c1 - processes associated with weathering and mass wasting
What are Gradational Processes?
Gradation is "the levelling of a land surface, resulting from the concerted action of erosion and deposition."
http://dictionary.reference.com/browse/gradational
Weathering is the breaking down of the structure of rock or soil leaving it more vulnerable to erosion.
http://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3461.html
Weathering processes can be divided into two categories:
http://www.physicalgeography.net/fundamentals/10r.html
1. Chemical - the structure of rock or soil is weakened by chemical reactions with substances such as acids, air and water
http://www.agriinfo.in/?page=topic&superid=4&topicid=249
- Solution / Carbonation = calcareous rocks (containing calcium eg. limestone and chalk) are dissolved by weak acids in water - carbon dioxide from the air dissolves in water to produce carbonic acid
- Oxidation = soil and rocks containing iron and magnesium (eg. sandstone) 'rust' when they react with oxygen.
- Hydrolysis = weak acids in water react with minerals like feldspar weakening their structure to produce clays
- Hydration = minerals in rocks react with hydrogen ions in water and increase in volume of crystals (eg. granite forms kaolinite)
- Biological = organic acids produced by decaying plant matter, lichens and mosses break down the chemical structure of soils and rocks eg. chelation
2. Mechanical / Physical - the structure of soil or rock is weakened by expansion and / or contraction due to changes in temperature, pressure, water and vegetation
http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/revision/6/
- Insolation / Exfoliation = repeated heating and cooling of rock cause it to expand (when heated) and contract (when cooled), this gradually weakens bonds between layers within rock. Common in deserts and areas within a large diurnal temperature range.
- Wetting and Drying / Slacking = repeated 'wetting and drying' of rocks allow water molecules to accumulate between crystals and grains weakening the rock structure. Common in coastal and river environments.
- Freeze-thaw / Frost Shattering / Ice Wedging = water in rocks freezes and expands, weakening the rock structure, this is repeated when temperatures are low eg. during winter months, or at high altitudes.
- Pressure-Release = when a rock is under pressure (eg. covered by ice) the structure is compacted, when the pressure is released (eg ice melts) the rock begins to rebound / expand weakening the rock structure.
- Crystalization = water containing salts enter the rock, when the water evaporates, the salts begin to form crystals, as the crystals grow, they expand and weaken the rock structure eg. in coastal environments.
- Biological = plant roots growing between rock layers weaken the rock structure / burrowing animals expose the rock to other forms of weathering and erosion eg. uncovering rock surface / enabling water to seep into rock structure.
Gradation is "the levelling of a land surface, resulting from the concerted action of erosion and deposition."
http://dictionary.reference.com/browse/gradational
Weathering is the breaking down of the structure of rock or soil leaving it more vulnerable to erosion.
http://www.geolsoc.org.uk/ks3/gsl/education/resources/rockcycle/page3461.html
Weathering processes can be divided into two categories:
http://www.physicalgeography.net/fundamentals/10r.html
1. Chemical - the structure of rock or soil is weakened by chemical reactions with substances such as acids, air and water
http://www.agriinfo.in/?page=topic&superid=4&topicid=249
- Solution / Carbonation = calcareous rocks (containing calcium eg. limestone and chalk) are dissolved by weak acids in water - carbon dioxide from the air dissolves in water to produce carbonic acid
- Oxidation = soil and rocks containing iron and magnesium (eg. sandstone) 'rust' when they react with oxygen.
- Hydrolysis = weak acids in water react with minerals like feldspar weakening their structure to produce clays
- Hydration = minerals in rocks react with hydrogen ions in water and increase in volume of crystals (eg. granite forms kaolinite)
- Biological = organic acids produced by decaying plant matter, lichens and mosses break down the chemical structure of soils and rocks eg. chelation
2. Mechanical / Physical - the structure of soil or rock is weakened by expansion and / or contraction due to changes in temperature, pressure, water and vegetation
http://www.bbc.co.uk/bitesize/ks3/science/environment_earth_universe/rock_cycle/revision/6/
- Insolation / Exfoliation = repeated heating and cooling of rock cause it to expand (when heated) and contract (when cooled), this gradually weakens bonds between layers within rock. Common in deserts and areas within a large diurnal temperature range.
- Wetting and Drying / Slacking = repeated 'wetting and drying' of rocks allow water molecules to accumulate between crystals and grains weakening the rock structure. Common in coastal and river environments.
- Freeze-thaw / Frost Shattering / Ice Wedging = water in rocks freezes and expands, weakening the rock structure, this is repeated when temperatures are low eg. during winter months, or at high altitudes.
- Pressure-Release = when a rock is under pressure (eg. covered by ice) the structure is compacted, when the pressure is released (eg ice melts) the rock begins to rebound / expand weakening the rock structure.
- Crystalization = water containing salts enter the rock, when the water evaporates, the salts begin to form crystals, as the crystals grow, they expand and weaken the rock structure eg. in coastal environments.
- Biological = plant roots growing between rock layers weaken the rock structure / burrowing animals expose the rock to other forms of weathering and erosion eg. uncovering rock surface / enabling water to seep into rock structure.
Erosion is the wearing away and removal of soil and rock by the action of water, wind and ice.
http://www.britannica.com/EBchecked/topic/191809/erosion
The main processes of erosion include:
- Abrasion = debris particles (eg. sand or rock fragments) cause scouring of the rock or soil as they are carried across the surface by wind, water or ice.
- Attrition = the force of moving wind, water or ice breaks down debris particles into smaller pieces when they collide with the rock surface, or other particles.
- Hydraulic Action = the force of moving water increases water or air pressure in cracks in the soil or rock surface, eventually widening them and breaking them apart.
- Corrosion (Solution) = weak acids in water (usually carbonic acid from dissolved carbon dioxide) gradually dissolve calcareous rocks such as chalk and limestone.
What is Mass Wasting?
Mass Wasting involves the slipping, slumping, falling and flowing of soil or rock down a slope.
This website is great and very detailed, use it to help you fill in the notes sheets below.
http://geology.campus.ad.csulb.edu/people/bperry/Mass%20Wasting/Types_of_Mass_Wasting.htm
http://www.britannica.com/EBchecked/topic/191809/erosion
The main processes of erosion include:
- Abrasion = debris particles (eg. sand or rock fragments) cause scouring of the rock or soil as they are carried across the surface by wind, water or ice.
- Attrition = the force of moving wind, water or ice breaks down debris particles into smaller pieces when they collide with the rock surface, or other particles.
- Hydraulic Action = the force of moving water increases water or air pressure in cracks in the soil or rock surface, eventually widening them and breaking them apart.
- Corrosion (Solution) = weak acids in water (usually carbonic acid from dissolved carbon dioxide) gradually dissolve calcareous rocks such as chalk and limestone.
What is Mass Wasting?
Mass Wasting involves the slipping, slumping, falling and flowing of soil or rock down a slope.
This website is great and very detailed, use it to help you fill in the notes sheets below.
http://geology.campus.ad.csulb.edu/people/bperry/Mass%20Wasting/Types_of_Mass_Wasting.htm
There are various factors which increase the likelihood and rate of different types of Mass Wasting:
- Steepness of slope gradient, the steeper the slope, the greater the influence of gravity on particles
- Rock structure, bedding planes and faults can increase vulnerability to movements (see slide above)
- Rock type, sedimentary and unconsolidated sediments are more vulnerable to movement than igneous rocks
- Level of water saturation, the greater the saturation, the lower the friction between particles
- Vegetation cover, plant roots help to hold surface together
- Human activity, mining can cause vibrations which trigger movement / poor slope management can lead to undercutting slopes
- Steepness of slope gradient, the steeper the slope, the greater the influence of gravity on particles
- Rock structure, bedding planes and faults can increase vulnerability to movements (see slide above)
- Rock type, sedimentary and unconsolidated sediments are more vulnerable to movement than igneous rocks
- Level of water saturation, the greater the saturation, the lower the friction between particles
- Vegetation cover, plant roots help to hold surface together
- Human activity, mining can cause vibrations which trigger movement / poor slope management can lead to undercutting slopes