RATES OF WEATHERI

NGLesson 6

Rates of weathering The speed at which rock are broken down.

This depends on several factors:ClimateRock CharactericsVegetation

CLIMATEChemical Weathering Physical Weathering

Most intense in hot and wet climate

Chemical reactions promotes by high temperatures

Heavy rainfall provides necessary moisture for the processes

E.g: Deep weathering profile and typical red soil in tropical climate reflect active oxidation

Particularly active in cold climates where frost shattering dominates

Also active in desert climates where insolation weathering or exfoliation dominates

Climatic conditions 1. Strong Chemical Weathering – Hot and

wet Temperature: 70C – 300C Rainfall : 1600 – 2500mm

2. Weak Chemical Weathering Temperature: -30C to -200C Rainfall : 0 – 900mm

3. Strong Physical Weathering Temperature: -50C to -100C Rainfall : 300 mm to 1300mm

4. Weak Physical Weathering Temperature: 00C to 90C Rainfall : 0 – 1700mm

Rock CharacteristicsDefine the term joints

and bedding planes.

Joints – fractures or cracks that run through rocks

Bedding planes – the junctions between

beds of sedimentary rocks

Permeability and porosityWhich of the following texture is easily

weathered?

VegetationPresence of vegetation promotes

weathering

Organic acids speed up hydrolysis

Moss cling to rock surface, holding water against them like a wet sponge encourage chemical weathering

At the same time protect a rock surface from temperature extreme which reduce physical weathering