Class 7 Geography Chapter 4 Air Pressure Answers
Maharashtra Board Class 7 Geography Solutions Chapter 4 Air Pressure
Balbharti Maharashtra State Board Class 7 Geography Solutions Chapter 4 Air Pressure Notes
Textbook Exercise Important Questions and Answers
Maharashtra State Board Class 7 Geography Solutions Chapter 4 Air Pressure
Class 7 Geography Chapter 4 Air Pressure Textbook Questions and Answers
Q. 1. Give reasons:
(1) Air pressure decreases with increasing altitude.
Answer: The proportion of dust in the air, water vapour, heavy gases, etc. is higher in the air closer to the surface of the earth. This proportion decreases with increasing altitude. As one moves higher and higher from the surface of the earth, the air becomes thinner and thinner. As a result, the air pressure decreases with increasing altitude.
(2) Pressure belts oscillate.
Answer: The duration and the intensity of sunrays varies during particular periods of the year in both the hemispheres. As a result, the locations of the temperature zones and the pressure belts dependent on the sun’s heat also vary. This change is of the order of 5° to 7° towards north in Uttarayan, and 5° to 7° south in Dakshinayan. Therefore the pressure belts oscillate.
2. Give short answers to the following questions.
(1) What effect does temperature have on air pressure?
Answer: Temperature and air pressure are closely related. Wherever the temperature is high, the air pressure is low. As the temperature rises the air gets heated, expands, and becomes lighter. This lighter air in the vicinity of the earth’s surface starts moving up towards the sky. As a result, the air pressure in such areas decreases.
(2) Why is the subpolar low pressure belt formed?
Answer: Due to earth’s curvature, the area between two parallels gets reduced as we move towards the poles. This results in lesser friction of the air with the earth’s surface. Air in this region is thrown out because of this reduced friction and also because of the earth’s rotational motion. This leads to the development of a low pressure belt. This condition is observed in the area between 55° and 65° parallels in both the hemispheres.
3. Write notes on:
(1) Mid-latitudinal high pressure belts.
(i) The heated air becomes lighter, starts ascending and after reaching higher altitudes, moves towards the polar region, i.e., towards the North and the South Pole.
(ii) Due to low temperatures at the higher altitudes, the air cools down and becomes heavier. This heavier air descends down in both the hemispheres in the region between 25° to 35° parallels.
(iii) This leads to the formation of high pressures belts in these parallels of latitudes in both the hemispheres.
(iv) This air is dry, hence the region does not get rainfall.
(v) Consequently, most of the hot deserts on the earth are found in these regions.
(2) Horizontal distribution of air pressure.
(i) The heat received from the sun is uneven in different regions.
(ii) Hence the distribution of the temperature is uneven from the equator to the poles.
(iii) As a result, the temperature zones are created.
(iv) Equatorial low pressure belt is formed between the parallels 5° north and 5° south.
(v) Mid latitudinal high-pressure belt is formed between 25° and 35° parallels due to descending heavier air.
(vi) Subpolar low-pressure belt is formed between 55° and 65° parallels due to friction and rotation.
(vii) Polar high-pressure belt is formed between 80° and 90° parallels due to low temperatures.
4. Fill in the gaps with the appropriate option.
(1) At higher altitudes air becomes ________. (thicker, thinner, hotter, more humid)
(2) Air pressure is expressed in _______ .(millibars, millimeters, milliliters, milligrams)
(3) On the earth, air pressure is _______.(uniform, uneven, high, low)
(4) The ______ pressure belt spreads between 5° North and 5° South parallel. (equatorial low, polar high, subpolar low, mid-latitudinal high)
Answer: equatorial low