Worksheet Solutions: Landforms and their Evolution | Geography Class 11 - Humanities/Arts PDF Download

Fill in the Blanks

Q1: Small to medium tracts or parcels of the earth’s surface are called _______.
Ans: Landforms
Landforms refer to natural features on the Earth's surface, such as mountains, valleys, plains, and hills. They can vary in size and shape.

Q2: The science of landforms is known as _______.
Ans: Geomorphology
Geomorphology is a branch of geology that focuses on the study of landforms, their origin, evolution, and the processes that shape them.

Q3: Landforms change their shape due to changes in _______.
Ans: Climate
Changes in climate, including temperature, precipitation, and weather patterns, can influence processes like erosion and deposition, leading to alterations in landform shapes over time.

Q4: Groundwater contributes to landform evolution primarily through the process of _______.
Ans: Solution and precipitation deposition
Groundwater can dissolve certain types of rock, like limestone, through chemical processes known as solution. When this water re-emerges in caves or underground spaces, it can deposit minerals, creating various landforms like stalactites and stalagmites.

Q5: Valleys start as small and narrow _______.
Ans: Rills
Rills are small and narrow channels that initially form on the land's surface due to the flow of water. Over time, these rills can grow and deepen, developing into valleys.

Q6: Potholes and plunge pools form over the rocky beds of _______.
Ans: Rock beds of hill-streams
Potholes and plunge pools are erosional landforms created when flowing water, often in hill-streams or rivers, erodes the rocky riverbed. These features deepen over time due to the action of water and rock fragments.

Q7: Sinkholes are commonly found in areas with _______.
Ans: Limestone/karst areas
Sinkholes are depressions or holes in the ground that typically form in areas with soluble rocks like limestone. They develop as the limestone dissolves due to the action of groundwater.

Q8: Caves in limestone areas are primarily formed due to _______.
Ans: Chemical process of solution and precipitation deposition
Caves in limestone areas result from the dissolution of calcium carbonate in the rock by slightly acidic groundwater. As water seeps through the rock, it dissolves the limestone, creating hollow spaces. When the water evaporates, it leaves behind mineral deposits in the form of stalactites and stalagmites.

Q9: Stalactites hang like icicles and are made of _______.
Ans: Calcium carbonate
Stalactites are formations that hang from the ceilings of caves. They are composed of calcium carbonate, which is deposited when water carrying it in solution drips from the cave roof and loses carbon dioxide.

Q10: Glaciers move primarily due to the force of _______.
Ans: Gravity
Glaciers are large masses of ice that move slowly over land surfaces. Their movement is driven by the gravitational force, as ice flows downhill due to its weight and pressure.

Assertion and Reason Based

Q1: Assertion: Landforms are the result of various geomorphic processes.
Reason: Geomorphic processes include the action of agents like running water, glaciers, wind, and more.
(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) Assertion is true, but Reason is false.
(d) Assertion is false, but Reason is true.
Ans: (a)
The Assertion correctly states that landforms are the result of various geomorphic processes, which include the action of agents like running water, glaciers, wind, and more. The Reason also aligns with this by further explaining the nature of these geomorphic processes and how they contribute to the formation of landforms. Therefore, Reason is the correct explanation for the Assertion.

Q2: Assertion: Overland flow can lead to the formation of sheet erosion.
Reason: Sheet erosion occurs when water flows over irregular land surfaces.
(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) Assertion is true, but Reason is false.
(d) Assertion is false, but Reason is true.
Ans: (a)
The Assertion is accurate as overland flow can lead to the formation of sheet erosion. The Reason provides a correct explanation, stating that sheet erosion occurs when water flows over irregular land surfaces. It clarifies the cause-and-effect relationship between overland flow and sheet erosion, making it the correct explanation for the Assertion.

Q3: Assertion: Meanders are a type of landform.
Reason: Meanders are formed due to the propensity of water to work laterally on banks and coriolis force.
(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) Assertion is true, but Reason is false.
(d) Assertion is false, but Reason is true.
Ans: (a)
Meanders are indeed a type of landform, and the Reason accurately describes their formation by mentioning the propensity of water to work laterally on banks and the influence of the Coriolis force. The Reason provides a valid explanation for the formation of meanders, making it the correct explanation for the Assertion.

Q4: Assertion: Stalactites and stalagmites are depositional forms in limestone caves.
Reason: They are formed due to the deposition of calcium carbonate when water carrying it in solution evaporates.
(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) Assertion is true, but Reason is false.
(d) Assertion is false, but Reason is true.
Ans: (a)
Stalactites and stalagmites are indeed depositional forms in limestone caves, primarily formed due to the deposition of calcium carbonate when water carrying it in solution evaporates. The Reason correctly explains the process of their formation, aligning with the Assertion and providing a valid explanation.

Q5: Assertion: Glaciers can cause significant damage to the landscape.
Reason: The movement of glaciers results in tremendous erosion due to friction caused by the weight of ice.
(a) Both Assertion and Reason are true, and Reason is the correct explanation of Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation of Assertion.
(c) Assertion is true, but Reason is false.
(d) Assertion is false, but Reason is true.
Ans: (a)
The Assertion is accurate as glaciers can cause significant damage to the landscape. The Reason provides the correct explanation by stating that the movement of glaciers results in tremendous erosion due to the friction caused by the weight of ice. This explanation clarifies the cause-and-effect relationship between glacier movement and landscape damage, making it the correct explanation for the Assertion.

Very Short Answer Type Questions

Q1: What are landforms?
Ans: Landforms are natural features on the surface of the earth created by various geological processes.

Q2: Name one primary geomorphic agent responsible for land surface degradation in regions with high humidity and heavy rainfall.
Ans: Running water.

Q3: Define overland flow and its role in landform evolution.
Ans: Overland flow is the spreading of water in a sheet over the land surface. It causes sheet erosion and is significant in the early stages of landform evolution.

Q4: What is a peneplain, and how is it formed?
Ans: A peneplain is an almost flat plain formed as a result of stream erosion, where narrow to wide paths of overland flow gradually develop into gullies and valleys, ultimately creating a lowland with faint relief.

Q5: Describe the characteristics of landscapes in the "Youth" stage in running water regimes.
Ans: In the "Youth" stage, streams are few with shallow V-shaped valleys, broad stream divides with marshes, swamps, and lakes, and the possible development of meanders on broad upland surfaces.

Q6: What are the main types of valleys that can be recognized in landforms?
Ans: V-shaped valleys, gorges, canyons, etc.

Q7: Explain how plunge pools are formed and their role in landform development.
Ans: Plunge pools are formed over rocky stream beds due to stream erosion and abrasion. They deepen and widen the valleys and help in the development of landforms.

Q8: What are incised or entrenched meanders, and where are they commonly found?
Ans: Incised or entrenched meanders are deep meanders cut into hard rocks and are typically found in streams flowing rapidly over steep gradients.

Q9: Define river terraces and explain their formation.
Ans: River terraces are surfaces marking old valley floor or floodplain levels. They form due to vertical erosion by the stream into its own depositional floodplain.

Q10: Name two depositional landforms created by running water.
Ans: Alluvial fans and deltas.

Short Answer Type Questions

Q1: Explain the stages of landscape development by running water.
Ans: The stages of landscape development by running water are as follows:

• Erosion: Running water erodes the land by wearing away the surface rocks and carrying away the eroded material.
• Transportation: The eroded material is transported by the running water through the process of suspension, saltation, and traction.
• Deposition: When the velocity of the water decreases, it can no longer carry the eroded material, leading to its deposition and the formation of new landforms.
  
  

Q2: Describe the formation of point bars in meandering rivers.
Ans: Point bars are formed on the inside of a meander bend in a river. As the river flows around the bend, the velocity of the water decreases, causing sediment to be deposited on the inside of the bend. Over time, this deposition builds up and forms a point bar.

Q3: How are river terraces formed, and what are paired terraces?
Ans: River terraces are formed when a river undergoes downcutting, eroding its channel and leaving behind elevated floodplains. Paired terraces refer to two terraces on opposite sides of a river channel, formed during different stages of downcutting.

Q4: What are the differences between canyons and gorges in terms of their characteristics?
Ans: Canyons and gorges are both deep, narrow valleys, but they have some differences. Canyons are typically formed by the erosive action of rivers, while gorges can be formed by other processes like tectonic activity. Canyons often have steep sides and may have a river flowing through them, while gorges can have more gradual slopes and may not always have water bodies within them.

Q5: Discuss the role of groundwater in the development of landforms, focusing on karst topography.
Ans: Groundwater plays a significant role in the development of landforms, particularly in karst topography. Karst topography is characterized by soluble rocks such as limestone, which can be dissolved by groundwater over time. As groundwater flows through fractures and joints in the limestone, it creates cavities and enlarges existing ones, leading to the formation of features like sinkholes, caves, and underground drainage systems.

Q6: Explain the formation of caves in limestone areas.
Ans: Caves in limestone areas are formed through a process called speleogenesis. Rainwater, which is slightly acidic, absorbs carbon dioxide from the atmosphere and forms a weak carbonic acid. As this acidic water infiltrates the limestone, it reacts with the calcium carbonate present in the rock, causing it to dissolve. Over time, the dissolution of limestone creates void spaces that develop into caves.

Q7: Discuss the role of glaciers in the erosion of landforms.
Ans: Glaciers play a significant role in the erosion of landforms through two main processes: plucking and abrasion. Plucking occurs when glaciers freeze onto rocks and pluck them away as the glacier moves. Abrasion, on the other hand, involves the scraping and grinding action of the rocks embedded in the glacier on the underlying bedrock. These processes contribute to the formation of landforms such as cirques, U-shaped valleys, and fjords.

Q8: Describe the process of deposition in deltas and its impact on landforms.
Ans: Deposition in deltas occurs when a river carrying sediments reaches a body of water, such as an ocean or a lake. As the river's velocity decreases upon entering the standing body of water, it can no longer carry the sediments, resulting in their deposition. This deposition of sediments leads to the formation of landforms such as natural levees, distributaries, and delta plains. These landforms can significantly impact the local geography and create fertile soil for agriculture.

Long Answer Type Questions

Q1: Describe the formation of valleys and their types, including V-shaped valleys, gorges, and canyons.
Ans: Valleys start as small rills that gradually develop into gullies, which further deepen, widen, and lengthen to become valleys. Depending on dimensions and rock types, various valley types like V-shaped valleys, gorges, and canyons can be recognized. A gorge is characterized by steep, straight sides, while a canyon has step-like slopes and is wider at the top than at the bottom. The type of valley formed depends on the rock type and structure. Canyons commonly form in horizontal bedded sedimentary rocks, while gorges develop in hard rocks.

Q2: Explain the formation of caves in limestone-rich regions and their various types, including tunnels.
Ans: Caves are prominent in areas with alternating rock beds, with limestone or dolomite layers in between or in regions with dense, massive limestone beds. Water percolates down through the materials or along cracks, dissolving the limestone along bedding planes. Long and narrow to wide gaps called caves result from this dissolution. Caves can have various elevations based on the limestone beds and intervening rocks, and some caves have openings at both ends, known as tunnels.

Q3: Describe the formation and characteristics of stalactites, stalagmites, and pillars in limestone caves.
Ans: Stalactites are icicle-like formations that hang from the cave roof, with broad bases tapering toward the free ends. Stalactites form when water carrying calcium carbonate in solution drips and deposits the mineral as it loses carbon dioxide. Stalagmites rise from the cave floor, forming directly below stalactites. They can take the shape of columns or discs with rounded or crater-like ends. Over time, stalactites and stalagmites can fuse to create columns and pillars of various diameters. These formations are typical in limestone caves and add to the unique beauty of cave environments.

Q4: Explain the role of glaciers in the creation and transformation of landforms, emphasizing the processes of erosion and deposition.
Ans: Glaciers are masses of ice that move over land as sheets or in trough-like valleys. Their slow movement is primarily due to the force of gravity. Glaciers are significant agents of erosion and can cause substantial changes in the landscape. As glaciers move, they pluck and drag large angular blocks and fragments from the land, causing abrasion and plucking. This process can reduce high mountains into low hills and plains.
Glaciers erode unweathered rocks and can create deep valleys and fjords. The material they transport, known as glacial till, is deposited when the glacier melts or retreats. The deposited materials can form landforms like moraines, outwash plains, and kettle holes. The action of glaciers can dramatically reshape landscapes and leave behind evidence of their presence for future generations.