Major Domains of the Earth Part 1 << Learners Hobby

PHYSICAL REALMS
    Continents and oceans are the two main divisions of the Earth's surface. Three-fourths of the Earth's surface is covered by water in the for of oceans, seas, lakes and rivers. The three realms of the earth are:
1. Lithosphere (land) : The Lithosphere comprises the rocks of the Earth's crust and thin layer of soil that contains life sustaining nutrients.
2. Hydrosphere (water) : The Earth's hydrosphere consists of water available i various water bodies such as oceans, seas, rivers, lakes, underground water, glaciers, snow or as water vapour. All the oceans of the world are connected. They are separated and linked by continents.
3. Atmosphere (air) : The atmosphere provides life sustaining gases like oxygen and nitrogen. Plants do not use nitrogen directly from the atmosphere; their roots absorb it from the soil. This is just one example of interaction and inter-dependence of these domains.
INTERACTING REALMS
Biosphere (life) : Biosphere represents life on Earth, be it in water, on soil, under the soil or in the air. The narrow zone of contact between land, air and water is called biosphere. In recent years, the biosphere together with its physical environment has also been termed as Ecosphere. The ecosphere, though actually biosphere., shows some ecological factors like climate and vegetation which influence the biosphere.
    The three realms and the biosphere establish and inter-relationship and are interdependent on each other in the ecosphere. The give-and-take relationship between the realms goes on endlessly.
FORMATION OF LANDFORMS

    Various processes like weathering, nitrogen cycle, etc., take place  because of their interaction. It also sometimes leads to the formation of spectacular landforms. Of these processes the forces acting in the interior of the Earth produce first degree landforms like mountains and plateaus, explained subsequently.
    The interior of the Earth has three chief layer known as the crust, the mantle and the core. The continents and oceans rest on the crust. The mantle is the thickest of all layers. The lower mantle remains in a semi-molten condition. The molten rocks with gases and steam known as magma moves and finds its way up through cracks and fissures in rocks. The magma generates convection currents in the interior of the Earth. These currents have broken the earth's crust into small blocks, called plates. The movements of these plates as well as magma has produced fold mountains like Himalayas and Andes. The molten material when driven out on the surface is called lava. Many landforms, especially volcanic mountains, are made up of layers of lava. Below the mantle, lies the core. The core is composed of 80% iron along with some percentage of nickel and other light elements.
EXTERNAL FORCES
    The external forces are a result of a climate and interaction of its components - temperature and wind. These external forces are - weathering and erosion together known as denudation. Whereas changes like raising and lowering of landforms is always sudden. The changes on account of external forces are always aimed at lowering of these landforms.
PANGAEA

Millions of years ago, there was only one super-continent called Pangaea and one super-ocean called Panthalassa. On account of buoyancy and convection currents rising from semi-molten rocks under the lithosphere, the continent keeps moving. Cue to geological changes over several million years, the sole continent split into many small and big rocks of land called plates.
FLOATING CONTINENTS
    The evolution of continents and oceans is a continuous process as a result of movements of plates in different directions. The forces responsible for the movement of plates are :
1. Extremely hot interior of the earth which melts the rock and gives rise to movements of plates.
2. The forces of buoyancy of ocean water provides additional momentum to oceanic plates in a similar manner as happens to a boat.
EVOLUTION

    The parts of lithosphere are not only affected by movements indifferent directions but also by their emergence or submergence in and out of water in oceans. The process of evolution of Earth's land masses is based on certain events. Presently, the earth is divided into 7 major continents and 4 large oceans.
CHANGE
    Change is the property of nature. The present configuration will change in future gradually. The future earth 50 millions years hence is depicted. As per the current geological studies, large parts of the Earth will sink below the present sea level. The levels of some parts of the present oceans will fall and land will be exposed as landmasses. The Pacific Ocean will become smaller in size and the Atlantic will become large. The Australian continent will move closer to the equator. In this way, the dynamic Earth maintains the balance of its crust.