WEATHERING

Weathering of the slope above the river can occur in four main ways. After weathering the load may fall into the river and be transported away.

Freeze Thaw

(Occurs in cold climates, where temperatures fluctuate above and below freezing point)

• Water gets in cracks and joints of rocks.
• this water freezes, expanding as ice
• the expansion causes the rock tto expand, and crack more
• When ice thaws,a nd more moisture gets into the crack
• Process is repeated many times, until the rock is broken away.

Exfoliation

(After repetative heating and cooling layers of rock crack off, like onion skins. Some moisture is usually presant.)

• Dark granite accepts heat readily.
• Outside of the rock is heated more than the inside.
• Due to this heating the outer layer of rock expands.
• Because the outer layer is expanding and the inner layer is not the rocks outer layer cracks.
• After many heatings and coolings the outer layer cracks off.

Chemical

(Acid from rain causes granular dissintegration)

• Granite is particularly susceptible to this form.
• Acid reacts with its crystaline structure readily.

Biological

(Plants break down and leave acid deposits which chemically weather rock. Physical break down of rocks by roots is not a major factor.)

• Basically chemical weathering, acid is from humus from decomposing plant material.

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