1. What is denudation? 2. What is the difference between weathering and erosion?
3. What is the most basic difference between mechanical and chemical weathering?
KEYWORDS
freeze-thaw action scree (talus)
exfoliation (onion peeling)
diurnal temperature range
salt crystallisation honeycomb
pressure release (unloading)
4. What is biological weathering? 5. How can rock type affect the rate at which weathering occurs?
6. List three other factors that affect the rate at which weathering occurs.
Mechanical Weathering Processes
Freeze-thaw action Example: Croagh Patrick, Co. Mayo
Freeze-thaw action commonly occurs in mountainous areas where temperatures fluctuate above and below the freezing point of water. Mountainous areas have high precipitation levels, mainly due to relief rainfall and snowfall. Water from the rain and melting snow gathers in the joints of rocks, where it freezes when temperatures drop below 0°C at night. As the water changes to ice, its volume expands approximately 9%, widening the joint in the rock. During the day, temperatures rise above 0°C, allowing the ice to melt and the water to go further into the rock. As freeze-thaw action repeats itself over time, the cracks in the rock increase in size until the rock eventually cracks along its joints. Sharp angular pieces of rock called scree break away and move down slope under the influence of gravity (Fig. 6.1).
A-Z
Freeze-thaw action: Also referred to as ‘frost action’ or ‘frost shattering’.
