UNIT III

THE HYDROSPHEREAND

GRADATIONAL PROCESSES

• the origin and development of landform features is attributed to the work of wind, waves, ice

Geomorphology: formal scientific study of landforms, the study of form or shape of Earth’s surface

Landforms (landscape features) are a product of interaction among three primary factors:

1. Structure2. Process3. Development

1. Structure

a) Geological Structure

• arrangement of rock components acquired during process of formation or deformation (e.g. folds and faults)

• gradation occurs along zones of weakness

b) Rock Type (Lithology)

• physical, chemical properties of Earth’s materials

• different rock types exhibit varying

degrees of susceptibility to weathering

and erosion

E.g. granite/rhyolite/dolomite are more resistant than limestone/ sandstone/shales

Dolomite

Limestone

2. Process• there are three principal agents of landscape formation or agents of change:

WATER, ICE, and WIND

• of these, by far the most important in terms of the amount of gradation achieved and the proportion of Earth’s land surface area is WATER (even in glacial and desert environments)

Landscape reduction is accomplished by three processes:

a) Weathering• the mechanical and

chemical break-up of Earth’s materials into smaller particles. Also, there is Biological weathering.

b) Erosion• involves the pick-up

and transportation of weathered materials from one location to another

Weathering

Erosion

c) Deposition

• involves the accumulation of transported earth materials (debris) in localities where energy is no longer available for work and transport

• occurs on level surfaces, still water bodies or surfaces of zero potential energy – known as base level of erosion

3. Stage of Development

• the type and rate of geomorphological evolution is also a function of the nature and intensity of the stresses imposed by various agents of weathering and erosion, as well as, the length of time

Geographical Cycle: theory of landscape evolution which says landscapes tend to evolve through three distinct stages of development from the time they are first subjected to the time they are totally consumed by agents of weathering and erosion

Stage 1: Youth

V-Shaped Valley

Stage 2: MaturityIntegrated system of streams, and valleys, sharp divides

Stage 3: Old AgeCharacterized by the development of a plain of subdued relief

Homework

1. Read Chapter 7, “Wearing Down the Land fro Above” pp. 102- 108.

2. Answer question 1 on p. 114.

3. Explain the difference between mechanical and chemical weathering. Be sure to be able to provide examples.

4. Answer question 3 on p. 114.