Presentation on the different factors controlling weathering. In this we discuss the basic concepts is weathering and explain in breif the various factors controlling them.

1. FACTORS
CONTROLLING
WEATHERING
SHARIK SHAMSUDHIEN
ROLL NO: 183104008

2. Content
• Weathering
• Factors Controlling Weathering
• Endogenetic And Exogenetic factors
• Different factors Controlling Weathering
• References

3. Weathering
• The process of disintegration and decomposition of rocks insitu is
generally called weathering.
• It means weathering is a static process.
• According to C.D. Oilier (1969) ‘weathering is the breakdown and
alteration of minerals near the earth’s surface to products that are
more in equilibrium with newly imposed physico-chemical
conditions.’
• Weathering is essentially the breakdown of rocks due to chemical
and mechanical processes at their places.
• Weathering is the breaking down of rocks and other materials on
the earth’s surface

4. Factors Controlling Weathering
• The nature and magnitude of weathering differs from place to
place and region to region.
• Weathering of rocks is affected and controlled by the agents
of weathering, lithological and structural characteristics of
rocks, height and slope factors.
• Besides, climatic conditions, topography and reliefs, flora and
microfauna also affect different processes of weathering to
greater extent.
• For example, disintegration of rocks is more effective in hot
and dry region and in the regions where frost action is more
dominant while chemical decomposition is more prevalent in
hot and humid and temperate humid regions.

5. • The Geological Weathering factors which are related to the
rock characteristics are called as Endogenetic, Such as
– Mineral composition
– Rock Structure
– Particle size
• The factors other than rock characteristics; pertaining to the
external environment are called Exogenetic , Such as
– Climate
– Water
– Gravity
– Pollution
– And other Weathering factors

7. CLIMATE
• This is the most important factor affecting weathering of rocks.
• The extent of weathering is dependent on the average
atmospheric condition prevailing in a region over a long period of
time.
There are two factors that play in weathering, they are :-
Temperature and Precipitation.
• Warm climates affect by chemical weathering while cold climates
affect by physical weathering (particularly by frost action). In
either case the weathering is more pronounced with more
moisture content.
• At higher temperatures chemical reactions are likely to take place
faster.
• Because of abundance of moisture and high temperature
leaching process and solution of rocks are more effective in the
humid tropics.

8. • Biological activities are supported by hot moist climates.
• In fact a hot moist climate provides the most ideal environment
for fast chemical weathering.
• The rocks in dry temperate climates are more susceptible to
mechanical weathering than chemical weathering because
alternate expansion and contraction of cracks, fractures and
joints of rocks due to alternate freeze and thaw of water
accumulated in these cracks and fractures weaken the rocks.
• Physical weathering by frost action is most likely in cold climate
where freeze and thaw occur alternately during the cold
weather. In this case again precipitation is the main factor. In
the absence of water ice cannot form and frost action is not
possible.
• Hence an effective frost action occurs in the cold moist climate.

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11. PARTICLE SIZE
• Most weathering occurs on exposed surfaces of rocks and
minerals.
• Rate of chemical weathering is affected by size of rock particles.
If the rock pieces are smaller, the weathering is faster.
• This is because if the rock pieces are smaller, the surface area
exposed to weather action is greater.
• The more surface area a rock has, the more quickly it will
weather. When a block is cut into smaller pieces, it has more
surface area. Therefore weathering is faster than a large block
of rock .

13. MINERAL COMPOSITION AND STRUCTURE OF ROCKS
• Since weathering involves disintegration and decomposition of
rocks and hence mineral composition, joint patterns, layering
system, faulting, folding etc. largely affect the nature and intensity
of weathering. For example, carbonate rocks (e.g. calcium
carbonate, magnesium carbonate etc.) having more soluble
minerals are easily affected by chemical weathering.
• Well jointed rocks are more subjected to mechanical
disintegration.
• Rocks having vertical strata are easily loosened and broken down
due to temperature changes, frost action, water and wind actions.
• On the other hand, the rocks having horizontal beds are more
compact and are less affected by the mechanisms of
disintegration and decomposition.

14. • We know, the chemical properties of a rock depend on the
mineral composition to a great extent.
• Mineral in a rock may readily react with acids, water or
oxygen causing considerable weathering.
• For example limestone can get severely acted upon by even
very mildly acidic rainwater. Limestone caves, underground
caves, cavern, or Karst topography are a result of this kind of
weathering. Karst topography usually forms sinkholes.
• Granite on the contrary mostly containing silica remains
unaffected by such agents
• Some minerals resist weathering. Quartz is a mineral that
weathers slowly. Rocks made up of minerals
such as feldspar, calcite, and iron, weather more quickly

15. Honeycomb Weathering Sandstone
Oregon coast, U.S

16. EXPOSURE
• The extent of exposure i.e. the extent to which the rock comes into
contact with the agents of weather is an important factor affecting
the weathering.
• In some situations, vegetation, soil, ice, etc. may cover a rock,
thereby reducing the area exposed to weather action.
• Such rocks so protected weather slowly compared to rocks whose
surfaces are wholly exposed to weather.
• Slope of the region is also a factor affecting weathering.
• Where the slopes are steep, loose materials are displaced downhill
either by gravity or by erosion resulting in continuous exposure of
the fresh rock.

18. NATURE OF SLOPE/GRAVITY
• Ground slope controls mechanical disintegration of
rocks and mass movement of weathered products
down the slope.
• The rocks in the regions of steep hillslope are easily
disintegrated due to mechanical weathering and the
weathering materials are instantaneously moved down
the hillslope in the form of rock-fall, debris fall and
slide, talus creep etc.
• Instantaneous removal of weathering products allows
continuous exposure of rocks to atmospheric
conditions for further weathering.
• The regions of gentle and moderate ground slope are
less affected by mechanical disintegration

19. • Force of gravity can pull rocks and sediment towards the
Earth.
• The rocks falling and colliding with other rocks.
Oddiecombie, UK

20. FLORAL EFFECTS
• The nature of weathering is largely determined by the
presence or absence of vegetation’s in a particular region.
• It may be pointed out that vegetation is partly a factor of
weathering and partly a protector of rocks.
• In fact, vegetation’s bind the rocks through their network of
roots and thus protect them from weathering and erosion but
the same time the penetration of roots weakens the rocks by
breaking them into several blocks.
• Dense vegetation’s protect the ground surface from the direct
impact of sun rays.
• The microorganisms associated with the roots of plants and
trees encourage decomposition and disintegration of rocks
through physiobiochemical weathering.

22. TIME AND POLLUTION
• The process of weathering is a time taking process.
• The duration of time for which a rock is exposed to weather
determines the extent of weathering.
• Very strong rocks, however strong they might be will severely
undergo weathering in hundreds of years.
• Pollution speeds up weathering. Factories and cars release carbon
dioxide and other gases into the air.
• These gases dissolve in the rainwater, causing acid rain to form.
• Acid rain contains nitric and sulfuric acid, causing rocks and
minerals to dissolve faster.

24. References
• The Earths Dynamic surface by K. Siddhartha
• Weathering of Rocks: Meaning, Controlling Factors and Types-
Sirisha P._Geography Notes.com
• http://www.geographynotes.com/rocks/weathering-of-rocks-
meaning-controlling-factors-and-types-rocks-geography/2350
• http://www.yourarticlelibrary.com/geology/weathering-of-rocks-5-
factors-geology/91154
• http://the-gneiss-blog.tumblr.com/post/125917254829/factors-

25. Thank you