Bio-geography

M-Sand (Manufacured) is sand produced by crushing rocks, quarry stones or larger aggregates pieces into sand-sized particles. It is used for construction purposes in cement or concrete.
M-sand differs from natural river sand in its physical and mineralogical properties.
To bar the unregulated sale of sub-standard M-sand, Tamil Nadu government is to implement a policy with a legal framework for itsproduction and sale.

Statement 1 is incorrect. Yellow dust refers to sand from Mongolian and Chinese deserts that blow into North and South Korea at certain times of the year. It is intermingled with toxic dust that for years has raised health concerns in both countries.
Statement 2 is incorrect. WHO has not issued any such advisory.
North Korea has though warned its citizens to stay indoors over fears that “yellow dust” which blows in from China could bring coronavirus with it.
# The US Centres for Disease Control has said coronavirus can remain suspended in the air “for hours”. However, it also says it is extremely rare for someone to be infected this way – especially outdoors. The main way people get infected is from standing in close proximity to someone who is infected who then coughs, sneezes or talks, spreading the virus through droplets.

Red soils.
Statement 1 is correct: Red soil develops on crystalline igneous rocks in areas of low
rainfall in the eastern and southern part of the Deccan Plateau. Along the piedmont zone of
the Western Ghat, long stretch of area is occupied by red loamy soil. Yellow and red soils
are also found in parts of Odisha and Chattisgarh and in the southern parts of the middle
Ganga plain.
Statement 2 is correct: The soil develops a reddish colour due to a wide diffusion of iron
in crystalline and metamorphic rocks. It looks yellow when it occurs in a hydrated form.
Statement 3 is incorrect: The fine-grained red and yellow soils are normally fertile,
whereas coarse-grained soils found in dry upland areas are poor in fertility. They are
generally poor in nitrogen, phosphorous, Potassium and humus.

Aridisols are largest single soil order occurs in dry regions of the world.
•These soils occupy nearly 19 per cent of the earth’s land surface.
•Pale and light near the surface, deficit in moisture.
•These soils are lack in organic matter.
•Salinisation is the main problem of these soils.
•Salinisation complicates farming in Aridisols.

Geographically, black soils are spread over 5.46 lakh sq km (i.e. 16.6 per
cent of the total geographical area of the country) encompassed between 15°N to 25°N
latitudes and 72°E to 82°E longitudes.
•This is the region of high temperature and low rainfall. It is, therefore, a soil group of
the dry and hot regions of the Peninsula.
•These soils are mainly found in Maharashtra, Madhya Pradesh, parts of Karnataka,
Andhra Pradesh, Gujarat and Tamil Nadu.
•The black colour of this soil may even be derived from crystalline schists and basic
gneisses such as in Tamil Nadu and parts of Andhra Pradesh.
•The black soil is very retentive of moisture. It swells greatly and becomes sticky
when wet in rainy season. Under such conditions, it is almost impossible to work on
such soil because the plough gets stuck in the mud.
•However, in the hot dry season, the moisture evaporates, the soil shrinks and is
seamed with broad and deep cracks, often 10 to 15 cm wide and upto a meter deep.
This permits oxygenation of the soil to sufficient depths and the soil has
extraordinary fertility.
•Remarkably “self ploughed” by loosened particles fallen from the ground into the
cracks, the soil “swallows” itself and retains soil moisture. This soil has been used
for growing a variety of crops for centuries without adding fertilizers and manures,
or even fallowing with little or no evidence of exhaustion.
•Because of their high fertility and retentivity of moisture, the black soils are widely
used for producing several important crops.
•Some of the major crops grown on the black soils are cotton, wheat, jowar, linseed,
Virginia tobacco, castor, sunflower and millets.
•Rice and sugarcane are equally important where irrigation facilities are available.
Large varieties of vegetables and fruits are also successfully grown on the black
soils.

The Soils can be classified on the basis of dominating factors:
Zonal Soil – These soils occur in broad geographical areas or zones.
• They are influenced more by the climate and vegetation of the area rather than the rock-type.
• They are mature, as a result of stable conditions over a long period of time.
• For example – red soils, black soils, laterite soils, desert soils etc.

Azonal Soil – It is that soil which has been developed by the process of deposition by the agents of erosion.
• It means that it has been made by the fine rocky particles transported from the far-off regions.
• These are immature soils and lack well-developed soil profiles.
• This may be due to the non-availability of sufficient time for them to develop fully or due to the location on very steep slopes which prohibits profile development.
• For Example – alluvial and loess soils.

Intrazonal Soil – These soils occur within other zonal soils.
• It is a well-developed soil reflecting the influence of some local factor of relief, parent material, or age rather than of climate and vegetation.
• For example, calcareous soil (soils which develop from limestone), peat soil.

Latosols are soils found under tropical rainforests which have a relatively high content of iron and aluminum oxides. They are typically classified as oxisols or ferralsols

Assam is traditionally flood prone, and the 1,055 sq km KNPTR — sandwiched between the Brahmaputra River and the Karbi Anglong Hills — is no exception.

 Among experts there is a consensus that floods are necessary for Kaziranga by virtue of its ecosystem.

 “It is a riverine ecosystem, not a solid landmass-based ecosystem,” said by Director, KNPTR, “The system won’t survive without water.”

 The entire area of Kaziranga — formed by alluvial deposits from the Brahmaputra and its tributaries — is centred around the river.

Lateritic is a soil and rock type rich in iron and aluminum and is commonly considered to have formed in hot and wet tropical areas.

 Nearly all lateritics are of rusty-red coloration, because of high iron oxide content.

 They develop by intensive and prolonged weathering of the underlying parent rock.

 The lateritic soils are commonly found in Karnataka, Kerala, Tamil Nadu, Madhya Pradesh and the hilly areas of Orissa and Assam.