L2: Weathering and Erosion Flashcards
4 types of river transport
Solution - minerals are dissolved in the water and carried along in the solution.
Suspension - fine light material is carried along in the water.
Saltation - small pebbles and stones are bounced along the river bed.
Traction - large boulders and rocks are rolled along the river bed.
What are the 4 types of river erosion?
Hydraulic action - This is the sheer power of the water as it smashes against the river banks. Air becomes trapped in the cracks of the river bank and bed, and causes the rock to break apart.
Abrasion/Corrasion - When pebbles grind along the river bank and bed in a sand-papering effect.
Attrition - When rocks that the river is carrying knock against each other. They break apart to become smaller and more rounded.
Solution/Corrosion - When the water dissolves certain types of rocks, eg limestone.
2 types of wind erosion
Sandblasting or Wind Abrasion - Process in which rocks are eroded by particles of sand and dust carried by the wind.
Deflation - removal of fine-grained soil of sand by the wind which can bare rocks or leave a coarse grain lag deposit.
3 types of wind transport
Reputation, or surface creep
Saltation
Suspention
Principle of Uniformitarianism
Processes we see on Earth today worked the same way in the Geological Past
4 Controls on weathering and their factors
Properties of the rock -> Structure and Solubility
Climate -> Temperature and Rainfall
Soil -> Thickness and Organic Content
Time -> Length exposed
4 Types of Chemical weathering
Water
CO2 and acids
Soils
Oxygen
Granite Composition
Biotite
Quartz
2 Feldspars
Describe the Chemical Weathering of Feldspar
Hydrolysis/Reacts in water to form Kaolinite clay
3 steps of CO2 dissolving silicates
Dissolves Cations and Silica
Hydrates the minerals
Neutralizes the solution
The chemical formula for Feldspar Weathering
Feldspar + Carbonic acid + Water -> Kaolinite + Silica + Potassium+ + Bicarbonate-
2 KAlSi3O8 + 2 H2CO3 + H2O -> Al2Si2O5(OH)4 + 4 SiO2 + 2 K + 2 HCO3
3 Soil Chemical Weathering causes
Constant Humidity
Acids - Organic and Bacterial respiration
Plant and Animal activity
Describe the common oxygen weathering process
When iron is released from weathered silicate minerals
It oxidizes from Ferrous (2+) to Ferric (3+) and forms minerals such as hematite
Mineral Solubility
The maximum amount of mineral dissolved in a quantity of water
Mineral rate of dissolution
Speed with which a mineral dissolves in water
6 Types of Physical Weathering
1) Abrasive Processes
Fracturing Processes:
2) Activities of Organisms - Burrowing animals can break rocks and stir sediments causing physical weathering. Animals that burrow can also bring fresh material to the surface where physical and chemical weathering can work more efficiently. Plant roots in search of nutrients in water grow into fractures.
3) Frost Wedging e.g. Freeze-thaw - as water freezes its volume increases by roughly 9%. Liquid water percolates into existing cracks within a rock. The pressure of expanding ice causes cracks to widen and extend.
4)Thermal Expansion and Contraction - When minerals are subjected to different temperature ranges they expand and contract. Rapid temperature fluctuations such as day-night cycles can cause individual grains in rocks to expand and contract at different rates. Individual grains can be squeezed from the rock surface or fractures can form to relieve stress.
5) Exfoliation/Sheeting - a process in which large flat or curved sheets of rock fracture and are detached from the outcrop due to pressure release
6) Cristalisation and expansion - water that has dissolved salt in it penetrates cracks in rocks. As the water evaporates, salt crystals begin to form.
Exfoliation/Sheeting
- a process in which large flat or curved sheets of rock fracture and are detached from the outcrop due to pressure release
Frost Wedging
e.g. Freeze-thaw - as water freezes its volume increases by roughly 9%. Liquid water percolates into existing cracks within a rock. The pressure of expanding ice causes cracks to widen and extend.
