Weathering + River Erosion Flashcards
Define weathering
Softening / weakening rock
Define Erosion
Movement of weathered material
What are the 4 types of weathering
Mechanical
Carbonation
Oxidation
Hydrolysis
Explain mechanical weathering (Exfoliation)
Rock heats up during the day - Expands
Rock cools down during the night - Contracts
Constant expansion and contraction causes rock to shatter
Exfoliation - Expansion and contraction where corners peel off
Explain carbonation (Acid Rain)
Dry Deposits: Pollution on surface combines with water to form carbonic acid which weakens the rock
Wet Deposits: Carbon dioxide combines with water in the air to form carbonic acid
Explain oxidation
Oxygen combines with metal and when they combine rusting occurs.
Explain hydrolysis
Water seeps into rocks and interacts with certain minerals. Causes the minerals to expand and then when the mineral dries, it contracts. This expansion and contraction causes the rock to weaken.
Clay shrinks when it dries and expands when it gets wet
What are the 3 types of stream channels
Rock Controlled Channel
Meandering
Braided Channel
List 4 characteristics of a rock controlled channel
Upper Coarse
Vertical Erosion
Friction and the river is steep
Rapids / waterfall / plunge pool (Hydraulic Force)
Where is the fastest flow in a meandering channel
The OUTER edge of a river
Where is the slip-off bank of a river
The inside of the meanders
What is the Thalweg
The fastest flowing channel of the meandering channel
Why is meandering slope important for farming
It is on the flood plain
Slip-off slope has fertile soil
Farmers try to avoid undercut and farm on the slip-off
Explain how a braided channel is formed
The perimeter of the river is increased and therefore so does friction. The increase in friction makes the river slower. Due to the river slowing down, it begins to deposit sand. The river has to flow around these sand banks formed from this sand.
What is it called when a braided channel flows into the sea
A Delta
