Coastal Red Sand Dunes

• 03 Dec 2022

For Prelims: Erra Matti Dibbalu, Geologic Time Scale, Quaternary Period, Geologic Time Scale.

For Mains: Significance of studying Coastal Red Sand Dunes.

Why in News?

Recently, geologists have suggested to protect the site of Coastal Red Sand Dunes, of Visakhapatnam, Andhra Pradesh.

What are the Key Points of the Sites?

• About:
  • The Coastal Red Sand Dunes is also known as ‘Erra Matti Dibbalu’. It is one of the many sites of Visakhapatnam, which have geological importance.
  • The site is located along the coast and is about 20 km north-east of Visakhapatnam city and about 4 km south-west of Bheemunipatnam.
  • This site was declared as a geo-heritage site by the Geological Survey of India (GSI) in 2014 and the Andhra Pradesh government has listed it under the category of ‘protected sites’ in 2016.
• Distribution:
  • Such sand deposits are rare and have been reported only from three places in the tropical regions in south Asia such as Teri Sands in Tamil Nadu, Erra Matti Dibbalu in Visakhapatnam and one more site in Sri Lanka.
  • They do not occur in equatorial regions or temperate regions due to many scientific reasons.

What is the Uniqueness of these Sediments?

• Continuous Evolution:
  • The red sediments are a part of the continuation of the evolution of the earth and represent the late quaternary geologic age.
    • The Quaternary Period is a period on the Geologic Time Scale that's known mainly for the spread of humanity and climate change. This period runs from about 2.6 million years ago to the Present Day.
• Different Geomorphic Features:
  • With a height of up to 30 m, they exhibit badland topography with different geomorphic landforms and features, including gullies, sand dunes, buried channels, beach ridges, paired terraces, the valley in the valley, wave-cut terrace, knick point and waterfalls.
    • Badland topography is a dry terrain where softer sedimentary rocks and clay-rich soils have been extensively eroded by wind and water.
• Geochemically Unaltered:
  • The top light-yellow sand unit, which is estimated to have been deposited around 3,000 years ago, could not attain the red colouration as the sediments were geochemically unaltered.
  • These sediments are unfossiliferous (not containing fossils) and deposited over the khondalite basement.
    • Khondalite is a regional rock with high-grade metamorphism and granulite rock formation. It was named after the Khond tribe of Odisha.

What is the Significance of Protecting this Site?

• It is significant to protect this site, because its study can help understand the impact of climate change, as Erra Matti Dibbalu has seen both the glacial and the warm periods.
• The site is about 18,500 to 20,000 years old and it can be related to the last glacial period.
• It is a lively scientific evolution site, which depicts the real-time effects of climate change.
  • About 18,500 years ago, the sea (Bay of Bengal) was at least 5 km behind from the present coastline. Since then, it has been undergoing continuous active changes till about 3,000 years ago and still the changes are on.
• The site also has archaeological significance, as studies of artifacts indicate an Upper Palaeolithic horizon and on cross dating assigned to Late Pleistocene epoch, which is 20,000 BC.
• The site was home to the pre-historic man as the excavations at several places in the region revealed stone implements of three distinctive periods and also the pottery of the Neolithic man.

Source: TH