# WBBSE Class 10 Geography Solutions Chapter 2.2 Layers of the Atmosphere

Detailed explanations in West Bengal Board Class 10 Geography Book Solutions Chapter 2.2 Layers of the Atmosphere offer valuable context and analysis.

## WBBSE Class 10 Geography Chapter 2.2 Question Answer – Layers of the Atmosphere

Answer in short : 2 Marks

Question 1.
Name the different layers of the atmosphere.
The different layers of the atmosphere are – Troposphere, Stratosphere, Mesosphere, Ionosphere or Thermosphere and Exosphere.

Question 2.
What is the Tropopause?
Tropopause is the transition zone between the troposphere and the stratosphere. It extends for about 2-3 km. Here the temperature remains constant.

Question 3.
What is the Stratopause?
Stratopause is the transition zone between the stratosphere and the mesosphere. Temperature in this zone remains constant.

Question 4.
What is the mesopause ?
Mesopause is the transition zone between the mesosphere and the ionosphere or the thermosphere. Temperature in this zone remains constant.

Question 5.
What is the ozone layer ?
There is a layer in the stratosphere at a height of 20-45 km, which has a high concentration of ozone gas. This portion of the stratosphere is called the ozone layer or the ozonosphere.

Question 6.
Describe the exosphere.
The exosphere lies above the thermosphere and extends up to 960 km. It gradually merges with the interplanetary space.

Question 7.
What is normal lapse rate?
A lapse rate is the rate at which temperature of the atmosphere decreases as the altitude increases in troposphere. Temperature decrease at the rate of 6.4°C per 1000 mt. in the troposphere.

Question 8.
What is the Van Allen radiation belt ?
Energetic charged particles mostly originated from solar wind are captured by and held around the planet earth called Van Allen radiation belt. Earth has two such belts.

Question 9.
What do you mean by nacreaous cloud ?
One of the polar stratospheric clouds, that consist of only ice crystals are called nacreous cloud. These are not harmful. These are mostly observed during twillight. These are not precipitation cloud.

Answer in briefly : 3 Marks

Question 1.
Describe the Troposphere.
The lower-most layer of the atmosphere lying closest to the earth’s surface is called the Troposphere. It extends up to 18 km at the equator and 8 km at the poles. Temperature decreases by 6.4°C with rise of every 1000 m or 1 km. This is called the lapse rate of temperature. Most of the weather phenomena occur in this zone. Eg. – clouds, rainfall, storms etc.

Question 2.
Describe the stratosphere.
The second layer of the atmosphere that lies above the troposphere and extends up to 80 km above the earth’s surface is called the stratosphere. In this zone, temperature goes on increasing with increase in height (about 4°C for every 50 km). A significant concentration of ozone gas is found in this layer, known as the Ozonosphere. Stratosphere has very less atmospheric disturbances. Some cirrus clouds form in the lower levels of this layer.

Question 3.
Describe the mesosphere.
The third layer of the atmosphere that lies above the stratosphere is known as the mesosphere. This zone is marked by decrease in temperature with height. This is the coldest layer of the atmosphere. Meteors that come from the outer space towards the earth get burnt within this layer.

Question 4.
What are the characteristics of the ozone layer?
The ozone layer is a part of the stratosphere. The main characteristics of this layer are :

1. Ozone constitutes about 1% of the stratospheric air.
2. Ozone is produced by the action of solar radiation on ordinary oxygen atoms.
3. Ozone layer acts as a shield, protecting us by absorbing most of the harmful ultra-violet rays of the sun.
4. Density of ozone gas is expressed by the ‘Dobson’ unit (DU). Lowest density of the layer is found in the equatorial region.

Question 5.
What do you mean by ozone depletion and ozone hole.
Depletion or breaking of ozone molecules in the atmosphere is known as ozone depletion.

1. Average natural concentration of ozone dropped by 50% in 1987.
2. In some areas, the ozone layer totally disappeared which resulted in formation of ozone-less patches. These hollows are called ozone holes.
3. The chloro fluoro carbons (CFCs) are the chief culprits causing ozone depletion.

Question 6.
Mention the characteristics of the lonosphere.