunes, plains, plateaus, present on the  Earth’s land constitutes the lithosphere. These natural forms are called landforms.  

Various landforms on Earth – Mountains, plains, and plateau

The hydrosphere includes Earth’s water. 97% of the Earth’s water is salt water present in the oceans. Freshwater is present in aquifers, lakes, rivers, and glaciers. Earth’s water always move through a water cycle. Water evaporates from the surface of the earth into the atmosphere in the form of gas. In the atmosphere, water condenses and forms cloud. As the number of water droplets increase in the clouds, it falls back to the earth as rain, sleet, hail, or snow (precipitation). Then some water flows into lakes, rivers, and oceans, whereas some water seeps into the soil and ground. 

Atmosphere: The blanket of air around the earth is called atmosphere. Atmosphere is a mixture of gases. Major area of the atmosphere is covered by nitrogen (78%), oxygen (21%) and other gases (1%). The other gases include water vapor and carbon dioxide, that are essential for earth’s water cycle. Earth’s atmosphere comprises  of different layers. The layer closest to the earth is troposphere. In this region air is always on the move and wind is a gentle breeze. Weather changes by change in wind direction. 

layers of earth’s atmosphere

Biosphere: It includes all living things on the earth such as plants, animals, fungi, and microscopic plankton. Life on earth is close to all the spheres of earth, where it can use oxygen(atmosphere), carbon dioxide (atmosphere), sunlight (atmosphere), water (hydrosphere), minerals (lithosphere) and organic matter (lithosphere). Between the land, water habitat and ocean, the biosphere is divided into biomes. A biome is a place on the earth that depends upon the rainfall and temperature, and help living things to grow well in that habitat.  

Cryosphere: There are some places on Earth that are very cold where water is present in frozen solid state. These areas of snow or ice are the areas where the temperatures fall below 0°C (32ﹾF) for at least some part of the year. So, cryosphere is the solid (frozen) part of the earth’s system. 

One part of the cryosphere is ice and snow. This comprises of the largest parts of the cryosphere, the continental ice sheets that are found in Greenland and Antarctica. Also, ice caps, glaciers, and areas of snow and permafrost, are as well found in these regions. When continental ice melts and flows from land and goes to the sea surface, we get shelf ice. 

There is also ice that is found in water is the other part of the cryosphere. This comprises of frozen parts of the ocean, such as waters encircling Antarctica and the Arctic. It also comprises of frozen rivers and lakes that primarily occur in polar regions. 

The elements of the cryosphere play a significant role in the Earth’s climate. Snow and ice reflect heat from the sun, that helps to regulate the Earth’s temperature.  

Biogeochemical cycles 

There are some types of atoms that can be a part of a plant, an animal, part of a river’s water etc. These atoms can be a part of both living things as well as non-living things such as water, air, and even rocks. So, the same atoms are recycled over and over in several parts of the Earth. This kind of cycle of atoms between living and non-living things is known as a biogeochemical cycle. 

Biogeochemical cycle consists of all the atoms that are building blocks of living things. The carbon cycle and nitrogen cycles are the most common cycles. 

Small atoms of carbon and nitrogen are able to move around the Earth all the way through these cycles. For example, ocean water absorbs an atom of carbon from the air, and it is used by tiny floating plankton in the process of photosynthesis to prepare the food. There is a chance that this tiny carbon atom becomes part of the plankton’s skeleton, or a part of the large animal’s skeleton that eats planktons. Hence when the living things die and only bones are left behind, it becomes the part of a sedimentary rock. Carbon that is a part of rocks and fossil fuels such as oil, coal, and natural gas may be held away from the rest of the carbon cycle for a long time. These long-time storage areas are called “sinks.” When we burn fossil fuels, carbon that had been present underground is sent into the atmosphere as carbon dioxide, that is a greenhouse gas. 

The Carbon Cycles 

The carbon cycle can be very easily understood by two interconnected sub-cycles: 

• One carbon cycle deal with rapid exchange of carbon among living things. 

• Second carbon cycle deals with long-term cycling of carbon through various geologic activities. 

The carbon element is a component of seawater (Hydrosphere), the air (Atmosphere), soils (Geosphere), all living things (Biosphere) and rocks like limestone and coal (Geosphere). On earth, carbon is able to move from one of these spheres to another as a part of the carbon cycle. 

The Biological Carbon Cycle: 

• From the atmosphere, carbon goes to the plants. In the atmosphere, carbon is attached to oxygen gas in the form of carbon dioxide (CO₂). By the method of photosynthesis, carbon dioxide gas from the air is absorbed by the plant, to produce food for the growth of plants. 
• Carbon moves from plants to animals through the food chain.  

 

• From plants and animals [Biosphere], carbon moves to soil [Geosphere]. After the death of plants and animals, their bodies, wood, leaves, decomposes, and bring the carbon into the ground. In millions and millions of years some dead and decayed plants and animals get buried and become fossil fuels. 
• The movement of carbon is from living things [Biosphere] to the atmosphere. Every time when animals exhale, the carbon dioxide gas (CO₂) is released into the atmosphere. Plants and animals need to get rid of carbon dioxide gas by the process of respiration. 
• When fuels are burned, carbon moves from fossil fuels to the atmosphere. Most of the carbon quickly enters the atmosphere as carbon dioxide gas by burning fossil fuels to power factories, powerplants, cars and trucks. Every year, five and a half billion tons of carbon is released in the atmosphere by burning fossil fuels. From this huge amount, 3.3 billion tons stays and the remaining CO₂ dissolve in seawater. 
• Carbon goes from the atmosphere to the oceans (Hydrosphere). The oceans and other water bodies absorb a certain quantity of carbon from the atmosphere and that carbon gets dissolved into the water. 

The Geological Carbon Cycle: 

The geological carbon cycle takes more time than the biological carbon cycle. Generally, it takes millions of years for carbon to cycle through the geological pathway. Carbon may be stored for long time in the atmosphere, water bodies – mostly oceans— ocean sediment, soil, rocks, fossil fuels, and interior of Earth. 

The level of carbon dioxide in the atmosphere is affected by the carbon reservoir in the oceans and vice versa. Carbon dioxide present in the atmosphere dissolves in water and reacts with water molecules as shown in the following reactions: 

CO₂​+H₂​O⇌H₂​CO₃​⇌HCO₃⁻​+H⁺⇌CO₃²⁻​+2H⁺ 

The carbonate released in this process combines with calcium ions to form calcium carbonate. It is a major part of the shells of marine organisms. After death of the organisms, their bodies may sink and ultimately become part of the sediment on the ocean floor. Over a period of geologic time, the sediment converts into limestone, which is the biggest reservoir of carbon on Earth. 

On land, carbon is stored in soil as organic carbon obtained by the decomposition of living things or as inorganic carbon by weathering of rock and minerals present on the ground. Fossil fuels are present deeper inside the ground such as oil, coal, and natural gas. These are the remains of plants decayed under anaerobic (in the absence of oxygen). Formation of fossil fuels takes millions of years to form. When humans burn fossil fuels, carbon is given out into the atmosphere in the form of carbon dioxide. 

There is another way for carbon to enter the atmosphere is by the volcanic eruptions. In the ocean floor, carbon containing sediments are taken deep within the Earth by the process called subduction. In this process, one tectonic plate moves under another and forms carbon dioxide, which can be given out into the atmosphere by volcanic eruptions or hydrothermal vents. 

Summary

• 70% of Earth is covered by water. The planet Earth is made of sub-system called spheres.
• The 5 spheres of the Earth are – Hydrosphere, geosphere, atmosphere, biosphere, and cryosphere.
• The action of one sphere affects the other sphere.
• Cycle of atoms between living and non-living things is known as a biogeochemical cycle.
• On Earth, carbon is able to move from one sphere to another as a part of the carbon cycle.
• The carbon cycle is the process through which carbon goes from the atmosphere into the Earth and to organisms and then back again.