Hydroshpere
Class 9
Q1. Give a reason for each of the following:
a. Winds are the main influence on the circulation of ocean currents .
a. Winds are the main influence on the circulation of ocean currents .
Ans. Planetary winds or Permanent Prevailing Winds are the primary cause of the circulation of the Ocean Currents. Most of the ocean currents of the world follow the direction of prevailing permanent or planetary winds.
Winds drag the surface water in the same direction where these blow due to the force of friction, which leads to the formation of ocean currents.
b. Alaskan coast reman ice-free in winter.
Ans. Alaskan coast reman ice-free in winter because of the influence of the warm Alaskan current. It keeps the Alaskan coast warm and ice free.
c. Rich fishing are located in the areas where cold and warm currents meet.
Ans. The mixing of the cold and warm currents provides ideal temperature condition for the life of the fish. The chief food of fish - plankton is found in abundance in such areas.
Q2. How do variations in sea water salinity cause ocean currents?
Ans. The amount of salts contained in sea water vary from one part of the ocean to another. The high salinity water tends to subside and move below water of low salinity causing ocean currents.
Q3. Give a brief note on the following:
a. Spring tide
Ans. They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon. The
Winds drag the surface water in the same direction where these blow due to the force of friction, which leads to the formation of ocean currents.
b. Alaskan coast reman ice-free in winter.
Ans. Alaskan coast reman ice-free in winter because of the influence of the warm Alaskan current. It keeps the Alaskan coast warm and ice free.
c. Rich fishing are located in the areas where cold and warm currents meet.
Ans. The mixing of the cold and warm currents provides ideal temperature condition for the life of the fish. The chief food of fish - plankton is found in abundance in such areas.
Q2. How do variations in sea water salinity cause ocean currents?
Ans. The amount of salts contained in sea water vary from one part of the ocean to another. The high salinity water tends to subside and move below water of low salinity causing ocean currents.
Q3. Give a brief note on the following:
a. Spring tide
Ans. They occur when the Earth, the Sun, and the Moon are in a line. The gravitational forces of the Moon and the Sun both contribute to the tides. Spring tides occur during the full moon and the new moon. The
high tides are very high and the low tides are very low.
b. Neap tide
Ans. When the moon is in a position that is at right angles to the sun, the gravitational pull of the two bodies are working in opposing directions on the Earth’s surface. This is when the gravitational forces of the sun and the moon are working against each other and we experience moderate changes in water levels. We refer to this period in the lunar cycle as neap tides which occur during quarter moons.
c. Labrador Current
Ans. It is an important cold water current of the North Atlantic Ocean, which has its origin in the Arctic ocean which flows from the North to the South between the Greenland and the Baffin Island . Passing southwards, it merges with the Gulf Stream near Newfoundland. The average speed of the current is about 28 km per day. It brings down huge icebergs from the Arctic Ocean to the eastern coast of Canada which are hazardous to navigation.
b. Neap tide
Ans. When the moon is in a position that is at right angles to the sun, the gravitational pull of the two bodies are working in opposing directions on the Earth’s surface. This is when the gravitational forces of the sun and the moon are working against each other and we experience moderate changes in water levels. We refer to this period in the lunar cycle as neap tides which occur during quarter moons.
c. Labrador Current
Ans. It is an important cold water current of the North Atlantic Ocean, which has its origin in the Arctic ocean which flows from the North to the South between the Greenland and the Baffin Island . Passing southwards, it merges with the Gulf Stream near Newfoundland. The average speed of the current is about 28 km per day. It brings down huge icebergs from the Arctic Ocean to the eastern coast of Canada which are hazardous to navigation.