CBSE Class 7 Social Science Surface Landforms Change Assignment

Q. 1 Give suitable term to the following:
i) Different sections of the river.
Answer: Courses of a river (Upper course, middle course, and lower course)
In simple words: The stages through which a river flows from its source to its mouth.
Exam Tip: Remember the three distinct courses: upper, middle, and lower.

Q. 1 ii) Functions performed by the river.
Answer: Erosion, transportation, and deposition
In simple words: The three main geological works done by a river.

Exam Tip: List them in chronological order of river action.

Q. 1 iii) The river's most important action in the upper course.
Answer: Erosion
In simple words: Cutting down and wearing away rocks in the mountains.

Exam Tip: Erosion dominates the upper course due to steep slopes and high velocity.

Q. 1 iv) The valley which becomes deep and narrow, with steep, wall-like sides after being eroded by the river.
Answer: Gorge (or V-shaped valley)
In simple words: A deep, steep-sided valley carved by a fast-flowing mountain river.

Exam Tip: Deep gorges are also known as canyons when very large.

Q. 1 v) These are called large gorges.
Answer: Canyons
In simple words: Extremely deep and wide gorges, such as the Grand Canyon.

Exam Tip: Distinguish carefully between a standard gorge and a canyon.

Q. 1 vi) One feature formed when the river descends from a higher-level to a lower-level.
Answer: Waterfall
In simple words: Water plunging vertically down a steep drop in a river bed.
Exam Tip: Waterfalls are prominent features of the upper course of a river.

Q. 1 vii) Sediments deposited by river.
Answer: Alluvium
In simple words: Fine soil and silt carried and dropped by flowing water.

Exam Tip: Alluvium makes plains extremely fertile for agriculture.

Q. 1 viii) The bow-shaped lake.
Answer: Ox-bow lake
In simple words: A crescent-shaped lake formed when a meander is cut off from the main river.

Exam Tip: Frequently asked definition; mention the cutting off of meander loops.

Q.2 Fill in the blanks.
i) The s-shaped bends formed by the river are called as __________.
Answer: Meanders
In simple words: Large looping bends in the middle and lower course of a river.

Exam Tip: Do not confuse meanders with ox-bow lakes.

Q.2 ii) Deltas are formed at __________.
Answer: the mouth of a river (where it meets a sea or ocean)
In simple words: Triangular deposits of sediment at the end of a river.

Exam Tip: Mention both deposition and low tidal activity.

Q.2 iii) The rivers draining into __________ do not form deltas.
Answer: estuaries (or seas with strong currents/tides)
In simple words: Rivers that empty directly into the ocean without depositing sediment fans.

Exam Tip: Strong tidal action washes away sediments, preventing delta formation.

Q.2 iv) __________ is the largest delta in the world.
Answer: Ganga-Brahmaputra Delta (Sundarbans Delta)
In simple words: The massive delta formed by the Ganges and Brahmaputra rivers in India and Bangladesh.

Exam Tip: Note both the river names and the popular name Sundarbans.

Q.2 v) A pile of rocks deposited by glaciers is called __________.
Answer: Moraine
In simple words: Debris and rocks left behind by melting glaciers.

Exam Tip: Moraines can be terminal, lateral, or medial.

Q.2 vi) The action of wind is more prominent in __________ and __________.
Answer: deserts, arid regions (or dry regions)
In simple words: Places with little vegetation and strong winds experience high wind erosion and deposition.

Exam Tip: Sparse vegetation allows wind to easily pick up and move loose soil particles.

Q.2 vii) Mushroom rocks are features caused by the action of __________.
Answer: wind (wind erosion)
In simple words: Rocks shaped like mushrooms due to sandblasting near the ground by wind.

Exam Tip: Lower parts erode faster because wind carries more sand close to the ground.

Q.2 viii) The thickest loess deposits are found in __________.
Answer: China (North-Western China / Loess Plateau)
In simple words: Massive wind-blown dust deposits found notably in China.

Exam Tip: Loess is extremely fertile, fine-grained yellowish dust.

Q.3 Define the following.
i) Oasis
Answer: An oasis is a fertile spot in a desert where water is found, usually from an underground spring or water source, supporting vegetation and human settlement.
In simple words: A green watered area in the middle of a dry desert.

Exam Tip: Mention both water availability and vegetation growth.

Q.3 ii) Lagoon
Answer: A lagoon is a shallow body of salt or brackish water separated from a larger sea or ocean by a narrow sandbar, barrier island, or coral reef.
In simple words: A shallow coastal pool cut off from the open sea by sandbars.

Exam Tip: Chilika Lake in Odisha is a classic example of a coastal lagoon.

Q.3 iii) Delta
Answer: A delta is a fan-shaped or triangular deposit of alluvial sediments formed at the mouth of a river where it enters a standing body of water like a sea or lake.
In simple words: A triangular pile of mud and silt dropped at the river mouth.

Exam Tip: Highlight the triangular shape and depositional nature.

Q.4 Complete the following table.
Answer:

Exam Tip: Learn at least one specific real-world example for each erosional agent.

Q.5 Match the two columns-
Answer:
i) Estuaries - b) Do not involve transportation
ii) Glaciers - e) Moraines
iii) Wind - c) Mushroom rocks, sand dunes
iv) Weathering, Erosion, Mass movement - d) Denudation
v) Weathering - f) Humus (Note: weathering breaks rocks; biological weathering contributes to humus formation)
vi) Chilika - g) Largest lagoon (Orissa)
vii) Soil - a) Beaches and lagoons (Contextually matched per standard school key pairs)
In simple words: Matching geographical terms with their correct characteristics or landforms.

Exam Tip: Double-check matching pairs carefully to avoid stray mismatches.

Q. 6 Name and label the following diagrams.
1. Barchan (Crescent-shaped sand dune)
2. Coastal Landforms (Sea cliff, Sea cave, Stack, Arch)
Answer:
Diagram 1: Barchan (showing wind direction arrows and crescent horns pointing leeward).
Diagram 2: Coastal landforms showing Sea Cliff, Sea Cave, Sea Arch, Stack, and Stump.
In simple words: Identification of standard wind-blown dune and coastal erosion diagrams.
Exam Tip: Practice drawing simple outlines of barchans and sea arches with clear arrows.

Q.7 Draw the different sections of a River's Course and label its features.
Answer:
The river's course is divided into three main sections:
1. Upper Course (Source): Features V-shaped valleys, gorges, canyons, waterfalls, and rapids.
2. Middle Course: Features meanders, river valleys widening, and gentle slopes.
3. Lower Course (Mouth): Features floodplains, ox-bow lakes, levees, distributaries, and deltas.
In simple words: A sketch showing how a river changes from steep mountain streams to wide flat plains and deltas.
Exam Tip: Clearly label source, three courses, and mouth with distinct landforms for full marks.

Q.8 Answer the following questions.
i) What are the factors that influence the rates of weathering and erosion?
Answer: The rates of weathering and erosion are influenced by:
1. Climate (temperature and rainfall): High temperature and heavy rainfall accelerate chemical and mechanical weathering.
2. Rock type and structure: Soft rocks weather and erode much faster than hard rocks like granite.
3. Slope of the land: Steeper slopes lead to faster erosion due to high water velocity and gravity.
4. Vegetation cover: Plant roots bind soil and reduce erosion.
In simple words: Climate, rock hardness, land slope, and plant cover decide how fast rocks break and wear away.

Exam Tip: Bullet points are best for factors-based geography questions.

Q.8 ii) Describe the formation of a delta.
Answer: As a river reaches its lower course and enters a sea or lake, its speed decreases significantly. Due to the reduced velocity, the river deposits its heavy load of sediments (alluvium). When the river deposits sediment faster than the sea can remove it, the sediments accumulate and choke the river channel, forcing the river to split into smaller distributaries. This triangular deposition of sediment is called a delta.
In simple words: When a slow river drops its silt into the sea faster than waves wash it away, a triangular land called a delta is formed.

Exam Tip: Mention drop in river velocity, sediment deposition, and formation of distributaries.

Q.8 iii) How can we conserve soil?
Answer: Soil can be conserved through several methods:
1. Afforestation and Reforestation: Planting trees prevents soil erosion by binding soil particles with roots.
2. Terrace Farming: Cutting steps on hill slopes slows down water runoff.
3. Contour Ploughing: Ploughing across contours rather than up and down prevents water gullies.
4. Crop Rotation: Growing different crops sequentially maintains soil fertility.
5. Building check dams and windbreaks to stop wind and water erosion.
In simple words: Planting trees, farming along hill steps, and rotating crops protect soil from washing or blowing away.

Exam Tip: List at least 3 to 4 practical soil conservation measures.

Q.8 iv) Differentiate between weathering and erosion.
Answer:
1. Weathering is the static, in-situ breakdown of rocks into smaller fragments by physical, chemical, or biological agents without transporting them.
2. Erosion is the dynamic wearing away and transportation of weathered rock materials by agents like running water, wind, ice, and waves.
In simple words: Weathering breaks rocks where they sit; erosion carries the broken pieces away.

Exam Tip: Highlight "in-situ breakdown" vs "transportation" for a crisp distinction.

Q.9 Give reasons.
i) In an estuary no delta is formed.
Answer: An estuary receives strong tidal currents and wave action from the sea. These strong currents continuously wash away and sweep out all the sediments brought down by the river, preventing the accumulation of deposits necessary to form a delta.
In simple words: Strong sea waves wash away river silt before it can pile up into a delta.

Exam Tip: Emphasize the role of strong sea tides and currents.

Q.9 ii) The action of wind is more prominent in dry regions.
Answer: In dry (arid and semi-arid) regions, there is very little rainfall and sparse vegetation cover. The lack of plants and moisture leaves loose sand and soil exposed, making it easy for strong winds to pick up, transport, and deposit particles, thereby making wind a powerful erosional and depositional agent.
In simple words: Deserts have dry soil and no plants, so strong winds easily blow sand around.

Exam Tip: Mention sparse vegetation and lack of moisture as key reasons.