Important Questions: Landforms & their Evolution | Geography Class 11 - Humanities/Arts PDF Download

Very Short Answer Type Questions

Q1: What is the relief?
Ans: The physical landscape of the earth’s surface is called relief. It includes mountains, valleys, plains, and plateaus.

Q2: Arrange the following from smaller to bigger form: stream, gully, river, rill.
Ans: Rill, gully, stream, river.

Q3: What do you understand by mud-flow?
Ans: Mud-flow is a moving mass of solid waste fluid by rain or melting snow.

Q4: What is a landform?
Ans: The landform is the shape, focus and volume of a specific physical feature of the earth’s surface produced by natural processes of erosion and deposition.

Q5: Name two basic forms in which the running water acts as a geomorphic agent.
Ans: As a geomorphic agent, the running water acts in two basic forms, namely overland flow and channel or streamflow.

Q6: What are three closely inter-related geomorphic works performed by rivers?
Ans: Rivers perform three closely inter-related geomorphic works, viz., erosion, transportation, and deposition.

Q7: What is Karst topography?
Ans: Karst topography is a landscape formed by groundwater in a limestond region.

Q8: Why is wind action most prominent in arid and semi-arid areas?
Ans: Wind action is most prominent in arid and semi-arid areas as there are loose particles of soil in these areas and wind can remove them easily.

Short Answer Type Questions

Q9: What are snowfields? Where are they generally situated?
Ans: The vast areas which are permanently covered with snow and ice are called snowfields.
The snowfields are generally found situated above the snow line.

• High latitudes and polar regions,
• Near mountain tops.

Q10: Write a short note on the formation of sand dunes.
Ans: Wind deposits sand brought by it as sand dunes. The major features of these sand dunes are as follows:

• A sand dune is a typical hill. It has a crest.
• It is generally mobile as it goes on shifting along the direction of the prevailing wind.
• Obstructions in the path of the wind lead to the formation of the sand dunes.
• Sand dunes vary in size. They vary from a few metres to 300 metres in height.

Q11: What is a fiord?
Ans: When a glacial trough formed near the sea gets filled up by the seawater, it is called a fiord. Thus a fiord is a deep, steep-sided water inlet near the sea. It is typical of Norwegian and Chilean coasts.

Q12: Define fluvial denudation.
Ans: Running water is undoubtedly the most important agent of denudation. It is most conspicuous as a stream or river that transports enormous volumes of surplus precipitation from the land to the ocean. Stream action, in combination with weathering, mass wasting and overland flow, is responsible for the total process called fluvial denudation.

Q13: Discuss the features developed due to falling rain on bare surfaces.
Ans: Gentle rain falling on bare surfaces loosens the soil and muddies the water. The muddy water flows as the thin, slow-moving surface layer of water called sheet flow. As the slope increases, the water scours additional sediments and erodes small channels, which are called rills. Headward erosion of rills and their subsequent widening leads to gully formation. Gullies dissect the land into a number of isolated hills, giving rise to badland topography.

Long Answer Type Questions

Q14: Write an essay on the geomorphic work of rivers,
Ans: Rivers are the stream channels organised into branching channel network. Rivers perform three closely interacted geomorphic works, viz.,

• erosion,
• transportation,
• deposition. River erosion is the progressive removal of minerals from the surface of stream channel which itself may consist of the bedrock of regolith. River transportation is the movement of eroded particles in a chemical solution, in turbulent suspension or 6y rolling and changing along the bed. River deposition consists of -accumulation of any transported particles on the stream bed on the adjoining flood plain or on the floor of a body of standing water into which the river empties. While the river performs all three functions simultaneously, one may dominate over the other in different parts of the river course.

The nature of river erosion depends upon the materials of which the channel is composed. Erosion is hydraulic action, the pressure and drag of flowing water exerted upon grains projecting from the bed and banks. Weak bedrock and various forms of regolith are easily carved out by hydraulic action. Abrasion occurs when rock particles carried in the current strike against the exposed bedrock of the channel. Small particles are reduced by crushing and grinding when caught between larger cobbles and boulders. The chemical reaction between ions carried in solution and exposed mineral surfaces result in a form of erosion called a solution.

Q15: Which is the most important agent modifying the coastal topography? Describe the various features formed by this agent of gradation.
Ans: The most important agent modifying coastal topography is sea waves. Sea waves erode, transport and deposit debris in the coastal regions and form both erosional as well as depositional features,
Erosional Features: Arches and Sea stacks: If the rock formation along the coast differs in resistance, softer rocks are eroded and harder remain to stand. This results in the formation of arches and stacks.

Depositional Features:

• Sea waves deposit sand, gravel and pebbles on the shore. These deposits are called beaches. Marine beach (Triplicane) in Chennai is famous in India.
• Sometimes sea waves deposit embankments of sand and gravel on the seafloor not far from the coast. These embankments are termed as bars. Very often ships strike against these bars and cause damage to themselves.
• Sometimes sand bars separate a portion of the sea from the main sea, giving birth to a lake lagoon. A lagoon is a saltwater .lake. These lakes have a connection with the main sea through sand and gravel along with the narrow outlets. Malabar coast in India abounds in lagoons. On the eastern coast, Chilka (in Orissa) and Pullicat (near Chennai) are two well-known lagoons.

Q16: Discuss features created by wave action.
Ans: At the shoreline, the line along which the water meets the land, the major erosive agent is wave action. Along the coast of hard rock, a gently inclined rock surface is carved out to accommodate the swash and backwash. It is called abrasion platform. A shoreline rising abruptly from the abrasion platform is called a marine cliff. The stormy waves thrust rock fragments with great violence against the cliff base to develop wave-cut notches or sea-caves. Relatively thick and gently sloping accumulation of sand, gravel or cobbles in the zone of breakers and surf is called beads.

Q17: How does wind affect rocks and what kinds of rocks are eroded the fastest? Explain the formation of landforms by winds.
Ans: Winds are not strong enough to remove the mineral matter from hard rocks, moist clay or soil rich in vegetation. They can only affect those rocks which are soft, arid and vegetation less. Hence rocks which are soft are eroded the fastest.

• Formation of landforms by winds: Winds form landforms both during erosional and depositional work.
• Erosional landforms: Winds erode loose particles of soil and take them away. In course of a time, a hollow is formed in the desert surface. This is called a wind-eroded basin.
• Depositional landforms: When the wind becomes weak and some obstacle lies in its path, deposition of transported loose particles begin to take place. Wind becomes weak due to the decrease in its velocity. As a result of the depositions, sand dunes are formed. They are of different types and shapes.

Q18: Distinguish between:
(i) V-shaped valley and U-shaped valley.
Ans: V-shaped valley: V-shaped valleys are typically found in areas with fast-flowing rivers and streams. They are characterized by steep, narrow sides and a narrow bottom. V-shaped valleys are formed primarily by the erosive action of running water, cutting down into the landscape over time.
U-shaped valley: U-shaped valleys, also known as glacial valleys, are formed by glaciers. They have a characteristic U shape, with steep sides and a broad, flat bottom. Glaciers, as they move, erode the landscape, carving out these U-shaped valleys. The distinctive U shape is a result of the grinding action of the glacier as it moves, scraping and shaping the valley floor and walls.

(ii) Valley glacier and Continental glacier.
Ans: Valley glacier: Valley glaciers are glaciers that form in mountainous regions and flow down valleys. They are long, narrow glaciers that move downhill through valleys, shaping the landscape as they go. Valley glaciers are typically found in high-altitude areas and are often surrounded by mountains.

Continental glacier: Continental glaciers, also known as ice sheets, are vast ice masses that cover large areas of continents. Unlike valley glaciers, which are confined to valleys, continental glaciers spread out horizontally, covering vast portions of the land beneath them. The most well-known examples of continental glaciers are the ice sheets in Antarctica and Greenland.

(iii) Gorge and Canyon.
Ans: Gorge: A gorge is a narrow, steep-sided valley with a river or stream flowing through it. Gorges are often characterized by cliffs or high, rocky walls. They are typically formed by the erosive action of rivers cutting through rock over millions of years. Gorges can be deep and dramatic, creating stunning natural landscapes.
Canyon: A canyon is a deep, narrow valley with steep sides, often with a river or stream flowing through the bottom. Canyons are broader than gorges and are usually the result of various geological processes, including erosion by rivers, wind, or glaciers. Canyons can vary widely in size, from small and picturesque to large and grand, such as the Grand Canyon in the United States.

Q19: Discuss the internal and external forces involved in the creation of landforms.
Ans: Landforms on Earth's surface are the result of a combination of internal and external forces acting over geological time scales. These forces shape the landscape through various processes. Let's explore the internal and external forces involved in the creation of landforms:

Internal Forces

1. Tectonic Forces:

• Plate Tectonics: The movement and interaction of Earth's lithospheric plates lead to the creation of various landforms. When plates collide, they can form mountain ranges (e.g., Himalayas). When they pull apart, they create rift valleys (e.g., East African Rift). Subduction zones, where one plate is forced beneath another, lead to the formation of deep ocean trenches and volcanic arcs.
• Earthquakes: Sudden movements along faults due to tectonic forces can cause earthquakes, which can create fault lines and influence the topography.
• Volcanism: The eruption of molten rock (magma) onto the Earth's surface leads to the formation of volcanoes and volcanic landscapes. Over time, repeated volcanic activity can build mountains and alter the land significantly.

2. Endogenic Processes:

• Diastrophism: Diastrophism refers to the deformation of Earth's crust, leading to the creation of various landforms. This can occur through processes like folding, faulting, and uplift.
• Volcanism: The eruption of lava and ash from volcanoes creates new landforms, including mountains, lava plateaus, and volcanic islands.

External Forces:

1. Erosion:

• Water Erosion: Rivers, streams, and rainfall erode the land, creating features such as valleys, canyons, and river deltas. Water also transports sediments, reshaping landscapes.
• Wind Erosion: Wind can erode softer rocks and create features like sand dunes and rock pedestals in deserts and arid regions.
• Glacial Erosion: Glaciers, massive sheets of ice, erode the land by plucking and abrasion. Glacial erosion forms U-shaped valleys, fjords, and other distinctive features.

2. Deposition:

• River Deposition: When rivers slow down, they deposit sediments, forming features such as riverbanks, floodplains, and alluvial fans.
• Glacial Deposition: Melting glaciers deposit sediments, creating landforms like moraines, drumlins, and eskers.
• Wind Deposition: Wind can deposit sand and dust, forming dunes, sandbars, and loess deposits.

3. Weathering:

• Physical Weathering: Processes like freeze-thaw cycles, pressure release, and abrasion break down rocks into smaller particles, contributing to the formation of soil and sediments.
• Chemical Weathering: Chemical reactions dissolve minerals in rocks, altering their composition. Acid rain, water, and organic acids are common agents of chemical weathering.

4. Biological Activity:

• Plant Roots: Plant roots can break apart rocks, contributing to physical weathering. Plants also produce organic acids, enhancing chemical weathering.
• Burrowing Organisms: Animals like earthworms and insects burrow into the soil, aiding in the mixing of organic material and minerals, promoting soil development.

Q20: What is ‘regolith’?
Ans: Regolith refers to the layer of loose, fragmented material that covers solid rock on the Earth's surface, the Moon, Mars, and other celestial bodies. It is essentially the layer of unconsolidated material, including soil, dust, small rocks, and mineral fragments, that sits above bedrock. Regolith forms as a result of weathering processes such as erosion, chemical weathering, and mechanical breakdown of rocks. On Earth, regolith includes soil, which is the upper layer that supports plant life, and subsoil, which is the layer beneath the topsoil. Regolith is vital for terrestrial ecosystems as it provides the medium for plant growth and supports various forms of life.
On celestial bodies like the Moon, Mars, and asteroids, regolith consists of fine dust, small rocks, and larger boulders. Lunar regolith, for example, was created by meteorite impacts and the grinding action of micrometeoroids over billions of years. Astronauts on the Moon found it challenging to walk on the lunar regolith because it lacks the compactness and stability of Earth's soil. Understanding regolith is essential for space exploration, especially for planning lunar or Martian habitats and mining resources. The properties of regolith can influence the design of spacecraft, landers, and habitats, as well as strategies for extracting resources in extraterrestrial environments.