- By no means is the explanation of the process that caused the red hills definitive. Other theories suggest that the main cause of the formation is mainly due to "Fluvial" meaning action caused by flowing water. And that it happened in a period of tectonic quiescence - a quiet period without too much tectonic activity.
- Yet others are convinced that much of what we see today is due to the "Neotechtonic" activity, this fancy word simply means tectonic activity that took place in the recent past, which is around 6,000 years ago.
- It has been pointed out that the sudden change in the flow of the Gosthani River, the gap in the Bhimunipatnam ridge, the pattern of fractures and several other clues clearly indicate a series of recent tectonic activities.
- It is possible that the theories converge at a point to explain the surreal "Erra matti dibbalu" landscape, but the jury is still out on the exact process that caused these formations.
- That is why it is even more important that these dunes be preserved in its original form for future generations to study and to admire.
- Some scientists are of the opinion that the initial chapter of this epic story took place in the "Pleistocene" period from around 1.8 million years ago to around 10,000 years ago.
- During that time the sea level rose to as much as 50 meters above the current level and fell away below the current level many times.
- Between these oscillating sea levels the coast was submerged and exposed over and over again. When the sea receded it left behind huge volumes of clay and silt.
- Subsequently, the beach sand swept over the clay and silt, and over time this "Aeolian" (carried by wind) sand covered the earlier soil forming large sand dunes.
- The clay and silt under the sand then "baked" in the sun much like a brick gets baked in a kiln leading to the peculiar red earth. Later, action of the wind and flowing water caused the deeply gullied characteristic landscape. The red colour of the dunes is said to be due to the "ferrogination" of "haemitite".
- This simply means that iron rich material haemitite coated the loose sand grains and when it got exposed to the elements the stuff oxidized over a period of time. Just like a nail exposed to salty air would get corroded and appear red in colour.
- The Erra Matti Dibbalu, which resemble a mini-Grand Canyon and are just about 28 kilometers away from Vizag city.
- Erra Matti Dibbalu mean Red Mud Hillocks in Telugu. Popularly known as the Red Soil Hills, these natural ravines spread extensively in various formations – some jagged, some deep, some maze-like and some creating walls along trekking pathways – thanks to recurring wind currents and soil erosion.
- Said to be over a million years old, they comprise sand, clay and silt and are acknowledged as a rare geographic phenomenon.
- They are also favorite location spots for film shootings and for tourists.
- On the Bay of Bengal coast, to the south of the Bhimunipatnam ridge, is an area comprising deeply gullied red sand dunes of around 4 km length and 2 km width.
- It is bounded by streams "Chittigadda" in the North-West and "Peddagadda" in the South-West.They are unique because of the gullied red dunes formations.
