A basic introduction to processes in Physical Geology

1. PHYSICAL GEOLOGY
PART 1A
THE EARTHLY PROCESSES : WEATHERING
-BISHAL SAHA

2. Physical geology is thestudy of various ongoinggeologic events
and processes on thesurface of theearth.

3. The various primitive processes
• Weathering : The process of disintegration of rocks due to
some physical, chemical and biological conditions is called
weathering. The weathered debris is called sediments.
• Erosion : The process of washing away of the weathered
material is called erosion.
• Transport : The journey of the washed out debris until it
gets deposited is called transport.
• Deposition : The settling down of the washed out
sediments at a favourable location is called deposition.

4. TYPES OF WEATHERING:
Weathering
Physical Chemical Biological Artificial
1. Exfoliation 1. Carbonation 1. Roddents 1. Quarrying
2. Frost action 2. Oxidation 2. Trees 2. Drilling
3. Salt wedging 3. Reduction 3. Mining
4. Temperature 4. Hydrolysis
triggered 5. Acidification

5. Exfoliation
Courtesy : science struck
Frost wedging
Source : Bishal Saha
Salt wedging
Courtesy : science struck
Temperature triggered weathering
Courtesy : wikiversity
Physical weathering brings about changes in
dimension and not composition of rock.

6. Oxidation
Source : Anupam
Paramanik
Carbonation in
limestone
Source :
internet
Soil acidification
Source : internet
Hydrolysis . Source : internet
2Fe2O3 -> 4FeO+O2
Reduction
Chemical weathering brings about compositional
changes in rocks.

7. • Mobile ions : They are
the first ones to get
removed by
weathering. Eg : Ca,
Mg, Na, K.
• Immobile ions : They
do not get easily
affected by weathering
and erosion. Eg :
Fe(+3), Al, Si.
CIA=
𝑨𝒍𝟐𝑶𝟑
𝑨𝒍𝟐𝑶𝟑+𝑪𝒂𝑶+𝑵𝒂𝟐𝑶+𝑲𝟐𝑶
* 100
CHEMICAL INDEXOF ALTERATION(CIA)

8. GOLDICHWEATHERING SERIES
• 1938 : Samuel
Goldich published
his works on the
effect of chemical
weathering on
igneous silicates.
• The relative effect of
chemical weathering
are given in form of
a series called
Goldich’s weathering
series.
Source : Blogspot

9. Tree roots trigger weathering
Source : internet
Roddent burrowing in rocks
Source : internet
Biological weathering is triggered by growing
roots of trees or burrowing action of rodents.

10. Drilling in rocks
Source : internet
Ledason quarry,
Purulia
Zawar Mines, Rajasthan
Artificial forms of weathering are human induced.
They are the fastest forms of weathering.

11. to be continued