2. Weathering
Types of weathering
Mechanical and Chemical weathering
Biological weathering
Pillars of weathering
Mass wasting
Classification of Mass Wasting
3. Weathering processes occur at or near the Earth’s surface
and produce changes to the landscape that influence
surface and subsurface topography and landform
development.
is the physical disintegration or chemical alteration of
rocks at or near the Earth’s surface
Erosion is the physical removal and transportation of
weathered material by water, wind, ice, or gravity
4. 1 :Mechanical (physical) weathering is the physical
disintegration and reduction in the size of the rocks without
changing their chemical composition.
Examples: exfoliation, frost wedging, salt wedging,
temperature changes, and abrasion
2 :Chemical weathering decomposes, dissolves, alters, or
weakens the rock through chemical processes to form
residual materials
Examples: carbonation, hydration, hydrolosis, oxidation,
and solution
5. 3 :Biological weathering is the disintegration
or decay of rocks and minerals caused by
chemical or physical agents of organisms.
Examples: organic activity from lichen and
algae, rock disintegration by plant or root
growth, burrowing and tunneling organisms,
and acid secretion
6. Mechanical weathering is the physical
disintegration and reduction in the size of the
rocks without changing their chemical
composition.
Exfoliation
Frost Wedging
Salt Wedging
Temperature Changes
Abrasion
7. Exfoliation is a mechanical weathering process
whereby pressure in a rock is released along
parallel alignments near the surface of the
bedrock and layers or slabs of the rock along
these alignments break off from the bedrock and
move downhill by gravity.
8. Frost wedging is a mechanical weathering process
caused by the freeze-thaw action of water that is
trapped between cracks in the rock.
When water freezes, it expands and applies
pressure to the surrounding rock forcing the rock
to accommodate the expansion of the ice.
This process gradually weakens, cracks, and
breaks the rock through repetitive freeze-thaw
weathering cycles
9. Daily (diurnal) and seasonal temperature changes affect
certain minerals and facilitates the mechanical weathering
of bedrock.
Warmer temperatures may cause some minerals to
expand, and cooler temperatures cause them to contract.
This gradual expansion and contraction of mineral grains
weakens the rock causing it to break apart into smaller
fragments or to fracture.
This process is more common in desert climates because
they experience extreme fluctuations in daily temperature
changes.
Temperature changes are often not the dominant form of
weathering, but instead temperature changes tend to
accelerate other forms of weathering already occurring.
10. Chemical weathering decomposes, dissolves, alters, or
weakens the rock through chemical processes to form
residual materials.
Carbonation
Hydrolysis
Hydration
Oxidation
Solution
11. Mostly in humid areas
CO2 dissolves in rain water and creates carbonic acid
Carbonic acid easily weathers limestone and marble
CaCo3+H2CO3 Ca2+ +
2HCO3
12. Oxidation occurs when oxygen and water react with
iron-rich minerals and weaken the structure of the
mineral.
During oxidation the minerals in the rock will change
colors, taking on a ‘rusty’, reddishorange appearance
13. Solution occurs when minerals in rock
dissolve directly into water.
Solution most commonly occurs on rocks
containing carbonates such as limestone, but
may also affect rocks with large amount of
halite, or rock salt.
14. Hydrolysis is a chemical reaction between H+ and
OHions in water and the minerals in the rock.
The H+ ions in the water react with the minerals
to produce weak acids.
The reaction creates new compounds which tend
to be softer and weaker than the original parent
rock material.
15. Compounds from burning coal, oil and gas react
chemically with water forming acids.
Acid rain causes very rapid chemical weathering
16. Biological weathering is the disintegration or
decay of rocks and minerals caused by
chemical or physical agents of organisms.
• Animal And Insects
• Vegetation
• Human Activities
17. Nature of Rock
Slope of Land
Joints
Vegetal Cover
Climate
20. “It is downslope movement of masses of bedrock,
rock debris, regolith or soil, under the direct
influence of gravity”
The downslope transfer of material through the
direct action of gravity .
Component of erosion and transport of sediment
Follows weathering, which weakens and breaks the
rock.
21. Type of Material
Bedrock - Rock
Unconsolidated material - Debris Soil
Regolith Sediment
Rate of movement
Fast moving, which are calculated in km/hr
E.g. Rock avalanches moving up to speed of
200 km/hr Slow moving, which are calculated
in mm/yr or cm/yr
E.g. creep
22. Fall
It is the free fall of material of any size It fall
directly to the base of the slope or move in a
series of leaps and bounds over other rocks
along the way.
23. Slide occurring on a planar surface or on a
slip plane
Slide occurring along a curved slip plane
26. Downward slipping (slide) of a mass of rock
or unconsolidated material moving as a unit
Rock or unconsolidated material move in a
curved path
Does not move very fast or far away
May be single or multiple blocks
Caused by overloading, excess of water, over
steeping, removal of anchoring material
27.
28. Sliding of blocks of bed rock along a defined
slippage plane
Sudden, rapid and destructive movement
Takes place where rock strata are
inclined(steep slopes), joints or fracture exist
parallel to slope, underlying layer is thin layer
of clay or river cut the anchoring material
Can be triggered by rain falls or ground
vibration
29.
30. Gradual downslope movement of soil or
regolith– mm/yr
Expansion/contraction, freezing/thawing or
wetting/drying cycles play a key role
Process so slow one cannot observe it in
action
Enhanced by burrowing organisms, periods of
prolonged rains or snow
31.
32. Special type of creep
Occurs in regions underlain by permafrost
(permanently frozen, water-bearing ground)
During warm periods top portion (active
layer) thaws and becomes saturated
Melt waters are unable to percolate into
permafrost layer below
Saturated (active) layer flows over frozen
layers
It can occur on slopes as gentle as 2-3
degree 52 SOLIFLUC
33.
34. A type of debris flow, generally move slower
Forms on hillside humid areas as a result of
excessive rainfall
Water saturates the clay-rich regolith and
material break away and flow a short distance
downslope
Speed of earthflow vary from few meters per
hour to several meters per minutes
Can remain active over periods of years
35.
36. Mass wasting is the movement of earth
material under influence of gravity
It is responsible for shaping the earth and
forming different land forms
It causes destruction to humans beings if it
occurs in living areas
