Monthly archives: September, 2020

Shape and size of Earth

Earth is a planet of the Solar system which revolves around the Sun at a distance of 149.6 million Kilometres. Earth is shaped like a ball. It is not a perfect sphere but an oblate spheroid or a ball flattened at the poles with a slight bulge at the center (equator). Photographs taken from space …

Common Radiometric Methods

1. Potassium-Argon Method: Potassium-40 has a half life of 11900 million years. It is commonly found in many rocks. It decays into argon-40, and inert gas found in the sedimentary rocks. Potassium-Argon method can be used to date rocks that are millions of years old, including meteorites(age 4600 million years). However rocks younger than 0.1 …

Radiometric Dating.

The methods of radiometric dating are based on the radioactive decay of certain isotopes that have very long half-lives. The radioactive isotope is often referred to as the “parent” and the elements resulting from the decay of parent are called the “daughter products”. The age of rocks and minerals that contain radioactive isotopes is determined …

Subsistence Farming

Subsistence Farming (agriculture) is defined as the farming which is carried out in small scale and with low technology. It aims at food production for local consumption of family or community and not for trade purpose. Thus, this types of agriculture does not have any surplus production. Mostly the shifting cultivators are subsistence farmers. Like …

Features of Migratory Primitive Agriculture.

Main features of the migratory primitive agriculture include the following: Human labor and hand implements are used only. Land is cleared with the help of fire. Draft animals are not used. Fertilizers are not used. Land belongs to community. Members of community can use as much land for cultivation as they like. The production is …

Definition and types of Agriculture.

Definition: Agriculture is defined as the purposeful tending of crops and livestock in order to produce food and fiber. According to another definition, agriculture includes all productive efforts which are undertaken by man to expedite the growth of vegetable and animal products for the benefit of man. Types of Agriculture: Agricultural practices can be classified …

History of Economic System

Historical past has witnessed the development and decay of many economic systems. The ancient and medieval economies have gradually given rise to several economic systems which reflect the political, social and economic requirements of particular social set ups. Ancient and Medieval Economics: In ancient and medieval times, the scope of the economic systems was limited …

Importance of Malthusian Theory of Population.

Despite all the criticism, the Malthusian theory is very important in the annals of human geography. Undoubtedly it has highlighted the disadvantages of over population. In the views of Thompson, “Malthus deserves great credit for bringing this problem to the attention of people as well as for the calm and objective manner in which he …

Criticism of Malthusian Theory of population

The Malthusian theory is based on law of diminishing returns because he could not foresee the future. Presently the food supply is being increased by using advanced scientific methods. It is wrong to presume that the sexual urge in human beings remains unchanged. The fact is that the urge is reduced as a result of …

Age of the Earth

The age of the earth as determined by current methods of radiometric dating is about 4600 million years. Before the discovery of radiometric dating several attempts were made to determine the age of the earth. The important one’s are as follows. From history of organic evolution. From rate of sedimentation. From salinity of sea water. …