Daily Quiz: UPSC Prelims Marathon (Geography) – June 12, 2020

All waters in nature, whether rain water or ocean water, contain dissolved mineral salts. Salinity is the term used to define the total content of dissolved salts in sea water. Factors affecting ocean salinity are mentioned below:

• The salinity of water in the surface layer of oceans depends mainly on evaporation and precipitation.
• Surface salinity is greatly influenced in coastal regions by the fresh water flow from rivers, and in Polar Regions by the processes of freezing and thawing of ice.
• Wind, also influences salinity of an area by transferring water to other areas.

The ocean currents contribute to the salinity variations. Salinity, temperature and density of water are interrelated. Hence, any change in the temperature or density influences the salinity of water in an area.

About 71 per cent of the planetary water is found in the oceans. The remaining is held as freshwater in glaciers and icecaps, groundwater sources, lakes, soil moisture, atmosphere, streams and within life.

Storm Surge.

• Storm surge is the abnormal rise in seawater level during a storm, measured as the height of the water above the normal predicted astronomical tide.
• The surge is caused primarily by a storm’s winds pushing water onshore.
• The amplitude of the storm surge at any given location depends on the orientation of the coast line with the storm track;

The intensity, size, and speed of the storm; and the local bathymetry.

Sponges have been around for a very long time, with certain species having a fossil record that dates back approximately 600 million years to the earliest (Precambrian) period of Earth’s history.

The approximately 8,550 living sponge species are scientifically classified in the phylum Porifera, which is comprised of four distinct classes:

• the Demospongiae (the most diverse, containing 90 percent of all living sponges),
• Hexactinellida (the rare glass sponges),
• Calcarea (calcareous sponges), and
• Homoscleromorpha (the rarest and simplest class, only recently recognized, with approximately 117 species).

While sponges, like corals, are immobile aquatic invertebrates, they are otherwise completely different organisms with distinct anatomy, feeding methods, and reproductive processes. The main differences are:

• Corals are complex, many-celled organisms. Sponges are very simple creatures with no tissues.

All corals require saltwater to survive. While most sponges are found in the ocean, numerous species are also found in fresh water and estuaries.

Oceanic and atmospheric Rossby waves — also known as planetary waves — naturally occur largely due to the Earth’s rotation. These waves affect the planet’s weather and climate.

• Waves in the ocean come in many different shapes and sizes.
• Slow-moving oceanic Rossby wavesare fundamentally different from ocean surface waves.
• Unlike waves that break along the shore, Rossby waves are huge, undulating movements of the ocean that stretch horizontally across the planet for hundreds of kilometers in a westward direction.
• They are so large and massive that they can change Earth’s climate conditions.

Along with rising sea levels, King Tides, and the effects of El Niño, oceanic Rossby waves contribute to high tides and coastal flooding in some regions of the world.

In 1865, the Danish geologist and mineralogist Johan Georg Forchhammer, with the help of naval and civilian collaborators, collected numerous samples of seawater from the Northern Atlantic and the Arctic Ocean. He wanted to determine why the salinity (or “saltiness”) of seawater varies in different areas of the ocean.

• Forchhammer put the samples through a detailed series of chemical analyses and found that the proportions of the major salts in seawater stay about the same everywhere.
• This constant ratio is known as Forchhammer’s Principle, or the Principle of Constant Proportions.
• In addition to this principle, Forchhammer is credited with defining the term salinity to mean the concentration of major salts in seawater.
• Forchhammer’s discovery helped scientists understand that salinity levels in seawater vary due to the addition or removal of fresh water, rather than differing amounts of salt minerals in the water.

The principle is still applied today in marine research, and provides a simple way to estimate salinity and trace the mixing of water masses in the global ocean.

Population growth in different parts of the world can be compared. The growth of population is low in developed countries as compared to developing countries. There is negative correlation between economic development and population growth.

The transhumant system is prevalent in the Himalayas, where there are several nomadic tribes, such as the Gujars, Bakarwals, Gaddis and Changpas, who rear sheep and goats under this system.

• The animals are moved to subalpine and alpine pastures during summer, while during winter they are grazed on adjoining plains.
• The scale of this enterprise is widespread and is practised by a variety of farmers, including landless and marginal farmers, who have adopted this profession for earning a livelihood.
• Sale of wool and live animals for meat is their only source of income. The transhumant system is practised in order to locate the best herbage resources from pastures and grasslands.
• There are also well recognized pastoral tribes who practise a complete transhumance, moving from one place to another on traditional migratory routes.
• The dates of migration have traditionally been fixed. Even grazing rights rest with the migratory graziers by traditional usage, though they do not hold proprietary rights over the land.

The transhumant system is prevalent in the Himalayan region. However, this system still exists in some states situated in the plains, such as Rajasthan, Madhya Pradesh, Tamil Nadu, Gujarat and Uttar Pradesh.

Primitive subsistence agriculture or shifting cultivation is widely practised by many tribes in the tropics, especially in Africa, south and Central America and south East Asia.

The vegetation is usually cleared by fire, and the ashes add to the fertility of the soil. Shifting cultivation is thus, also called slash and burn agriculture.

It is prevalent in tropical region in different names, e.g. Jhuming in North eastern states of India, Milpa in Central America and Mexico and Ladang in Indonesia and Malaysia.

Collective farming.

• The basic principle behind collective farming is based on social ownership of the means of production and collective labour.
• Collective farming or the model of Kolkhozwas introduced in erstwhile Soviet Union to improve upon the inefficiency of the previous methods of agriculture and to boost agricultural production for self-sufficiency.

The farmers used to pool in all their resources like land, livestock and labour.