INDIAN SCHOOL MUSCAT MIDDLE SECTION DEPARTMENT OF SOCIAL SCIENCE THE CHANGING FACE OF THE EARTH. Name: Class VII Sec Roll. No: Date:.02.

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1 INDIAN SCHOOL MUSCAT MIDDLE SECTION DEPARTMENT OF SOCIAL SCIENCE THE CHANGING FACE OF THE EARTH Name: Class VII Sec Roll. No: Date: I NAME THE FOLLOWING 1) The forces that arise from inside the Earth. 2) The forces which are active on the surface of the Earth. 3) The theory of explanation about the changing face of the Earth. 4) Broken pieces of lithosphere. or 5) The tectonic plates floats on this semi molten rocks of the lower mantle. 6) The heat from the core sets off these disturbances in the mantle. 7) The tectonic plates that move towards each other. 8) The tectonic plates that move away from each other. 9) Two tectonic plates push against each other, the land at the point of contact raises to form these mountains. 10) These cracks or fractures are developed when rocks are compressed beyond a point. 11) The mountains formed when land between two fault lines is pushed up. 12) The valleys formed when land subsides between two fault lines 13) The vibrations that move through the surface of the Earth. 14) The enormous amount of energy released in the form of waves by the Earth due the sudden movements. or 15) The point where the earthquake disturbance originates in the interior of the Earth 16) The point that lies perpendicular to the seismic focus on the surface of the Earth 17) The instrument used to detect and record the intensity of the earthquake. 18) The opening on the surface of the Earth through which molten magma is poured out. 19) The activity of throwing out rocks and gases from the interior of the Earth. 20) The material released during volcanism. 21) The magma that spills out on the surface of the Earth. 22) The pool of magma inside the Earth. 23) The opening at the top of the volcanic mountain. 1

2 24) Two active volcanoes those that have erupted recently in the Mediterranean Sea. and 25) An excellent example of dormant volcano. 26) An extinct volcano in Tanzania. 27) The lakes formed by filling of water on the crater of extinct volcano. 28) The big loops along the river flow. 29) Fine grained river deposit. 30) The valleys formed when river cuts out narrow valley with steep walls. 31) The valleys formed when the river is young and flows very rapidly. 32) The mouth of the river roughly in a triangular shape. 33) Hills of sand formed by the deposits of wind. 34) The crescent shaped sand dunes. 35) Arm chair like depression formed by the erosive action of glaciers. 36) Sand wall or snow covered mountain tract formed by glacial deposition. II FILL IN THE BLANKS WITH APPROPRIATE WORDS: 1. The process sea erosion is called erosion. 2. When ice melts the cirque becomes a lake called 3. When fine sand particles are deposited over large areas they form 4. are slow moving rivers of ice. 5. A sand wall like deposits on a snow-covered mountainous tract are called 6. The valleys formed by the glaciers are 7. Gradational process involves, and 8. A river becomes larger when it is joined by. 9. Earthquakes under the sea can cause 10. Sometimes molten magma pours out through a series of long cracks called III. FILL IN THE BLANKS WITH SUITABLE FEATURES FORMED BY THE FOLLOWING AGENTS OF GRADATION: NO GRADATIONAL AGENT 1 RIVER DEPOSITIONAL FEATURE EROSIONAL FEATURE 2 WIND 2

3 3 WAVE 4 GLACIER 1V. ANSWER THE FOLOWING IN ONE POINT: 1. What is a Volcano? A volcano is an opening in the Earth's crust through which molten rock and gases erupt from deep inside the Earth. 2. What are Earthquakes? Earthquakes are vibrations that move through the Earth and over its surface. They are caused by disturbances that originate from inside the Earth. 3. What is a plunge pool? When the water falls on the surface with great force, it erodes the rock material beneath, creating a depression called a plunge pool. 4. What is weathering? Weathering is the breaking up the rock material on the surface of the Earth due to exposure to the atmosphere. 5. What are levees? The raised banks of the river flowing through the flood plain are called levees. 6. What are tributaries? The river breaks into number of channels as it moves through the sandbars is called distributaries. 7. What is a delta? A delta is a more or less triangular alluvial tract formed by the sediments deposited by tributaries as the river enters the sea. 8. What are sea caves? When strong waves break and erode the rock materials along the coast, hollow caves called sea caves are formed. 9. What are stacks? When the roof of the sea arches break completely due to excessive erosion, pillar- like features left behind are called stacks. 10. What are sea cliffs? Vertical steep rock faces along the shore are called sea cliffs. 11. How are wave-cut platforms formed? When sea cliffs are eroded, they collapse and move backwards, leading to the formation of wave-cut platforms. 3

4 12. How are beaches formed? Beaches are formed when sea deposits eroded materials like pebbles, sand and boulders along the coast. V ANSWER THE FOLLOWING IN TWO POINTS: 13. What are earthquakes? How are they caused? Earthquakes are vibrations that move through the Earth and over its surface. They are caused by the disturbances that originate inside the Earth. 14. What are Seismic waves? How do these waves cause earthquake? Sudden movements deep beneath the surface, like the rupture of rocks and collision of tectonic plates, release enormous amount of energy in the form of seismic or shock waves. These seismic waves travel to the surface and cause earthquake. 15. What does the theory of plate tectonics state? The Theory of Plate Tectonics was put forward by the scientists to explain the changing face of the Earth. According to this theory, the lithosphere is broken up into number of pieces called tectonic/ lithospheric plates. These rigid plates float on semi-molten rocks of the lower portion of the upper mantle. 16. Distinguish between convergent and divergent plates. Tectonic plates that move towards each other are called convergent plates. Tectonic plates that move away from each other are called divergent plates. 17. How an ox-bow lake is formed? The river swings from side to side as it flows over a level tract, forming winding sections and loops. Continuous erosion on the concave side and deposition on the convex side can cut a loop from the main river and lead to the formation of an ox-bow lake. VI. ANSWER THE FOLLOWING IN FOUR POINTS: 18. How are Block Mountains formed? Explain. When rocks are compressed beyond a point, they develop cracks or fractures called faults. Sometimes faults develop due to forces of tension, i.e.; when plates are pulled apart. Land gets along the fault lines. When land is pushed up between two fault lines, Block Mountains are formed. 19. Explain the upper course of the river. The river usually starts as a stream. It flows fast down steep slopes. Erosion is the main activity of the river at this stage. The river forms I-shaped valleys or steep gorges and V-shaped valleys in this stage. 4

5 20. Explain the activity of wind which leads to the formation of mushroom rocks. Strong winds blow in desert areas, picking up the sand particles. When sand-laden winds blows against rock face, the particles hit the rock with great force. The base of the rock is eroded vigorously from all sides by the suspended sharp dust particles in the lower layer of the winds. This leads to a broad top and a narrow bottom forming a mushroom rock. ************************************************** 5