Weathering Flashcards
Name 4 types of erosion
Rainsplash
Sheetflow
Surface wash (gullying)
Throughflow
Name 5 types of mass movement
Fall Slide Slump Flow e.g. Solifluction Creep
Mass movement
The downslope movement of material under the influence if gravity
Erosion
Wearing away of rock by a moving agent (river, sea, ice, wind)
Weathering
Disintegration and decomposition of rocks in situ
Freeze-thaw
Water in joints and cracks freezes and expands by 10% and exerts pressure up to 2100kg/cm^2.
Salt crystal growth
Sodium sulphate and sodium carbonate expand by 300% when temperatures fluctuate around 26-28degreesC. When water evaporates, salt crystals grow in rock pores.
Exfoliation
Rocks heat up in daytime temps and contract in colder night time temps. As rock is a poor conductor if heat, stresses take place only in the outer layers causing peeling to occur.
Pressure release
Overlying rocks removed by erosion cause underlying ones to expand and fracture parallel to the surface. Also occurs when great weight such as glacier is removed.
Carbonation/solution
Rainfall and dissolved CO2 form a weak carbonic acid (organic acids acidify water too). CaCO3 reacts with the acid water and forms calcium bicarbonate or hydrogen bicarbonate, which is soluble and removed by percolation of water
Hydrolysis
Orthoclase feldspar reacts with acid water and forms kaolinite (or kaolin or china clay), silicic acid and potassium hydroxyl. Acid and hydroxyl are removed in the solution leaving china clay behind as the end product. Other minerals such as quartz and mica remain in the kaolin
Hydration
Certain minerals absorb water, expand and change e.g. Anhydrite changed to gypsum during hydration
Oxidation
Iron compounds react with oxygen to produce a reddish brown coating
Biological weathering
Roots growing and animals burrowing in cracks force them wider. Chemical changes formed by release of organic acids from plants.
