Body waves travel through the interior of the Earth. On the other hand, surface waves propagate only at the interface between two different media, like the interface between Earth and atmosphere (i.e. the surface of the Earth).

A constellation is a group of stars that forms an imaginary outline or pattern on the celestial sphere, typically reprrepresen an animal, mythological person or creature, a god, or an inanimate object.
Ex: Leo - The Lion
Orion - The Hunter
Scorpius - The Scorpion

Differentiation can be defined as a derivative of a function regarding the independent variable and can be applied to measure the function per unit change in the independent variable.

Let y = f(x) be a function of x. Then, the rate of change of “y” per unit change in “x” is given by dy / dx

• The portion of the interior beyond the crust is called the mantle.
• It is in a solid state.
• It has a density higher than the crust portion.
• The thickness ranges from 10-200 km.
• The mantle extends from Moho’s discontinuity to a depth of 2,900 km.
• The asthenosphere is the upper portion of Mantle.
• It is the chief source of magma that finds its way to the surface during volcanic eruptions.
• The crust and the uppermost part of the mantle are called lithosphere.

Ecological balance is a state of dynamic equilibrium within a community of organisms in a habitat or ecosystem. It can happen when the diversity of living organisms remains relatively stable. Gradual changes do take place but that happens only through natural succession. It can also be explained as a stable balance in the numbers of each species in an ecosystem. This occurs through competition and cooperation between different organism s where the population remains stable. This balance is brought about by the fact that certain species compete with one another determined by the environment in which they grow. This balance is also attained by the fact that some species depend on others for their food and sustenance. Such accounts are encountered in vast grasslands where the herbivorous animals (deer, zebras, buffaloes, etc.) are found in plenty. 
Ecological balance may be disturbed due to the introduction of new species, natural hazards or human causes. Human interference has affected the balance of plant communities leading to disturbances in the ecosystems. Such disturbances bring about numerous secondary successions. Human pressure on the earth’s resources has put a heavy toll on the ecosystem. This has destroyed its originality and has caused adverse effects to the general environment. Ecological imbalances have brought many natural calamities like floods, landslides, diseases, erratic climatic occurrences, etc. There is a very close relationship between the plant and animal communities within particular habitats. Diversity of life in a particular area can be employed as an indicator of the habitat factor. Proper knowledge and understanding of such factors provide a strong base for protecting and conserving the ecosystems.

Mineral: naturally occuring inorganic substance having an orderly atomic structure and a definite chemical composition and physical properties.
It is composed of two or three minerals /single element ex. S,Cu, Ag,Au, Graphite.
There are at least 2000 minerals in the crust. There are at least six mineral groups which form rocks in the crust.
The basic source of all minerals is the hot magma in the interior of the earth. Coal, petroleum and natural gas are organic minerals

The time of a place depends on the longitude that passes through it. Therefore, the standard time for each country is usually taken as the time of the central meridian that passes through it. India has a vast longitudinal extent. Since many meridians pass through it, it is important to adopt the local time of one central meridian of a country as the standard time for the country.  Thus, we need a standard meridian for the country.  In India 82 ½ °E longitude determines the standard time. This is known as the Indian Standard Time. This longitude passes through Allahabad in Uttar Pradesh.

Physical geography includes the study of lithosphere (landforms, drainage, relief and physiography), atmosphere (its composition,structure, elements and controls of weather and climate; temperature, pressure, winds,precipitation, climatic types, etc.),hydrosphere(oceans, seas, lakes and associated features with water realm) and biosphere ( life forms including human being and macro-organism and their sustaining mechanism, viz. food chain, ecological parameters and ecological balance).

The study of physical geography is emerging as a discipline of evaluating and managing natural resources. In order to achieve this objective, it is essential to understand the intricate relationship between physical environment and human beings. Physical environment provides resources, and human beings utilise these resources and ensure their economic and cultural development. Accelerated pace of resource utilisation with the help of modern technology has created ecological imbalance in the world. Hence, a better understanding of physical environment is absolutely essential for sustainable development.

Ganga river

Earthquake waves get recorded in seismographs located at far off locations. However, there exist some specific areas where the waves are not reported. Such a zone is called the 'shadow zone'. The study of different events reveals that for each earthquake, there exists an altogether different shadow zone. Seismographs located at any distance within 105° from the epicentre, recorded the arrival of both P and S -waves. However, the seismographs located beyond 145° from the epicentre, record the arrival of P-waves but not that of S-waves. Thus, a zone between 105° and 145° from epicentre was identified as the shadow zone for both the types of waves. Figures given below show the shadow zones of P- and S-waves.

The entire zone beyond 105° does not receive S-waves. The shadow zone of S-wave is much larger than that of the P-waves. The shadow zone of P-waves appears as a band around the earth between 105° and 145° away from the epicentre. The shadow zone of S-waves is not only larger in extent but it is also a little over 40 per cent of the earth surface.

Geographers are important for any country because:

1. A geographer is someone who studies the earth and its land, features, and inhabitants. They also examine phenomena such as political or cultural structures as they relate to geography. 
2. They study the physical or human geographic characteristics or both of a region, ranging in scale from local to global. Some do fieldwork, which may include travel to foreign countries or remote locations.
3. They gather geographic data through field observations, maps, photographs, satellite imagery, and Censuses.
4. A geographer can overlay aerial or satellite images with GIS data, such as population density in a given region, and create computerized maps. They then use the results to advise governments, businesses, and the general public on a variety of issues, such as marketing strategies; planning homes, roads, and landfills; or disaster responses.
5. They study the variations and association of the features on the earth surface e.g., cropping pattern differs from place to place and it is due to difference in the climate, soil, demand, transport facility, capacity of the farmer.

The process through which the gases were outpoured from the interior is called degassing. Hydrogen and helium are among the gases which were outpoured from the interior of earth through degassing.