Weathering Types Flashcards
1
Q
Physical/Mechanical Weathering
A
- Disintegration of rock by physical processes without changes in chemical or mineral composition
- Regions devoid of vegetation
- Stress applied in and around rocks
2
Q
Pressure/Release
A
- Disruptive expansion when the overburden is removed from rocks that have been under high pressure at depth
- Rocks created under high pressure exposed to atmosphere, substantial release in pressure
3
Q
Freeze-thaw
A
- Most common form of mechanical weathering
- Water enters cracks in daytime, freezes overnight at -22
- ice occupies 9% more volume than water, causing rocks to shatter off of the main body
4
Q
Salt Crystalization
A
- if water entering pore space in rocks is slightly saline, as the water evaporates, salt crystals are likely to form
- growing larger + stresses in rock
- disintegrate and break apart
- often occurs in deserts where capillary action draws moisture to the surface
5
Q
Thermal Expansion and Contraction
A
- Rocks expand when heated and contract when cooled
- Most common in deserts
- Situations of extreme temperature
- Changes in temperature can cause different minerals within a rock to expand and contract at different rates
6
Q
Biological Weathering
A
- Plant roots grow into and extend along joins and crevices and pry rocks apart over time
- Some plants that grow on the rock surface can release a weak acid and work to further weather the rock
7
Q
Chemical Weathering
A
- Break down of rock resulting from surface processes that change the chemical composition of the original material
- Chemical reactions between the elements and the atmosphere and or groundwater, produces a change in substances and solubles
8
Q
Role of Water
A
Rate and intensity of chemical weather is greatly influenced by the amount of precipitation in the area
- water removes the weathering products to expose fresh rock for continued weathering
9
Q
Solution
A
- Some minerals are soluble and dissolve in water
- Minerals composing the earths crust are soluble to vary degrees in water
- Water also removes the weathering products to expose fresh rock for continued weather
10
Q
Factors that Increase Rates of Solubility
A
- pH of water greatly affects the rate of solution - a lower pH = more acidic = faster break down of rocks
- Solubility of materials often increases with rising temperatures
- Circulation also hastens solution by removing dissolves ions from the mineral surface and replace them with fresh water
11
Q
Oxidation
A
- Occurs when rocks are exposed to oxygen via the air or water
- Causes rocks to crumble more easily
- Ferric oxides (rust) are insoluble, instead they precipitate as solid compounds on the surface of the rock giving it a yellow/brown/red coating
12
Q
Hydrolysis
A
- Most significant chemical process in the decomposition of rocks and the formation of clays
- Hydrogen in water reacts with minerals in the rock
- The formation of the new mineral disrupts the mineral structure and causes the rock to begin breaking down on the mineral level
13
Q
Carbonation
A
- Rain water contains carbon dioxide in the solution - Carbonic Acid
- Weak acid reacts with rock with are composed of calcium carbonate
- Limestone dissolves and removed by running water
- Carboniferous limestone which is well-joined and layered in combination with carbonation results in the development of a variety of Karst landforms including cavern system
14
Q
Types of mass wasting
A
Rockfall
Rockslide
Slump
Soliflucation
15
Q
Slump
A
Most likely in consolidated clays or soils (think slipping back in your seat)
