Geomorphological Processes In Deserts Flashcards
What is weathering?
The breaking down or decaying of material where it is (in situ)
What is chemical weathering?
Where rock breaks down through the addition of chemicals
What is an example of chemical weathering?
Carbonation
What is mechanical weathering?
Where rock breaks down into smaller fragments but no chemical change
What is biological weathering?
A combination of chemical and mechanical weathering involving animals and plants
What is mass movement?
The movement of material down a slope due to gravity
What is saltation?
Smaller particles bounce along the bed
What is traction?
Large particles in water roll or slide along the bottom
What is suspension?
Even finer grains do not touch the bed
What is Solution?
Material is dissolved (In water only)
What is abrasion?
Where the Earth’s surface is worn away by the material being dragged across it
What is attrition?
When rocks knock against each other. Break each other down into smaller and rounded rocks
What does capacity mean in terms of deserts?
How much sediment can be carried by a particular process
What reduces the capacity of the wind or water currents?
Any loss of energy
Why is biological weathering much more important in the past?
Since there was evidence of it happening
What is thermal fracturing?
During the day, rocks expand when its hot and contract at night when its cold.
What do thermal expansion and contraction occurring at different rates and different parts of the rock lead to?
Fractures
What is salt weathering caused by?
Saline (salty) water
Where does saline water come from?
Rainfall or groundwater that’s drawn up by evaporation
What does the saline water do to cause salt crystals to form?
Enters pores or cracks and the high temperature causes the water to evaporate and form salt crystals
What happens in salt weathering as the crystals form?
They expand and put pressure on the rocks
What happens as more evaporation occurs to the salt crystals?
Expand even more and causes pieces to fall off due to pressure
Where does freeze-thaw weathering/frost shattering occur?
In areas where there is moisture and temperature that fluctuates above and below freezing
What is freeze-thaw weathering/frost shattering?
When water from rainfall enters the joints and cracks in rock
What happens at night for freeze-thaw weathering/frost shattering?
Temp drops and water freezes and expands
What happens as freeze-thaw weathering/frost shattering occurs over time?
Weakens the rocks causing pieces to fall off
What are 3 forms of chemical weathering?
Hydration
oxidation
Carbonation
What is hydration in terms of chemical weathering?
When moisture combines with minerals in rocks
What happens when the moisture combines with the minerals in rocks?
This causes them to swell which puts pressure on rocks and this causes pieces to crack off.
What is oxidation in terms of chemical weathering?
When rocks containing iron are exposed to oxygen in air or water.
What happens when rocks containing iron are exposed to oxygen?
Forms iron oxide which is weak and causes the rock to crumble easily
What is carbonation in terms of chemical weathering?
When CO2 in the atmosphere dissolves in rainwater forming a weak carbonic acid.
What happens when CO2 dissolves into rainwater forming a weak carbonic acid?
This acid reacts with the rocks that contain calcium carbonate so the rocks are gradually dissolved.
