Chapter 6: Landforms And Their Evolution
Source: NCERT Official Textbook
The chapter provides a detailed, agent-wise breakdown. For running water in humid regions, it explains erosional features like valleys, gorges, potholes, and depositional forms such as alluvial fans, deltas, floodplains, and natural levees. It then covers groundwater processes, focusing on karst topography characterized by sinkholes, caves, stalactites, and stalagmites in limestone regions.
The work of glaciers is described, forming U-shaped valleys, cirques, horns, and depositing moraines, eskers, and drumlins. Coastal processes by waves create cliffs, stacks, spits, and bars along high rocky coasts, while building beaches and dunes on low sedimentary coasts.
Finally, in arid environments, wind acts as a dominant agent, eroding to form pediments, deflation hollows, and mushroom rocks, and depositing sorted materials as various types of sand dunes. The chapter emphasizes that the evolution of these landforms is a dynamic and continuous process.
Topics Covered:
Section A: Descriptive Questions
- What is a landform? How is it different from a landscape? (Pg. 1) Page 47
- Describe the three stages of landscape development (Youth, Mature, Old) in a running water regime. (Pg. 2) Page 48
- How are potholes formed by stream erosion? (Pg. 2-3) Page 48-49
- What are river terraces and how are they formed? (Pg. 3) Page 49
- Explain the difference between an active floodplain and an inactive floodplain. (Pg. 4) Page 50
- Explain why meanders develop over flood and delta plains. (Pg. 5) Page 51
- What is the difference between a solution sink and a collapse sink (doline)? (Pg. 6-7) Page 52-53
- Name and describe the two main depositional features found within limestone caves. (Pg. 7) Page 53
- What is a horn and how is it formed? Give an example. (Pg. 8) Page 54
- What are moraines? Name and describe three types. (Pg. 9-10) Page 55-56
- What is the primary difference between high rocky coasts and low sedimentary coasts? (Pg. 11-12) Page 57-58
- How does a spit form? (Pg. 12-13) Page 58-59
- Explain the formation of a pediplain through the parallel retreat of slopes. (Pg. 13-14) Page 59-60
- How does wind act as a sorting agent in forming depositional landforms? (Pg. 14) Page 60
Section B1: Objective MCQs
What is considered the most important geomorphic agent in degrading land surfaces in humid regions? (Pg. 1)
View Answer
Reference: NCERT Page 47
What is the plain formed as a result of stream erosion called? (Pg. 2)
View Answer
Reference: NCERT Page 48
What are the large, deep holes at the base of waterfalls called? (Pg. 3)
View Answer
Reference: NCERT Page 49
What are the broad, cone-shaped deposits formed when streams break into foot slope plains called? (Pg. 3-4)
View Answer
Reference: NCERT Page 49-50
What are the low, linear ridges of coarse deposits along the banks of large rivers called? (Pg. 5)
View Answer
Reference: NCERT Page 51
A limestone region showing typical landforms produced by groundwater action is called ______ topography. (Pg. 6)
View Answer
Reference: NCERT Page 52
What are long, narrow to wide trenches formed when sinkholes join together called? (Pg. 7)
View Answer
Reference: NCERT Page 53
What are masses of ice moving as sheets over land or down mountain valleys called? (Pg. 8)
View Answer
Reference: NCERT Page 54
Glaciated valleys are typically: (Pg. 9)
View Answer
Reference: NCERT Page 55
What are sinuous ridges of sand and gravel deposited by streams flowing beneath a glacier called? (Pg. 10)
View Answer
Reference: NCERT Page 56
What are remnant masses of rock, originally parts of a cliff, standing isolated off the shore called? (Pg. 12)
View Answer
Reference: NCERT Page 58
Which of the following is NOT a primary erosional action of wind? (Pg. 13)
View Answer
Reference: NCERT Page 59
Shallow lakes in desert basins that retain water only for a short duration are called: (Pg. 14)
View Answer
Reference: NCERT Page 60
Crescent-shaped dunes with points directed downwind are called: (Pg. 14-15)
View Answer
Reference: NCERT Page 60-61
(Exercise) In which stage of landform development is downward cutting most dominant? (Pg. 15)
View Answer
Reference: NCERT Page 61
(Exercise) A deep valley characterised by steep step-like side slopes is known as: (Pg. 15)
View Answer
Reference: NCERT Page 61
(Exercise) In which region is chemical weathering more dominant than mechanical? (Pg. 15)
View Answer
Reference: NCERT Page 61
(Exercise) Which sentence best defines ‘Lapies’? (Pg. 15)
View Answer
Reference: NCERT Page 61
(Exercise) A deep trough with very steep concave walls at its head is known as: (Pg. 15)
View Answer
Reference: NCERT Page 61
Section B2: Factual One-Liners
The two components of running water are overland flow as a sheet and linear flow as ______. (Pg. 1) Page 47
Reveal Answer
A deep valley with very steep to straight sides is called a ______. (Pg. 2) Page 48
Reveal Answer
Meanders cut into hard rocks are called ______ or entrenched meanders. (Pg. 3) Page 49
Reveal Answer
Unlike alluvial fans, the deposits making up ______ are very well sorted with clear stratification. (Pg. 4) Page 50
Reveal Answer
Deposits found on the concave side of meanders are called ______ or meander bars. (Pg. 5) Page 51
Reveal Answer
Small to medium round depressions on limestone surfaces formed by solution are called ______ holes. (Pg. 6) Page 52
Reveal Answer
The irregular limestone surface with sharp pinnacles and ridges is called ______. (Pg. 7) Page 53
Reveal Answer
The most common landform in glaciated mountains, a deep trough at the head of a glacier, is a ______. (Pg. 8) Page 54
Reveal Answer
Very deep glacial troughs filled with seawater are called ______. (Pg. 9) Page 55
Reveal Answer
Smooth, oval-shaped ridges composed of glacial till are called ______. (Pg. 10-11) Page 56-57
Reveal Answer
A ridge of sand and shingle lying parallel to the coast in the offshore zone is called an ______ bar. (Pg. 12) Page 58
Reveal Answer
Gently inclined rocky floors close to mountains in deserts are called ______. (Pg. 13) Page 59
Reveal Answer
Wind-carved rock remnants with a slender stalk and broad cap are called ______ rocks. (Pg. 14) Page 60
Reveal Answer
Long ridges of sand aligned parallel to the wind direction in areas of poor sand supply are ______ dunes. (Pg. 15) Page 61
Reveal Answer
(Exercise) What do incised meanders in rocks indicate? (Pg. 15) Page 61