Class 11 Geography (Fundamental of Physical Geography) Chapter 6 Landforms and the Evolution

Key Concept: Basic Definition

b) An irregular surface with sharp pinnacles, grooves, and ridges

[Solution Description] Lapies are defined as irregular surfaces with sharp pinnacles, grooves, and ridges. This characteristic is due to differential solution activity along joints in limestone regions.

Key Concept: Erosion and Deposition

c) Creation of river valleys and floodplains

[Solution Description] Running water, as a geomorphic agent in humid regions, causes both erosion and deposition. Over time, it leads to the formation of various landforms due to these processes. The erosional activity forms gorges or valleys, while deposition results in features like river terraces or alluvial fans.

Key Concept: Feature Identification

a) Sea stacks

[Solution Description] Sea stacks are formations that result from the process of coastal erosion where parts of cliffs have been eroded away, leaving behind isolated columns of rock.

Key Concept: Integrated Concept Application, Real-world Application

d) Increase in beach size due to reduced wave energy

[Solution Description]

The presence of an artificial offshore bar will reduce the wave energy reaching the beach, leading to more deposition and less erosion. This typically results in an increase in the size of the beach as sediments accumulate.

Key Concept: Karst Topography

c) Sinkholes

[Solution Description] Karst topography is characterized by features formed due to the dissolution of soluble rocks like limestone, resulting in specific structures such as sinkholes.

Key Concept: Erosional Landforms

c) Steep rock face along the coastline

[Solution Description] A cliff is characterized by its steep face, usually formed as a result of continuous erosion by waves at the base causing material to collapse.

Key Concept: Location Identification

b) On the concave side of meanders

[Solution Description] Point bars, also known as meander bars, are typically found on the concave side of meanders. They form due to sediment deposition in these areas where the water velocity is lower.

Key Concept: Glacial Erosion

d) U-shaped

[Solution Description] Glacial valleys are typically U-shaped due to the erosive action of glaciers which carve through the landscape, creating broad floors and steep sides.

Key Concept: Delta Growth

b) It results in clear layers with coarser materials at the bottom and finer ones on top.

[Solution Description] Stratification in delta deposits refers to the arrangement of sediment layers that are formed as the river carries different sizes and types of materials over time. The heavier and coarser materials settle first, while lighter and finer particles settle later. Over time, this leads to a well-defined layering effect.

Key Concept: Basic Definition

c) A landform created by deposition of sediment by rivers at the base of mountain slopes

[Solution Description] An alluvial fan is a landform created by the deposition of sediments from streams when they flow from higher elevations to lower-lying foot slope plains.

Key Concept: Complex Processes, Interaction of Forces

b) Erosion increases drastically due to enhanced wave energy at high tide

[Solution Description]

During strong storms, high-energy waves significantly affect beaches. When combined with spring tides, which have higher tidal ranges, the potential for erosion increases. Shingle beaches, composed of pebbles and cobbles, are more resistant than sandy beaches but can still be reshaped by such forces. The energy from the waves during a storm can cause accretion or removal of materials depending on existing conditions.

Initially, let’s consider the interaction between storm waves and shingle beaches:

– Storm waves carry more energy and are capable of moving larger sediments compared to regular waves.

– At spring tide, water levels are at their highest, exposing areas that are usually not subjected to wave action.

As a result of simultaneous storm waves and spring tides, increased erosion occurs as high-energy waves impact and displace the material on the upper part of the shingle beach. The correct answer is “Erosion increases drastically due to enhanced wave energy at high tide.”

Key Concept: Location Identification

c) Glacial mountains

[Solution Description] According to the syllabus, outwash plains are found at the foot of glacial mountains or beyond continental ice sheets.

Key Concept: Erosional Features

c) Sea Stack

[Solution Description] Sea stacks are formed as a result of the erosion of headlands when waves erode the softer parts of the rock, leaving behind isolated columns or pillars.

Key Concept: Feature Recognition

b) An inselberg

[Solution Description] As mountains reduce and form a pediplain, inselbergs are often left behind as remnants of the original mountainous relief.

Key Concept: Example Identification

b) Mount Everest

[Solution Description] The Matterhorn is a well-known example of a horn, characterized by its high, sharp pointed and steep sides, located in the Alps.

Key Concept: Geomorphic Agents

b) Wind

[Solution Description]

Sand dunes are formed through the processes of wind action, specifically by the transportation and deposition of sand particles carried by wind. Therefore, wind is the primary geomorphic agent responsible for the creation of sand dunes.

Key Concept: Dune Stability

d) Vegetation cover

[Solution Description] Vegetation cover acts as a binding agent and helps trap sand, preventing it from being blown away by the wind, thus stabilizing the dune.

Key Concept: Characteristics Identification

a) Triangular facets

[Solution Description] Hanging valleys often have triangular facets, which are steep, triangular-shaped slopes that form along their walls. These features are created by the erosive action of smaller tributary glaciers.

Key Concept: Basic Features

b) U-shaped

[Solution Description] Glacial valleys are typically U-shaped. This shape is formed due to the movement and erosive action of glaciers, which carve out broad floors and steep sides as they move through mountainous regions.

Key Concept: Detailed Process

b) Rotation of pebbles and boulders by flowing water

[Solution Description] Potholes grow in size primarily through the continuous process of abrasion. Water carrying pebbles and boulders rotates these fragments inside the depressions, grinding the rock surfaces and enlarging the pothole progressively.

Key Concept: Valley Types

b) Canyon

[Solution Description] A canyon is a deep valley with very steep sides, often forming step-like structures due to geological processes like river cutting through rock layers over time.

Key Concept: Delta Growth

b) They increase in length

[Solution Description] As deltas grow over time, the deposition of sediments causes changes in the landscape. River distributaries increase in length as they branch out to distribute water and sediment across the expanding delta plain.

Key Concept: Simple Comparison

a) Landscapes are larger than landforms

[Solution Description] Landscapes consist of several related landforms, forming large tracts of the earth’s surface, whereas landforms are smaller individual features.

Key Concept: Sand Dunes

b) Consistent wind direction

[Solution Description] Sand dunes form primarily in deserts through wind deposition; consistent wind direction is crucial for their formation and shaping.

Key Concept: Simple Processes

b) Solution

[Solution Description] The primary process responsible for the formation of caves in limestone regions is the solution process, where water dissolves calcium carbonate present in limestone, leading to cave formation.

Key Concept: Comparative Analysis

b) Cirques form at glacier heads; horns form as isolated peaks

[Solution Description] A cirque is a large basin with steep walls formed by glacial erosion, generally located at the head of a glacier. On the other hand, a horn is a sharp mountain peak formed through the headward erosion of multiple cirques surrounding it.

Key Concept: Erosional Feature

a) Cirque

[Solution Description]

A cirque is a bowl-shaped erosional feature formed at the head of a glacier valley through processes such as plucking and abrasion. It is typically surrounded by steep cliffs.

Key Concept: Basic Definitions

b) Landforms are physical features like valleys; landscapes include both physical features and human modifications.

[Solution Description] Landforms are individual natural features of the earth such as mountains or valleys, while landscapes refer to larger areas that include multiple landforms and other elements like vegetation.

Key Concept: Process Identification

c) Erosion by wind

[Solution Description]

In arid environments, wind is a major geomorphic agent responsible for landform formation due to the lack of vegetation and moisture that allows wind to easily erode and deposit materials.

Key Concept: Definition Recall

c) A large depression formed by joining sinkholes and dolines

[Solution Description] A uvala is a large, closed depression formed by the merging of several sinkholes and dolines in karst terrain.

Key Concept: Characteristics

b) Tunnels

[Solution Description] Continued wind erosion of deflation hollows can lead them to develop into caves, as the wind removes more material, potentially creating underground voids or tunnels.

Key Concept: Comparative Analysis

c) Beaches are formed by sediment deposition from waves; sand dunes by wind deposition behind beaches

[Solution Description] Beaches are formed by sediment deposition from rivers and wave erosion, while sand dunes are formed by wind deposition behind the beaches.

Key Concept: Wave-Cut Platforms

d) Retreat of the cliff due to wave erosion

[Solution Description] A wave-cut platform indicates a retreating coastline where erosion by waves has flattened an area at the base of a sea cliff, showing past levels of wave activity.

Key Concept: Formation Conditions

b) Strong wind currents

[Solution Description] Mushroom rocks are primarily formed by wind deflation and abrasion, which means strong wind currents are necessary to carry out these processes effectively.

Key Concept: Formation Process

c) Rapid vertical erosion

[Solution Description] The formation of incised meanders is primarily attributed to rapid vertical erosion. This occurs when a stream cuts downwards into its bed at a faster rate, often leading to deep and narrow channels characteristic of hard rock terrains.

Key Concept: Landform Types

d) Canyon

[Solution Description] A canyon is a deep gorge, typically one with a river flowing through it, characterized by steep, step-like side slopes. The other options do not fit this description.

Key Concept: Valley Type Recognition

d) V-shaped valley

[Solution Description] Shallow V-shaped valleys with no or narrow floodplains are typical characteristics of valleys formed during the youth stage of river development. In this stage, the vertical erosion is dominant, leading to the formation of such valleys.

Key Concept: Coast Types

c) Erosional

[Solution Description] High rocky coasts typically have strong wave action that erodes the landscape, creating erosional features such as cliffs and wave-cut platforms.

Key Concept: Formation Process

b) When a stalactite and stalagmite meet

[Solution Description] A pillar in a cave is formed when a stalactite from the ceiling and a stalagmite rising from the floor meet and fuse together. This formation results from continuous deposition of calcium carbonate over time.

Key Concept: Landform Evolution

a) Youth

[Solution Description]

The youth stage of landform evolution is marked by the presence of V-shaped valleys. This occurs when a landscape has been subjected to substantial erosion but has not yet developed wide floodplains or meandering paths.

Key Concept: Basic Concepts

c) A small to medium tract of earth’s surface

[Solution Description] A landform is defined as a small to medium tract of the earth’s surface, which could include features like hills, valleys, plateaus, and plains.

Key Concept: Formation Processes

c) Delta

[Solution Description]

The major coastal features formed by river-borne sediments include deltas. These form when the sediment load carried by a river is deposited as it enters a slower-moving or standing body of water like an ocean, sea, or lake.

Key Concept: Basic Measurement

c) 1 km

[Solution Description] Drumlins can measure up to 1 km in length, as they are elongated formations created through glacial activity.

Key Concept: Cause and Effect

b) Creation of sand dunes

[Solution Description] Wind action behind beaches leads to the transportation and accumulation of sand, ultimately resulting in the formation of sand dunes. As wind carries beach sand inland, it accumulates in mounds when natural obstacles slow down the wind speed, facilitating sand deposition.

Key Concept: Basic Definition

c) A loop-like channel pattern

[Solution Description] A meander is a loop-like channel pattern that develops over flood and delta plains, characterized by its winding curves.

Key Concept: Shape and Structure

d) Horse-shoe

[Solution Description] Terminal moraines often form in a horse-shoe shape, creating long ridges of debris deposited at the end of glaciers.

Key Concept: Basic Process Understanding

c) It shapes coastal landforms through erosion and deposition

[Solution Description] Wave action plays a critical role in shaping coastal landforms through processes such as erosion and deposition. Waves can erode rocky coasts and deposit sediments to form features like spits and bars.

Key Concept: Agent Identification

c) Wind

[Solution Description] Geomorphic agents include natural forces such as running water, wind, glaciers, groundwater, and waves, all of which can cause erosion and deposition affecting landforms.

Key Concept: Basic Differences

d) U-shaped

[Solution Description] Glacial valleys are typically U-shaped because glaciers carve out broad, deep troughs as they move through an area, unlike river valleys which tend to be V-shaped.

Key Concept: Basic Features

c) Oxbow lakes

[Solution Description] In the old stage of a river, the common features include meanders, oxbow lakes, and natural levees due to the gentle gradient and lateral erosion.

Key Concept: Seasonal Changes

c) Monsoon

[Solution Description] Playas are most likely to transform significantly during the monsoon as this is the period when these desert basins can collect considerable amounts of water due to increased precipitation. However, they dry up once the rainfall ceases due to high evaporation rates.

Key Concept: Karst Features

c) Lapies

[Solution Description] Lapies are ridges that form on limestone surfaces due to uneven chemical weathering or solution activity, where some parts dissolve faster than others.

Key Concept: Predictive Analysis, Advanced Reasoning

b) Increased risk of structural damage and possible collapse of existing infrastructure

[Solution Description] An increasing number of sinkholes indicates active subsurface erosion processes due to the continuous dissolution of limestone or other soluble rocks. This can destabilize the ground, posing significant risks to existing infrastructure such as roads, bridges, and buildings, potentially leading to structural failure. Future planning should consider reinforcing foundations and monitoring land stability. Moreover, areas prone to sinkhole formation may require restrictions on new construction to avoid damage.

Key Concept: Depositional Features

d) Barchans

[Solution Description] Barchans are crescent-shaped sand dunes that have their horns pointing downwind. They form as a result of wind depositing sand on the leeward side.

Key Concept: Material Composition

b) Coarse materials like boulders and blocks

[Solution Description] Eskers consist of very coarse materials like boulders and blocks, along with minor rock debris.

Key Concept: Meander Development

b) Mature

[Solution Description] During the mature stage of a stream, trunk stream meanders are typically confined within the valley.