Astro-physicists and scientists believe that there could be
quite a few planets in the Universe similar to our planet
Earth. There is also a probable chance that some form of
life prevails and sustains in one of such planet.
However, so far as we presently know, the Earth is the only
planet which supports life which makes it a very unique
planet. It is therefore imperative (very important and
necessary) for us to understand the spheres of the Earth as
the spheres play a crucial role to enable life forms to
evolve, prevail and sustain.
The three main components of the Earth are water, air and
soil. They are not only in contact with each other but are
also interactive and interdependent. Life exists only where
these three components interact.
The Earth’s system consists of four major subsystems.
They are known as domains, spheres or realms. They are
the Lithosphere (land), Hydrosphere (water), Atmosphere (air) and Biosphere (the parts of the Earth where life is found, including land, water and the lower part of the atmosphere). LITHOSPHERE: the realm of land & MAJOR LANDFORMS
The Lithosphere is the solid surface layer of the Earth. It is generally referred to as the crust. It consists of all the land masses on the surface of the Earth. The surface of the Earth is very uneven. There are: High mountains, e.g., the Himalayas, the Rockies, the Andes, the Alps. Vast plains, e.g., the great plains of India, USA and Brazil. Deep valleys.
The two main features on the Earth’s surface are the continents and oceanic basins. Continents are large, distinct land masses usually separated by vast water-bodies (oceans and seas). There are seven major continents in the world. They are Asia, Africa, Europe, North America, South Ame rica, Australia and Antarctica. Most of the land masses lie in the Northern Hemisphere. The Southern Hemisphere has relatively fewer land masses.
Collectively, the land masses are known as the lithosphere. The lithosphere consists of different types of landforms. Landforms are features that make the Earth’s surface. The different types of landforms include mountains, plateaus, hills, valleys, plains, Ocean bed, sea bed, etc. How are the landforms formed? How are they useful to humans? The surface of the Earth constantly undergoes changes due to the action of various forces. It is essential to understand these forces and how they affect the landforms?
Internal forces are also known as endo-genetic forces or tectonic forces. Internal forces act from within the Earth that lead to sudden changes on the face of the Earth. The crust of the Earth is actually divided into several pieces which we call plates. These plates float over liquid molten rock called magma which lies below the solid crust. The core of the Earth heats the molten magma. The molten magma layer is called the mantle, which is in
between the core and crust. Due to the intense activity within the core and the mantle the magma often rises upwards when heated. It spreads, cools and then sinks back again, to get heated and rise once more. This constant rising and sinking of the magma keeps pushing the plates that rest on it. Thus, the plates are also constantly moving. This movement of the plates is termed as plate tectonics. Sometimes the plates move towards each other, or converge. Sometimes the plates move away from each other, or diverge. Sometimes, the plates slide by each other in a transverse movement.
Plate tectonics is responsible for the formation of mountains and valleys o n the surface of the Earth. These features can take millions of years to form. However, sometimes, sudden and strong movements take place within the Earth, which bring about massive changes on the surface of the Earth. Examples are the changes brought about on earth’s surface by the earthquakes, volcanoes, landslides, etc. External forces
External forces or gradational forces are forces acting from...