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Karnataka 1st PUC Geography Question Bank Chapter 6 Hydrosphere
1st PUC Geography Hydrosphere Text Book Questions and Answers
I. Answer the following in a word or a sentence each.
Question 1.
What is Hydrological cycle?
Answer:
The cyclic (evaporation, Condensation and precipitation) movement of water between the atmosphere and the Earth surface is called Hydrological cycle.
Question 2.
Define Oceanography.
Answer:
The scientific study of water bodies (Seas, oceans etc.)
Question 3.
Which instrument is used to measure depth of the Ocean?
Answer:
Fathometer.
Question 4.
Name the region which covers largest area in the ocean floor.
Answer:
Deep sea plains cover the largest area of the ocean floor (82. 7%).
Question 5.
What is Salinity?
Answer:
The total amount of dissolved solids (minerals) in the ocean.
Question 6.
Which lines are drawn on the map to show places having same salinity?
Answer:
Isolines.
Question 7.
What are Sea waves?
Answer:
Sea waves are the undulations formed on the surface of the sea or ocean formed due to the influence of wind and friction of the surface of ocean water.
Question 8.
Where do we find the ‘Agulhas current’?
Answer:
From East of South Africa to Cape of Good Hope in the southern tip of Africa.
Question 9.
How does a tide occur?
Answer:
Tides are caused by the:
- The gravitational force of the moon
- The gravitational force of the sun
- the centrifugal force of the earth
which causes the regular rise and fell of water level in the world’s sea and oceans.
Question 10.
What is Tidal period?
Answer:
Tidal period is the time between successive high tide and low tide the internal between two high tides and two low tides is around 12 hours and 26 minutes and between one high tide and low tide is around 6 hours and 13 minutes. In a period of 24 hours and 52 minutes, 2 high tides and two low tides occur.
II. Answer the following in two or three sentences each.
Question 1.
Name the four submarine relief features of the Ocean floor.
Answer:
The major submarine relief features are,
- The Continental shelf: The shallow submerged extension of the continent.
- The continental slope: The steep slope extending to the ocean basin floor from the continental shelf.
- The deep-sea plains: Avast level or plain area found between the continental slope and ocean deep.
- The Ocean Deep or Trench: An are shaped depression in the deep ocean floor.
Question 2.
Mention the important features of Continental Shelf. Features of the continental shelf.
Answer:
- It is the shallowest part of the ocean with depth varying between 20 to 600m.
- Its width vary from one ocean to another ranging between 65 to 75 km.
- The width of the shelf is often related to slope of the adjacent land.
- They are covered with thick deposits of silt, sand, mud and sediments derived from the land.
- Continental shelves occupy about 7.6% of the ocean floor.
- Natural resources like oil, natural gas are found in the continental shelf.
Question 3.
Why is Ocean deep or Trench important in the Ocean bottom?
Answer:
Earthquakes and Tsunamis take birth in the Ocean deep or Trenches which help in the formation of land forms.
Question 4.
State any four factors that influence on the distribution of temperature in the ocean.
Answer:
Factors affecting the distribution of temperature are
- Latitudes
- Prevailing winds
- Ocean currents
- water salinity.
Question 5.
Mention any four dissolved minerals in the Ocean water.
Answer:
The dissolved minerals in ocean water are:
- Sodium chloride
- Magnesium chloride
- Calcium Sulphate
- Potassium sulphate.
Question 6.
What factors affect the salinity in the Ocean water?
Answer:
Factors affecting the salinity of ocean water are
- Evaporation
- Precipitation
- Freshwater mixing with ocean water
- Trade winds.
Question 7.
Name the two types of Ocean currents. Where are they found?
Answer:
Ocean currents are of two types (based on latitude and temperature)
Warm Currents:
Which are the high temperature ocean currents flowing from the equational regions to polar regions.
Question 8.
Mention any four South Indian Ocean currents.
Answer:
South Indian Ocean Currents:
- Mozambique Current
- Madagascar Current
- Agulhas Current
- West Australian cold Current.
Question 9.
Distinguish between High tide and Low tide.
Answer:
- High tide: The rise in sea level due to the Gravitational attraction of the sun or moon and the centrifugal force of the Earth.
- Low tide: The fall in the sea level.
Question 10.
Mention any four uses of tides.
Answer:
- Tides increase the depth of water in shallow harbours and help navigation during high tides.
- Tides clean the entrance of ports, harbours and river mounths.
- Tides help fishing and other aquaculture activities.
- Tides promote salt and foam production in the coastal areas.
III. Answer the following.
Question 1.
Explain the topography of the Ocean floor with a diagram.
Answer:
The surface beneath the water is characterized by a great diversity of relief (topography) features. The major submarine relief features are:
- The Continental Shelf
- The Continental Slope
- The Deep Sea Plains and
- The Ocean Deep
1. The Continental Shelf:
The shallow submerged extension of continent is called the continental shelf It is the shallowest part of the ocean with depth varying between 20 to 600 m. Its width vary from one ocean to another ranging between 65 to 75 km. The width of the shelf is often related to slope of the adjacent land.
It is wide along the low lying land and narrows along the mountainous coasts. Nearly 70% of continental shelves are covered with thick deposits of silt, sand, mud and sediments derived from the land. This region occupies about 7.6% of the ocean floor. Many ports and harbors, major fishing grounds and natural resources like oil, natural gas etc., are found in the continental shelf.
2. The Continental slope:
The steep extending to the ocean basin floor from the continental shelf is called the continental slope. It is characterized by gradients of 2-5°. The continental slope makes a boundary between the continental crust and the ocean crust. The depth of water in this region varies from 200 to 2000m.
This region covers an area of about 8.5% of the ttotal area of the ocean floor. The most outstanding land feature found in the continental slope are submarine canyons.
3. The Deep Sea Plains:
A vast level or plain area found between the continental slope and the ocean deepsea plains. This region lies between 3000 and 6000 m below the surface of the ocean. Deep sea plains account for about 82.7% of the total area of the ocean floor. Sea mounts, ridges, and guyots are the outstanding land features in this region.
4. The Ocean Deep or Trench:
An arc-shaped depression in the deep ocean floor, is called ocean deep or trench. These are the deepest parts of the ocean floor. Ocean trenches are produced by the subduction of oceanic crust under continental crust. They resemble steep-sided valleys or canyons on the land. Trenches or deeps are generality parallel to the coasts feeing mountains and along the islands.
Great earthquakes and tsunamis generally take birth in this region. About 1.2% of the ocean floor is covered by trenches. Its depth vary from 6000 to 8000m. As per the records 57 deeps have been identified in the ocean floor. Of these 32 are in the pacific ocean, 19 in the Atlantic ocean and 6 in the Indian ocean.
Question 2.
Describe the salient features of Salinity of the Ocean water.
Answer:
The total amount of dissolved solids (minerals) in the ocean water is called salinity. The ocean’s salinity consists of various elements. They are Sodium chloride, Magnesium chloride, Magnesium sulfate, Calcium carbonate, Magnesium bromide etc. Of these Sodium chloride (77.8%) is the most important constituent.
Factors affecting the salinity in the ocean water are:
- Evaporation: High evaporation in the ocean water leads to high salinity
- Precipitation: High rainfall and snowfall in the oceans lowers the salinity
- Freshwater mixing with ocean water: Continuous mixing of dissolved salts by running water (river), Groundwater and glaciers increase the percentage of salt content in the ocean
- The trade winds drive away saline water to less saline areas resulting in the variation of salt content.
Distribution of Salinity:
The average salinity of the ocean water is 35ppt (parts per thousand), means 35 Grams of salt per 1000 grams of sea or ocean water. The amount of salt content varies from one ocean to another. The average salinity of the Atlantic ocean is around 36ppt, the pacific ocean is 35ppt and the Indian ocean is 35ppt.
Latitude, precipitation, mixing of freshwater, etc., influence on the horizontal and vertical distribution of salinity. The regions near the Tropic of Cancer and Capricorn record high salinity due to high temperature, more evaporation, low rainfall and extensive arid and semi-arid areas, while the equatorial region record low salinity because of high temperature and high rainfall. The polar region record the least salinity due to very low temperature, evaporation and less rainfall.
Isohalines are the lines drawn on the map to show the places having the same amount of salinity.
Question 3.
Explain the Indian Ocean currents with the help of Maps.
Answer:
Indian Ocean is the third largest ocean on the Earth. It is situated between the continents of Africa, Asia and Australia. This ocean is mainly found in the southern hemisphere but a small portion is in the northern hemisphere. Indian ocean is bordered by land in the north and open to water in the south. The currents of this ocean is influenced by the shape of the land mass and monsoon winds.
The Indian ocean currents are of two types:
- North Indian Ocean currents and
- South Indian Ocean currents.
1. North Indian Ocean currents:
The ocean currents of the North Indian ocean is very closely influenced by the monsoon winds. The direction of ocean currents get reversed as a result of monsoonal change of air streams. The south west monsoon and north east monsoon winds change the direction of north Indian Ocean currents twice a year.
In the summer season south west monsoon winds influence on the flow of North Indian ocean water from the Arabian Sea to Bay of Bengal. The currents (Arabian sea-warm) flow in a clockwise direction along the east coast of Somalia- Somalia current, Gulf of Aden, brushes the western and eastern coasts of India (Arabian sa and Bay of Bengal currents) and finally joins North Equatorial current.
In the winter season, the monsoon winds get reversed, blow from north east to south west. Hence the ocean currents flow from the western coast of Thailand and Myanmar and brushes the eastern and western coast of India as North east currents (warm), passes along Gulf of Aden, Somalia and finally reaches North Equatorial currents in anti-clockwise direction.
2. South Indian Ocean currents:
The currents of the South Indian ocean are not affected by the monsoon winds. The South Equatorial current flows from the Indonesian archipelago towards the eastern coast of Africa. After reaching Madagascar it is divided into two branches:
- Mozambique current (warm): Flows between Africa and Madagascar in the Mozambique channel
- Madagascar current (warm): Flows in the east coast of Madagascar towards south.
These two currents meet in the east of South Africa and form ‘Agulhas current’ (warm). This current further flows southward and reach Cape of Good Hope in the south tip of Africa. In the south of Indian ocean West wind drift flows towards Australia due to the influence of westerlies.
After reaching Australia it separates into two branches as: a) West Australian cold current Moving northward in the west coast of Australia and finally joins South Equatorial current b) West wind drift (warm) – Flows to the south of Australia and finally merges into the Pacific west wind drift.
Question 4.
Briefly explain the types of tides.
Answer:
Types of Tides:
The tides are of different height and magnitude in different regions of the sea or ocean. In the open ocean its height is different compared to closed water bodies. On the basis of the strength of gravitational attraction by the Sun and the Moon tides are classified into two types:
- Spring tides
- Neap tides
1. Spring tides:
These tides occur during full moon and new moon days. When the Sun, Moon and the Earth are in a Straight line (Syzygy), the gravitational attraction by the Sun and the Moon together act on the water bodies of the Earth. Therefore, the water level in the ocean or sea rises to maximum height causing very high tidal forces known as ‘Springtides’. Every month two spring tides occur with a gap of 15 days each.
2. Neap tides:
These tides occur on the days when the moon is in first quarter or in the third or last quarter. When the Sun and the Earth are in a straight line and the Moon is perpendicular (right angle) to the Earth the gravitational force of the Moon and the Sun will be in opposite direction.
Therefore, the minimum pull is exerted on the seas and oceans. This results in the formation of low tidal forces known as ‘Neap tides’. Every month two neap tides occur with a gap of 15 days each.
Question 5.
What is the conservation of the Ocean? Mention the important measures.
Answer:
The conservation of Ocean is the conservation of the marine resources. It is the protection and preservation of ecosystems in oceans and seas. It focuses on restoring damaged marine ecosystems, and the preservation of vulnerable marine species. Ocean conservation focuses on issues such as extinction and habitat change.
In-depth study of conservation physical and biological marine resources and ecosytem functions. Ocean conservationists rely on a combination of scientific principles derived from marine biology, oceanography and fishery sciences, as well as human factors such as demand for marine resources and marine law, economics and policy in order to determine how to best protect and conserve marine species and ecosystems.
In the prehistoric period, people used to live near the sea or ocean coast to use marine resources. Traditionally man used the oceans for fishing(food), transportation and defence. Fishing and transportation have been the two most important economic activities of man for a very long time.
Oceans are the storehouse of various resources, which man is using in an unplanned and non-judicious manner. The exploitation of the marine resources are in the form of extraction of minerals like crude oil, natural gas, thorium, magnetite, common salt, generation of power in the form of wave energy, tidal energy, biomass conversion and marine food resources like fish, plankton, animals, seaweeds etc.,
Overpopulation, unplanned economic development, exploitation resources, territorial and marine boundary supremacy, nuclear test etc., have resulted in fear and threat to marine organisms, resources, configuration of coastal areas etc., To control the exploitation and pollution in the sea or ocean, conservation of Ocean is very much necessary and important.
A few measures recommended by the experts are:
- Sewage disposal must be regulated and treated.
- Oil leakage has to be brought under control.
- Disposal of toxic metals, pesticides must be reduced.
- Radioactive or Nuclear mineral dumping must be stopped
- Coastal mining activities have to be regulated and monitored
- Over fishing, aquaculture activities have to be controlled
- Unwanted battles and wars, military establishments near the coasts have to be reduced.
- Literacy and education programmes on marine features must be initiated and promoted.
- Proper law to be enacted to save sea and ocean.
- World wide awareness program must be arranged to show the pros and cons of marine pollution etc.,