Coastal red sand dunes of Vizag

About Coastal Red Sand Dunes-

• They are popularly known as ‘Erra Matti Dibbalu’.
• 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 spread across an area of about 20 sq km 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.
• Geologists say that this site has much significance geologically, archaeologically and anthropologically and it needs to be protected for further study and evaluation.
• Primarily this site needs to be protected to study the impact of climate change, as Erra Matti Dibbalu have seen both the glacial and the warm periods.
• According to geologists, the site is about 18,500 to 20,000 years old and it can be related to the last glacial period.
• 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.
• The uniqueness of this site is that the red sediments are a part of the continuation of the evolution of the earth and represent the late quaternary geologic age. 
• 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.
• 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 top light-yellow sand unit could not attain the red colouration as the sediments were geochemically unaltered. 
• These sediments are unfossiliferous and deposited over the khondalite basement. The dunes consist of light yellow sand dunes at the top followed by a brick red sand unit, a reddish brown concretion bearing sand unit with yellow sand at the bottom. 
• The earlier studies indicate that the bottom-most yellow sand unit is fluvial while the other overlying three units are aeolian in origin.
• The site also has archaeological significance, as studies of artefacts indicate an Upper Palaeolithic horizon and on cross dating assigned to Late Pleistocene epoch, which is 20,000 BC.
• Scientists say that 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.

Note: 

• A sand dune is any accumulation of sand grains shaped into a mound or ridge by the wind under the influence of gravity. 
• Sand dunes are comparable to other forms that appear when a fluid moves over a loose bed, such as subaqueous “dunes” on the beds of rivers and tidal estuaries and sand waves on the continental shelves beneath shallow seas. 
• Dunes are found wherever loose sand is windblown: in deserts, on beaches, and even on some eroded and abandoned farm fields in semiarid regions.