Geomorphological processes Flashcards
What is weathering?
The breakdown or disintegration of rock in situ by agents such as ice, salt, plant roots and acids.
What does weathering lead to?
The transportation/transfer of materials.
What are sub-ariel processes?
Processes that slowly break down the coastline, weaken the underlying rock and allow for sudden movement.
What is an example of negative feedback in weathering?
If removal of debris is slow and ineffective it leads to build up which reduces cliff exposure and prevents weathering to some extent.
What is an example of positive feedback in weathering?
If the rate of debris removal exceeds the rate of weathering and mass movement then there is an increased vulnerability of the rock and increased weathering.
What is mechanical weathering?
The break-up of rocks w/o any chemical changes taking place - physical constant movement.
What are the diff. types of mechanical weathering?
- Freeze thaw
- Salt crystallisation
- Wetting and drying
What is freeze-thaw?
When water gets into cracks in the rocks and then freezes as the temp. drops. Expands as it freezes causing cracks to widen. This process repeats forcing the rock to break away and collect at base of cliff as scree.
These rock fragments can be used by the sea for marine erosion.
What is salt crystallisation?
When sea water that was in a crack in the rock evaporates leaving behind salt crystals. These can grow over time exerting pressure on the rock and causing it to break.
What is wetting and drying?
Occurs because rocks rich in clay such as shale expand when they are wet and contract as they dry causing rocks to crack and break.
What is biological weathering?
The breakdown of rocks due to organic activity.
How do plants cause weathering?
Plant roots grow into small cracks in rock beneath the surface or in cliff face. Cracks widen as roots grow. Cause rock to break up.
How does bio weathering contribute to chemical weathering?
Water running thro decaying veg becomes acidic - increased chem. weathering.
How do animals contribute to bio weathering?
Birds like puffins and sand martins and mammals like rabbits can burrow into cliffs causing rocks to crack.
Marine organisms like piddocks can also burrow into the rock.
What is chemical weathering?
Involves a chemical reaction where salts may be dissolved or clay like deposit may be a result which is easilt eroded.
What are the diff. types of chem. weathering?
- Carbonation
- Oxidation
- Solution
What is carbonation?
When rainwater absorbs carbon dioxide from the air to form a weak carbonic acid. This reacts w/ calcium carbonate in rocks (limestone, chalk) and forms calcium bicarbonate which is easily dissolved. Cooler rainwater, more CO2 absorbed.
What is oxidation?
Reaction of rock minerals w/ oxygen to form a rusty powder. Leaves rocks more vulnerable to weathering.
What is solution?
The dissolving of rock minerals e.g. halite (rock salt)
What are marine processes?
Processes that operate along the coastline and are connected w/ the sea e.g. tides, waves, LSD
What is hydraulic action?
The sheer force of water as it crashes against the coastline. Air becomes trapped and compressed in cracks in the rock.
Leads to cavitation.
What is cavitation?
When water retreats compressed air expands weakening the cracks.
Bubbles formed in the water may implode under high pressure generating tiny jets of water which erode over time.
What is wave quarrying?
The action of waves breaking against unconsolidated material like sands and gravel. Waves scoop out loose material and carry it away as sediment.
What is corrasion?
When waves pick up sand and pebbles from the seabed and it is thrown at cliff face by waves. Slowly chips away at rock and smooths the surface.
