Order of Relief

Various kind of relief feature can be seen on earth and ocean surface. Large scale landscapes can be divided into three orders of relief called Mega relief.

Megareliefs include the largest landscapes by scale, from enormous ocean basins and continents down to local hills, spurs, cliffs, valleys, gorges and river terraces. Accordingly, there are three orders of relief as follows:

First Order Relief

·         Entire lithosphere which consists of continental crust as well as the oceanic crust comes under first order relief.

·         Continental crust has lower density than the oceanic crust and is made up of granitic rock consisting of Silica and Aluminium predominantly. While oceanic crust is made up of basaltic rocks and majorly consists of Silica and Magnesium.

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Second Order Relief

·         Consists of all endogenic forces which originate from within earth's crust/surface. Endogenic forces are responsible for developing variations on the surface of the earth, hence they are also known as variability developers.

·         Can be Grouped into:     

1.      Diastrophism==> mountain building forces is responsible for the development of blocks as well as Fold Mountains.

2.      Volcanism/Earth quakes.

Mountains are the best example of product of endogenic processes on continental crust. While submarine ridges (formed due to solidification of magma) and trenches forms the best example in oceanic crust.

Third order relief:

·         This type of relief basically consists of exogenic forces. Exogenic forces are those forces which originate on the surface of the earth. These forces are:

1.      Running water.

2.      Wind.

3.      Underground water.

4.      Glacier.

5.      Sea waves

·         The third order of relief includes individual peaks, cliffs, valleys, hills, spurs, gorges, sand dunes, caves, moraines, cirques, ripples, beaches, etc. These features are identified as local landscapes