Chapter 15 : External Processes

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  • Topic: Soil, Geomorphology, Sedimentary rock
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CHAPTER 15 (external processes)
What is meant by denudation?
The overall effect of the disintegration, wearing away, and removal of rock material. Implies a lowering of continental surfaces.

The three stages in denudation are?
1.Weathering is the breaking down of rock into smaller components by atmospheric and biotic agencies. 2. Mass wasting involves the downslope movement of broken rock material due to gravity. 3.Erosion consists of more extensive and generally more distant removal of fragmented rock material.

Weathering involves the mechanical disintegration and/or chemical decomposition of rock, whether the rock is above or below ground…..depends on ‘openings' which fall into 5 types…what are they? (microscopic, joints, faults, lava vesicles, solution cavities)

Microscopic: tiny and numerous, responsible for extensive weathering. May consist of spaces between crystals of igneous or metamorphic rocks, pores between grains of sedimentary rocks, minute fractures within mineral grains of any rock.

Joints: cracks that develop as a result of stress, innumerable in most rock masses dividing the blocks into various sizes. Most important of all rock openings.
Faults: cracks in bedrock along which there is relative movement of the walls making up the crack. Individual or occur in small numbers.
Lava vesicles: holes of various sizes, develop in cooling lava when gas is unable to escape as the lava solidifies.
Solution cavities: holes formed in calcareous rocks as the soluble minerals are dissolved and carried away by percolating water.

What is the basic difference between joints and faults?
Faults are individual and occur in small numbers, joints are multitudinous. Also, they sometimes appear as major landscape features. Faults allow easy penetration of weathering agents into subsurface areas.

What are the weathering agents? (p. 427) they are mostly atmospheric-explain
Atmosphere, Temperature changes, water, biotic agents....
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