Class 11 Geography (Fundamental Of Physical Geography) Chapter 5 Geomorphic Processes

Key Concept: Cause and Effect

c) Variations in geothermal gradients and heat flow

[Solution Description] Variations in geothermal gradients and heat flow within the Earth lead to the movement and pressure changes that cause unevenness on the Earth’s crust.

Key Concept: Basic Definition

b) Weathering

[Solution Description] Soil formation begins with weathering, which breaks down rocks into smaller particles and provides the basic materials for soil development.

Key Concept: Process Comparison

c) Soil creep occurs gradually, while solifluction involves saturated soils over impermeable surfaces.

[Solution Description] Soil creep is the gradual downhill movement of soil and rock, which occurs over a long period with minimal visible change. Solifluction involves slow, water-saturated soil flow over impermeable surfaces, typically more active when thawing occurs.

Key Concept: Energy Dynamics

b) Loss of energy

[Solution Description]

Deposition occurs when erosional agents lose energy, leading to the settling of materials. As the energy diminishes, the ability of the agent to carry debris reduces, resulting in the deposition of sediment.

Key Concept: Geothermal Gradient Effects, Advanced Process Analysis

b) Epeirogenic movements causing broad uplifts or depressions

[Solution Description]

Variations in geothermal gradients can lead to uneven heating of the lithosphere, which affects processes like epeirogeny. Epeirogeny refers to the gentle up or down warping of large areas of the Earth’s crust. This process is often driven by thermal expansion or contraction resulting from changes in geothermal gradients. Such differential heating can lead to broad regional uplift or subsidence as different parts of the crust respond variably to the internal heat flux.

Key Concept: Time Factor

a) Time allows for the accumulation of organic material and nutrient cycling.

Time allows for the accumulation of organic material and nutrient cycling.

Key Concept: Agent Recognition

a) Water

[Solution Description] Geomorphic agents are natural forces that contribute to the shaping of Earth’s landscape. In exogenic processes, common agents include water, wind, ice, and waves which erode, transport, and deposit materials on Earth’s surface.

Key Concept: Basic Definition

b) A dome-shaped rock formation resulting from unloading and thermal expansion

[Solution Description] An exfoliation dome is a smooth, rounded rock formation resulting from the flaking off of curved sheets of rock.

Key Concept: Types of Movements

c) Slump

[Solution Description] A slump is characterized by the downward slipping of a mass of rock or unconsolidated material moving as a unit along a curved surface.

Key Concept: Basic Factors

d) Erosion

[Solution Description] The five basic factors controlling soil formation are parent material, topography, climate, biological activity, and time. Erosion is not listed among these factors.

Key Concept: Geomorphic Agents

c) Running water

[Solution Description] Running water is the primary geomorphic agent responsible for sediment transport in river systems by acquiring, transporting, and depositing rock debris.

Key Concept: Basic Concepts

b) Radioactivity

[Solution Description] The main energy sources for endogenic processes are radioactivity, rotational and tidal friction, and primordial heat. These internal energy sources drive various geological processes within the Earth.

Key Concept: Forces Identification

c) Volcanism

[Solution Description] Endogenic forces originate within the Earth and include activities such as volcanism which involves magma from beneath the Earth’s crust reaching its surface.

Key Concept: Basic Concepts

c) Gravity

[Solution Description] Mass movements are mainly driven by gravity, which acts to move materials downslope.

Key Concept: Basic Definition

b) Movement of molten rock

[Solution Description] Volcanism involves the movement of molten rock (magma) onto or toward the earth’s surface as per the definition provided in the syllabus.

Key Concept: Process Mechanism

b) By causing expansion due to reduced pressure

[Solution Description] Pressure release, also known as unloading, contributes to physical weathering by reducing the pressure on rocks that are buried deep within the earth when overlying materials are eroded away. This reduction in pressure causes the rock to expand and crack into sheets or layers, a process often leading to exfoliation.

Key Concept: Basic Definition

d) Time

[Solution Description] The five basic factors controlling soil formation are parent material, topography, climate, biological activity, and time. Among these, all except “wind” are factors.

Key Concept: Basic Definition

c) Weathering mantle

[Solution Description]

The process of soil formation, also known as pedogenesis, begins with weathering. Weathering mantle acts as the fundamental layer that provides minerals and materials necessary for further soil development.

Key Concept: Process Effects

c) Orogeny

[Solution Description] Mountain building is primarily a result of endogenic processes, specifically orogenic movements which are part of diastrophism. These processes are driven by forces from within the earth, such as plate tectonics.

Key Concept: Basic Definition

a) Weathering

[Solution Description] Denudation refers to the stripping off or uncovering of earth materials, which includes processes like weathering, mass wasting, erosion, and transportation.

Key Concept: Energy Sources

c) Radioactivity

[Solution Description] Radioactivity is a major source of energy for endogenic processes. It contributes to heating within the Earth through radioactive decay.

Key Concept: Geothermal Gradients and Heat Flow

c) It increases the intensity of diastrophism

[Solution Description] An increase in geothermal gradients causes higher temperatures at various depths, which can lead to increased rock plasticity. This enhances the movement of tectonic plates and increases diastrophic activities such as folding and faulting.

Key Concept: Deposition Process

b) Velocity

[Solution Description] When erosional agents lose velocity and energy, they deposit the materials they are carrying, with coarser materials settling first.

Key Concept: Terminology

d) Epeirogeny

[Solution Description] Epeirogeny refers to the broad, relatively gentle vertical movements of large parts of the earth’s crust, resulting in uplift or subsidence without significant folding or faulting. This process contrasts with orogeny, which involves more intense deformation like folding and faulting.

Key Concept: Organism Contribution

c) Earthworms

[Solution Description] Earthworms, through their burrowing activities, can physically disturb soil and rock material. This activity helps in exposing new rock surfaces to chemical weathering processes by creating spaces between rocks. Among the given options, earthworms are more commonly associated with significant mechanical disturbance or wedging.

Key Concept: Process Dynamics

c) Desert due to diurnal temperature changes

[Solution Description] Physical weathering is most effective when temperature fluctuations are high, causing repeated expansion and contraction of rocks which leads to their breakdown. Deserts typically experience large temperature differences between day and night.

Key Concept: Basic Definition

c) Mechanical disintegration and chemical decomposition of rocks

[Solution Description] Weathering is the mechanical disintegration and chemical decomposition of rocks through the actions of various elements of weather and climate.

Key Concept: Role of Temperature

b) Through thermal expansion and contraction

[Solution Description] Temperature influences geomorphic processes through thermal expansion and contraction. As temperatures fluctuate, materials in rocks expand when heated and contract when cooled, which can cause fractures and contribute to weathering processes.

Key Concept: Deposition vs Erosion

d) Deposition increases surface height whereas erosion decreases it.

[Solution Description] Deposition is directly related to erosion as it occurs when erosional agents lose velocity and energy, causing carried materials to settle. Hence, deposition is a consequence of erosion.

Key Concept: Agent Recognition

a) Running water

[Solution Description] Geomorphic agents are natural forces or elements that contribute to the sculpting of Earth’s surface. Running water is one such agent as it plays a significant role in erosion, transportation, and deposition processes.

Key Concept: Basic Definition

b) Epeirogeny

[Solution Description] The process that involves uplift or warping of large portions of the earth’s crust is known as epeirogeny.

Key Concept: Comparative Analysis

d) Alluvial fans form at mountain bases, while deltas form at river mouths.

[Solution Description] Alluvial fans are formed when water slows down at the base of mountains, spreading sediments in fan shapes due to loss of energy. Deltas form where rivers meet larger bodies of water, depositing sediments as the river’s velocity decreases.

Key Concept: Basic Definition

b) Continent building

[Solution Description] Epeirogenic processes primarily cause the uplift or warping of large portions of the earth’s crust, which contributes to continent building.

Key Concept: Role of Kinetic Energy

b) Kinetic energy

[Solution Description] The syllabus states that denudational processes such as erosion and transportation are controlled by kinetic energy.

Key Concept: Soil Salts

c) Hardpan

[Solution Description] In dry climates, evaporation exceeds precipitation leading to the accumulation of salts on the soil surface, resulting in hardpan formation.

Key Concept: Basic Concepts

d) Energy from within the earth

[Solution Description] Endogenic processes are primarily driven by energy from within the earth, such as radioactivity, rotational and tidal friction, and primordial heat.

Key Concept: Process Effects

c) Volcanism

[Solution Description] At mid-ocean ridges, new oceanic crust is created through the process of seafloor spreading. This involves the upwelling of molten rock from below the Earth’s surface, which solidifies to form new crust as it cools. This process is a type of volcanism, where the molten material emerges and forms structures on the seafloor.

Key Concept: Energy Source

b) Geothermal gradients

[Solution Description] Endogenic processes like volcanism are driven by geothermal gradients and heat flow from within the earth. This internal heat is responsible for the movement of molten magma and subsequent volcanic activity.

Key Concept: Weathering and Biodiversity

b) By providing a variety of soil nutrients

[Solution Description] Weathering processes create soil through the breakdown of rocks, which provides a habitat for plant roots and microorganisms. In forests, this results in varied soil types that support diverse plant species, contributing to overall biodiversity.

Key Concept: Activating Causes

c) Earthquake activity

[Solution Description] Removal of vegetation can destabilize slopes by reducing root support and allowing for increased erosion, thus facilitating mass movements.

Key Concept: Basic Concepts

a) The Sun

[Solution Description] Exogenic processes are primarily driven by energy from the sun. Solar energy influences weather patterns and climatic conditions, which in turn affect geomorphic processes on Earth’s surface.

Key Concept: Geomorphic Agents

d) Wind

[Solution Description] Geomorphic agents such as water, wind, ice, and waves play roles in erosion, transportation, and deposition. Among them, wind is a significant agent contributing to these processes, especially in desert landscapes.

Key Concept: Exfoliation Basics

b) Flaking off of curved sheets from rocks

[Solution Description] Exfoliation refers to a physical weathering process where curved sheets or layers peel off from rocks, commonly due to factors like unloading and thermal expansion.

Key Concept: Simple Processes

b) Solidification of magma at the surface

[Solution Description] Extrusive volcanic landforms are created when magma reaches the earth’s surface and solidifies. This process requires the movement of magma towards the surface.

Key Concept: Basic Concepts

c) Radioactivity

[Solution Description] Endogenic processes are driven by internal energy sources within the Earth, such as radioactivity, rotational and tidal friction, and primordial heat. Among these, radioactivity is a significant source of energy.

Key Concept: Basic Forces

a) Gravitational force

[Solution Description] Physical weathering involves mechanical disintegration of rocks due to forces such as gravitational forces, expansion forces due to temperature changes, crystal growth, and water pressures.

Key Concept: Basic Concepts

c) Orogeny

[Solution Description] Orogeny is a diastrophic process that involves the formation of mountains due to severe folding and faulting of the Earth’s crust. It typically occurs at convergent plate boundaries.

Key Concept: Types of Movements

b) Creep

[Solution Description] The types of mass movements mentioned in the syllabus are creep, flow, slide, and fall. These involve the movement of rock debris down slopes under gravity.

Key Concept: Basic Concepts

c) Radioactivity

[Solution Description] The primary sources of energy for endogenic processes are radioactivity, primordial heat, and rotational and tidal friction. Among these, radioactivity plays a significant role in generating geothermal energy.

Key Concept: Biological Weathering Definition

b) Contribution to or removal of minerals and ions, and physical changes due to organisms

[Solution Description] Biological weathering involves the contribution to or removal of minerals and ions from the weathering environment, as well as physical changes due to organisms such as burrowing and wedging.

Key Concept: Basic Definition

b) Solution

[Solution Description] Solution, as a key process in chemical weathering, involves the dissolving of minerals within rocks by water.

Key Concept: Basic Definition

c) To create regolith and soils

[Solution Description] Weathering plays a crucial role in breaking down rocks into smaller particles, which contributes to soil formation and influences erosion processes. Hence, it is significant for creating regolith and soils.

Key Concept: Texture and Structure

d) Texture and structure

[Solution Description] Texture and structure of parent material determine how it breaks down and integrates with other soil components, influencing soil properties.

Key Concept: Category Classification

c) Rapid flow mass movements

[Solution Description] Mass movements are movements of soil, rock, or debris down a slope due to gravity. Landslides fall under the category of rapid flow mass movements because they occur quickly over a short period.

Key Concept: Basic Definition

c) Thermal expansion and contraction

[Solution Description] Granular disintegration primarily occurs due to physical forces like thermal expansion and contraction. These forces cause stress within rocks, leading to their breakdown into smaller particles.

Key Concept: Climatic Influence

b) Precipitation

[Solution Description] The process of erosion is significantly influenced by precipitation, as it leads to increased water flow which can carry away particles from the surface. Wind and temperature also influence erosion but are less direct compared to the effect of precipitation.

Key Concept: Organism Influence

d) Earthworms

[Solution Description] Earthworms contribute to biological weathering by burrowing into the soil, which helps expose new surfaces to air and water. This aids in chemical breakdown processes.

Key Concept: Process Identification

c) Carbonation

[Solution Description] Chemical weathering includes processes that chemically alter minerals like solution, carbonation, hydration, oxidation, and reduction; carbonation specifically involves the reaction of carbon dioxide with minerals.

Key Concept: Basic Definition

b) Movement of molten rock

[Solution Description] Volcanism involves the movement of molten rock, which refers to magma flowing onto or toward the earth’s surface.

Key Concept: Real-world Application

c) Owing to tectonically induced ground shaking

[Solution Description] Regions with active tectonics experience frequent earthquakes which can displace materials and destabilize slopes, making them prone to landslides. Additionally, tectonic activity can create fractures and faults that further weaken slope stability.

Key Concept: Reaction Conditions

c) Presence of heat

[Solution Description] Heat increases the rate of chemical reactions, making it a factor that accelerates chemical weathering processes. Higher temperatures result in faster decomposition and alteration of rocks.

Key Concept: Deposition Concept

c) Deposition

[Solution Description] When erosional agents lose their velocity, deposition occurs as mentioned in the syllabus.

Key Concept: Role of Gravity

c) Gravity

[Solution Description] Mass movements occur due to the transfer of rock debris down slopes under the influence of gravity. Thus, gravity is the primary force driving mass movements.

Key Concept: Climatic Influence

d) Glaciers

[Solution Description] Glaciers are highly sensitive to climatic conditions such as temperature and precipitation. Changes in these factors can lead to advances or retreats of glaciers, affecting their ability to erode and deposit materials.

Key Concept: Basic Concepts

c) Energy from within the Earth

[Solution Description]

Endogenic processes are driven by energy from within the earth, primarily due to factors like radioactivity, rotational and tidal friction, and primordial heat. This internal energy leads to various geological activities such as volcanic eruptions and mountain building.

Key Concept: Agent Recognition

b) Wind

[Solution Description] Geomorphic agents are natural elements that contribute to the shaping of Earth’s surface. These include water, wind, ice, waves, and currents. Among the options provided, “Wind” is a recognized geomorphic agent.