Major Domains of the Earth – Atmosphere
The earth is a very complex place. It has been divided into four sphere, to enable us to understand it separately and how each sphere interacts with each other.
What are the four major domains of the earth?
The four major domains are divided as :
- Lithosphere – Lithosphere is the solid shell of the earth and is divided into a crust and mantle.
- Atmosphere – Atmosphere is a layer of gases surrounding a planet, held in place by the gravity of the body.
- Hydrosphere – Hydrosphere is the combined mass of water present on the surface or under the surface, on a planet.
- Biosphere – Biosphere also known as the ecosphere, is all the connected ecosystems on a planet and includes all living beings, including their interaction with the other spheres.
What is atmosphere?
Atmosphere is a collection of gases that make the earth habitable.
It consists of 78% nitrogen, 21% oxygen, 1% water vapour and some percentages of trace gases like argon, helium, neon and carbon dioxide. All of these gases combine to form a layer that we refer to as the earth’s atmosphere. It helps protect life on earth by creating pressure, allowing liquid water to exist on the earth’s surface, absorbing ultraviolet solar radiation, warming the surface through heat retention and reducing extreme temperature between day and night.
5 Layers of atmosphere
The atmosphere is comprised of 4 layers, based on temperature, and another layer 500 kms above the earth’s surface, called the exosphere. They are :
1. Troposphere :
The lowest part of the atmosphere, the troposphere contains most of our weather clouds, rain, snow. In this part, temperatures drop by 6.5 degrees celcius, at every km elevation. The sun’s heat is insulated and weathers are created in this layer.
2. Stratosphere :
The stratosphere extends from after the tropopause, the upper boundary of the troposphere. The stratosphere is crucial to life on earth, as it contains the ozone layer, which protects against UV rays from reaching the earth’s surface. Very few clouds are found in this layer. Jets fly in this layer of the atmosphere, to avoid turbulence found in the troposphere.
3. Mesosphere :
The mesosphere is one of the least studied layers of the atmosphere, as flights and balloons do not fly in this layer and satellight are in layers above this one. Meteors that stream into the earth’s atmosphere, are generally burnt up, by the time they reach this layer and cannot travel further. The mesosphere does experience special clouds – noctilucent clouds and the presence of lightning, called elves and sprites.
4. Thermosphere :
- The thermosphere is the layer of the earth’s atmosphere directly above the mesosphere. The small particles of gas present in the layer absorb x – rays and ultra violet radiation from the sun. Thermosphere means heat sphere, and temperatures in the sphere can go upto 1000 degree celcius.
- The lowest part of the thermosphere, from 80 km to 600 km and more, is the layer that contains ionised air and is called ionosphere. The sun’s rays in this part of the atmosphere are so strong, they break apart molecules and atoms of air, leaving ions (atoms with missing electrons) and free floating electrons.
- The ionosphere is the region of the atmosphere where the aurorae occur. Aurorae occurs in both Northern and Southern hemisphere. The phenomenon is known as aurora borealis, or northern lights at the north pole and it is known as aurora australis or southern lights, at the south pole.
- Aurora is caused by high energy particles streaming out from the sun – the solar wind – striking the earth’s upper atmosphere, or ionosphere. Energy from these electrically charged particles is converted into light, forming visible glows, rays, arcs, bands and veils. The light is generally greenish, but sometimes it is also red. The charged particles are attracted by the earth’s magnetic field. The aurorae are witnessed near the magnetic poles and some distance close to it.
5. Exosphere :
The exosphere is the last layer of the atmosphere. The exosphere extends to 10,000 km above the earth’s surface. In this layer, hydrogen and helium are the main components and particles are constantly escaping into space from this layer of the atmosphere. Several satellites orbit the earth in this layer.