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SAI INTERNATIONAL SCHOOL, BHUBANESWAR.

Class VIII: SOCIAL STUDIES – GEOGRAPHY

CHAPTER - 2- LAND, SOIL, WATER, NATURAL VEGETATION AND
WILDLIFE RESOURCES

(VIRTUAL CLASSES)

NOTES FOR CHAPTER-2- Land, Soil, Water, Natural Vegetation and Wildlife Resources

SUBTOPIC- SoiL and Factors of Soil Formation:
A- SOIL:-
 is the thin layer of coarse and rough substance covering the earth’s surface
 is made up of organic matter, minerals and weathered rocks
 is different in different geographic regions

B- SOIL PROFILE:- refers to the layered structure which spreads from the parent rocks to the top
soil surface.
 The four layers of soil profile are:
st
 1 layer is the top soil with humus and vegetation
nd
 2 layer is the sub soil with sand, silt and clay
rd
 3 layer comprises of weathered rock material
th
 4 layer is the parent rock (bed rock).
 The thickness of the soil profile is affected by the time taken for the soil to form.
 Older soil has a thicker soil profile compared to new soil.
 The types of soil found in India include Alluvial, Black, Red, Laterite, Desert and
Montane.

C.Factorsaffecting Soil Formation:Various factors affect the physical and chemical properties of
soil.The major factors are the nature of the parent rock and the climate of that area.

a. Parent rock- determines the texture, color, chemical properties, minerals content and permeability
of the soil
b. Climatic conditions- like temperature and rainfalldetermine the rate of weathering and the
formation of humus.
c. Relief determines the altitude and slope and accumulation of soil. As steep slopes are more prone
to soil erosion the layer of soil on them is generally thin whereas flat areas have a thick layer of soil
as they retain the layers of soil for longer periods.
d. Flora and fauna- affect the rate of humus (degraded organic material) formation in soil.
Humus increases the soil fertility.
e. Micro-organismplay a very important role in soil nutrient cycle and minerals balance. They help in
the process of decomposition of organic dead matter.
f. Timedetermines the thickness of soil profile. it takes hundreds of years to make just one centimetre
of soil.

D.Weathering of rocks.-Rocksbreakdown and decay due to changes in temperature, frost and
actions of living organism. It is a very slow process and is called weathering.During weathering, rock
debris gets mixed with organic matter and minerals thus increasing the fertility of the soil.