Desert In Tamil Nadu

Gs Paper-1

Syllabus: Geomorphology:

Context:

Recent news has highlighted the desert in Tamil Nadu. It has dunes that are red. The red dunes are called theri in Tamil. They consist of sediments dating back to the Quaternary Period and are made of marine deposits.

Features of the dunes:

• They have very low water and nutrient retention capacity.
• The dunes are susceptible to aerodynamic lift.
• Reason for Red colour: The iron-rich heavy minerals like ilmenite, magnetite, garnet, hypersthene, and rutile present in the soil had undergone leaching by surface water and were then oxidized because of the favourable semi-arid climatic conditions giving them distinct red colour.

Theories behind their formation:

Theory 1: The present-day theris might have been formed by the confinement of beach sand locally, after the regression of the sea. When high-velocity winds from the Western Ghats blew east, they induced migration of sand grains and accumulation of dunes.

Theory 2: Another view is that these are geological formations that appeared in a period of a few hundred years.

Theory 3: The red sand is brought from the surface of a broad belt of red loam in the plains of the Nanguneri region by southwest monsoon winds during May-September.

• The southwest monsoon winds, after draining the moisture behind the Mahendragiri hill and the Aralvaimozhi gap of the Western Ghats, become dry and strike the plains in the foothills, where vegetation is sparse. This churns red loam and is driven east in huge columns of red sand, till they are met by sea breeze near the coastal tract of Tiruchendur and get deposited there.
• The sand deposited thus also forms a further obstruction, causing more sand to be deposited and the process goes on. Thus, in the due course of time, a dune is formed.

Source: Down To Earth