GEOGRAPHY OF THE WORLD | GEOGRAPHY CHAPTER 3 | SEBA NOTES | CLASS 10 |

 

1. Write in brief about the earth’s lithosphere and hydrosphere.  

 

A large portion of the earth’s surface covered by the oceans and seas including rivers, lakes, etc is known as the Hydrosphere. On the other hand, another part of the earth’s surface formed by land slightly above sea-level is called the Lithosphere.

The hydrosphere and lithosphere are penetrating within each other through fragmentation of both the units. The lithosphere is divided into four divisions. The first part of the lithosphere is formed by the continents of Asia, Europe and Africa; the second part is formed by the continents of North America and South America; the third part by Australia including a large number of islands constituting the continent of Oceania; and the fourth part by the continent of Antarctica. A large proportion of the hydrosphere (57per cent) is confined to the southern hemisphere.

On the other hand, among the five oceans of the earth, which are all interlinked and surrounding the continents, the Pacific is located between Asia, North America and South America; the Atlantic is located between North America and South America and Europe and Africa; the Indian ocean is located on the south of Asia, east of Africa and west of Oceania; the Northern or the Arctic Ocean on the north of North America, Europe and Asia; and the Southern ocean is on the south of South America, Africa and Oceania. A large portion of the lithosphere (67 per cent) is confined to the northern hemisphere.

 

2. How was the earth in the early days according to the Continental Drift Theory?

Answer: According to the Continental Drift Theory, in the early stage, that is about 300 million years before (Permian Period of Palaeozoic Era), the earth’s lithosphere was together as a single landmass, which was surrounded by hydrosphere. This state of the lithosphere of the earth is known as Pangaea, and the hydrosphere surrounding the Pangaea is known as Panthalassa. After the passage of some time, a narrow and elongated sea was formed due to fracture almost in the middle of the Pangaea in an east-west  direction. It is known as Tethys sea. Formation of this  Tethys sea divided the Pangaea into two parts in the  north-south direction. Its northern part is called  Angaraland or Laurasia and the southern part  Gondowanaland. During the Mesozoic era, that is  about 250 million years ago, due to splitting and  continental drift the Laurasia and Gondowanaland got  further divided and moved towards the equator. and  the west and thereby the continents of present form  were created. According to the theory of continental  drift, North America, Greenland and the landmass of  Europe and Asia north of Indian sub-continent were  formed after division of the Laurasia. On the other  hand, following the division of the Gondowanaland  South America, Africa,  Madagaskar, India, Arabian  region, Malayasia and its other islands, Australia,  Antarctica, etc were formed.