MSBSHSE Class 8 Social Science Geography Chapter 4: Structure of Ocean Floor Textbook Questions and Solutions

Continents and oceans are a part of the lithosphere and hydrosphere, respectively. Continents and oceans lie on plates. During low tides, the level of ocean water goes down and the land below the water near the coast is exposed. Ships wreck when they strike against the rocks in the ocean. All the concepts which are important from the exam perspective are provided in these MSBSHSE Class 8 solutions of Social Science Geography Chapter 4. The topics covered in these solutions are a stepping stone to score well in the exam. The detailed step by step explanations provided for each question help students to solve the toughest problem in a shorter duration.

MSBSHSE Class 8 Social Science Geography Chapter 4 Objective Questions: Textbook Important Questions and Solutions

MSBSHSE Class 8 Social Science Geography Chapter 4 Textbook Exercise Questions

Q 1. Choose the correct option:

(a) Like there are landforms on land, ocean floor also has submerged landforms because ……

(i) There is land under water

(ii) There are volcanoes underwater

(iii) Land is continuous and there is water in deeper parts.

(iv) Though land is continuous, its level is not the same everywhere like that of water .

(b) Which part of the ocean floor is most useful to man ?

(i) Continental shelf

(ii) Continental slope

(iii) Abyssal plains

(iv) Marine deeps

(c) Which one of the following options is related to marine deposits?

(i) Rivers, glaciers, remains of plants and animals

(ii) Volcanic ash, continental shelf, remains of plants and animals

(iii) Volcanic ash, lava, fine particles of soil

(iv) Volcanic ash, remains of plants and animals, abyssal plains

Answer a: (iv) Though land is continuous, its level is not the same everywhere like that of water.

Answer b: (i) Continental shelf

Answer c: (iii) Volcanic ash, lava, fine particles of soil

Q 2. (a) Name the landforms shown in the figure.

(b) Which of these landforms is useful for deep sea research?

(c) Which of these are appropriate to be used for the protection of marine borders and naval-base building?

Answer a: 1 – Submerged Hill

2 – Marine Island

3 – Abyssal Plain

4 – Marine Trench

5 – Sea Level

6 – Continental Shelf

Answer b: Trenches, abyssal plains, etc are useful for deep sea research. On the ocean-bed, there are some landforms which are deep, narrow and steep. They are called marine deeps or trenches. Generally, the shallower ones are called marine deeps while deeper ones and extending for longer distance are called trenches. The mid-oceanic submerged hills and marine trenches are geologically the most active areas of the ocean-bed in the world. There are many active volcanoes here. These areas are also earthquake-prone areas.

Answer c: Islands are useful for protection of marine borders and naval-base building.

Q3. Give geographical reasons:

(a) The study of the ocean floor is useful to man.

(b) The continental shelf is a paradise for fishing activity.

(c) Some marine islands are actually the peaks of sea mountains.

(d) The continental slope is considered to be the boundary of continents.

(e) The disposal of waste materials in the oceans by man is harmful to the environment.

Answer a: Land submerged below oceanic water is called the ocean floor. The relief of ocean floor is decided upon by the depth from the seafloor and the shape of the land there. It has diverse landforms ranging from the continental shelf to trenches and mountains.The land near the coast and submerged under the sea is called continental shelf. For deep sea research, the study of the ocean floor is useful. The scientists, by determining the age of rocks, have developed plate tectonics theory which explains the formation of various landforms like mountains, trenches, and activities like volcanoes and earthquakes.

Answer b: The land near the coast and submerged under the sea is called continental shelf. This is the shallowest part of the ocean bed. It is also called submerged coastland. Its slope is gentle. The extent of the continental shelf is not uniform everywhere. It is narrow along the coasts of some continents while it is broad for hundreds of kilometers at others. Its depth is upto 200 meters below sea level. The continental shelf is very important from the human point of view. Extensive fishing grounds are found in the continental shelf. As this part is shallow, the sunlight reaches its bed. Algae, plankton, etc. grow here. This is food for fish.

Answer c: The hills and mountains found on the ocean-bed are called submerged hills and mountains. These hills are hundreds of kilometers wide and thousands of kilometers long. Peaks of some of the submerged hills come above the sea level. They are visible to us as marine islands. Iceland in the Atlantic Ocean, Andaman and Nicobar Islands in the Bay of Bengal are examples.

Answer d: After the extent of continental shelf is over, the slope of the sea bed becomes steeper. This is called continental slope. The depth of the slope is from 200 m to 3600 metres. In some places, it is more. The continental slope is narrow. The lower boundary of continental slope is considered to be the boundary of continents.

Answer e: In oceans, human-induced material are also found. This includes sewage, solid waste, radio-active material, waste chemicals, plastics, etc. These wastes prove hazardous to the hydrosphere. These materials are extremely harmful to marine life and its environment. Though the polluting components are less, their nuisance value is more.

Q 4. Observe the map on Pg 27 in ‘Give it a try’ and answer the following questions:

(a) Madagascar and Sri Lanka are related to which landform of the ocean floor?

(b) Near which continent are these landforms located?

(c) Which islands in our country are examples of peaks of submerged mountains?

Answer a: Madagascar and Sri Lanka are related to Marine Islands.

Answer b: Sri Lanka is located near Asia and Madagascar near the African continent.

Answer c: Andaman and Nicobar Islands are considered to be emergent peaks of a submerged mountain range related to the Arakan Yoma range of Myanmar.