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.

The Big Bang is the cosmological model of the initial conditions and subsequent development of the Universe that is supported by the most comprehensive and accurate explanations from current scientific evidence and observation.

As used by cosmologists, the term Big Bang generally refers to the idea that the Universe has expanded from a primordial hot and dense initial condition at some finite time in the past (currently estimated to have been approximately 13.7 billion years ago), and continues to expand to this day.

Georges Lemaître proposed what became known as the Big Bang theory of the origin of the Universe.

A subcontinent is part of a larger continent, made up of a number of countries that form a large mass of land.
The countries forming the Indian Subcontinent are Bangladesh, Pakistan, Nepal, and Bhutan.

A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are generally found where tectonic plates are diverging or converging and most are found underwater. 

From Gujarat to Arunachal Pradesh there is a time lag of two hours. Hence, time along the Standard Meridian of India (82° 30' E) passing through Mirzapur (in Uttar Pradesh) is taken as the standard time for the whole country. Otherwise different regions of India would have different times which would create problems; so, to have one common standard times for the whole country has been selected and called Indian Standard Time (IST).

GULF - a deep inlet of the sea almost surrounded by land , with a narrow mouth is called a gulf . For example ,, Gulf of Mexico.....
STRAIT - a strait is a narrow passage of water connecting 2 large water bodies .For example ,, Bering Strait.

Some  of the states through which standard meridian passes are:

• Uttar Pradesh
• Madhya Pradesh
• Chattisgarh
• Orissa
• Andra Pradesh

The longitudinal gap between Arunachal Pradesh and Gujarat is about 30°. Due to this, there is time lag of about two hours between these states. Since Arunachal Pradesh is in the east hence the sun rises earlier here; compared to in Gujarat. The Indian Standard Time is taken from the time of Standard Meridian of India and hence the watches show the same time in both the states.

The hydrosphere is the combined mass of water found on, under, and above the surface of a planet, minor planet or natural satellite. Although the Earth's hydrosphere has been around for longer than 4 billion years, it continues to change in size. This is caused by seafloor spreading and continental drift, which rearranges the land and ocean.

1. Hydrosphere on the earth refers to the water domain in all the states: solid, liquid and gaseous.
2. It includes the water present in rivers, lakes, oceans, ice caps, and glaciers, etc.
3. It extends several kilometers below and above the earth’s surface.

Oceanography is the branch of science that deals with the physical and biological properties and phenomena of the sea.