Atmosphere

An atmosphere contains the air that we breathe and is a blanket of gases that surrounds Earth. It is held near the surface of the planet by Earth’s gravitational attraction. A barometer is used to measure air pressure. Argon, oxygen and nitrogen from the three main constitutions of the atmosphere. In this article, let us know in detail about the atmosphere.

Looking for other study material?

Table of Contents:

• What is Atmosphere
• Layers of Atmosphere
• What Would Happen If The Earth’s Atmosphere Disappeared
• Composition Of Atmosphere – Gases In The Atmosphere
• Frequently Asked Questions – FAQs

What is Atmosphere?

An atmosphere is a blanket of gases that surrounds Earth. It is held near the surface of the planet by Earth’s gravitational attraction. Argon, oxygen and nitrogen from the three main constitutions of the atmosphere.

Definition

“Atmosphere is a protective layer of gases that shelters all life on Earth, keeping temperatures within a relatively small range and blocking out harmful rays of sunlight.”

Features of the Atmosphere:

• Helps retain the sun’s heat and prevents it from escaping back into space.
• Protects life from harmful radiation from the sun.
• Plays a major role in Earth’s water cycle.
• Helps keep the climate on Earth moderate.

There is no boundary between the atmosphere and outer space. The atmosphere gets less dense and denser until it “blends” into outer space.

Layers of Atmosphere

What do you see when you stand outside and look up? A blue sky? A group of clouds? At night you might see a crescent moon, stars, a satellite. What you are not seeing, however, is the complexity of our atmosphere.

The atmosphere has five distinct layers that are determined by the changes in temperature that happen with increasing altitude. Layers of Earth’s atmosphere are divided into five different layers as:

• Exosphere
• Thermosphere
• Mesosphere
• Stratosphere
• Troposphere

Let us find out more about the layers of atmosphere and their importance.

The hierarchical arrangement of various layers of the Earth’s atmosphere

Troposphere

The troposphere is the lowest layer in the atmosphere. It extends upward to about 10kms above sea level starting from ground level. The lowest part of the troposphere is called the boundary layer and the topmost layer is called the tropopause. The troposphere contains 75% of all air in the atmosphere. Most clouds appear in this layer because 99% of the water vapour in the atmosphere is found here. Temperature and air pressure drop as you go higher in the troposphere. When a parcel of air moves upwards it expands. When air expands it cools. Due to this reason, the base of the troposphere is warmer than its base because the air in the surface of the Earth absorbs the sun’s energy, gets heated up and moves upward as a result of which it cools down.

Stratosphere

Above the troposphere lies the stratosphere which extends from the top of the troposphere to about 50 km (31 miles) above the ground. The ozone layer lies within the stratosphere. Ozone molecules in this layer absorb high-energy ultraviolet (UV) light from the Sun and convert it into heat. Because of this, unlike the troposphere, the stratosphere gets warmer the higher you go! 

Mesosphere

Above the stratosphere is the mesosphere and it extends to a height of about 85 km (53 miles) from the ground. Here, the temperature grows colder as you rise up through the mesosphere. The coldest parts of our atmosphere are located in this layer and can reach –90°C.

Thermosphere

Thermosphere lies above the mesosphere and this is a region where the temperature increases as you go higher up. The temperature increase is caused due to the absorption of energetic ultraviolet and X-Ray radiation from the sun. However, the air in this layer is so thin that it would feel freezing cold to us! Satellites orbit Earth within the thermosphere. Temperatures in the upper thermosphere can range from about 500° C to 2,000° C or higher. The aurora, the Northern Lights and Southern Lights, occur in the thermosphere.

Exosphere

Exosphere is the final frontier of the Earth’s gaseous envelope. The air in the exosphere is constantly but gradually leaking out of the Earth’s atmosphere into outer space. There is no clear cut upper boundary where the exosphere finally fades away into space. 

Ionosphere

The ionosphere isn’t a distinct layer unlike other layers in the atmosphere. The ionosphere is a series of regions in parts of the mesosphere and thermosphere where high-energy radiation from the Sun has knocked electrons loose from their parent atoms and molecules

What would happen if the Earth’s Atmosphere disappeared?

Have you ever wondered what would happen if the Earth lost its atmosphere? Here is a breakdown of what could happen:

• Birds and Planes would fall from the sky. Although we can’t see air, it has a mass that supports flying objects.
• The sky would turn black. The sky gets its colour blue due to the atmosphere. Gases and particles in Earth’s atmosphere scatter sunlight in all directions. Blue light is scattered more than other colours because it travels as shorter, smaller waves. This is why we see a blue sky most of the time.
• There would be no sensation of sound. Although you could feel vibrations from the ground you wouldn’t hear anything. Sound requires a medium to travel.
• All the water bodies such as rivers, lakes and oceans would boil away. Boiling occurs when the vapour pressure of a liquid exceeds external pressure. In a vacuum, the water readily boils.
• Organisms that breathe air to survive would die. 

Composition of Atmosphere – Gases in the Atmosphere

The atmospheric composition of gas on Earth is largely conducted by the by-products of the life that it nurtures.

Dry air from earth’s atmosphere contains 0.038% of carbon dioxide, 20.95% of oxygen, 78.08% of nitrogen and 0.93% of argon.

Traces of hydrogen, neon, helium, nitrous oxide, ozone and other “noble” gases, but generally a variable amount of water vapour is also present, on average about 1% at sea level.

Click the video below to know in detail about the composition of the air.

Stay tuned to BYJU’S and FALL IN LOVE WITH LEARNING!