Using satellite observations and field visits, two independent researchers from France have identified eight sites around Jaisalmer in the Thar Desert, that show linear features resembling geoglyphs.
What are geoglyphs?
- Geoglyphs are large, un-explained geometrical patterns on land usually proposed to be man-made features.
- The largest concentration of geoglyphs is reported from southern Peru, covering an area of about 1,000 square km.
- A new paper published notes that the identified geoglyphs in the Thar Desert cover an area of about 6 square km.
Boha Geoglyphs in Thar
- The authors’ main area of interest was Boha, a small village 40 km to the north of Jaisalmer where they noticed a series of concentric and linear features.
- They named these features Boha geoglyphs and suggested that the features could be at least 150 years old.
- It is however conceivable that they were built at the beginning of the British colonial period, in the middle of the 19th century.
How are they patterned?
- The Boha geoglyphs are clearly manmade as the main unit is a giant spiral, but they have been eroded due to the cars running over the lines lately.
- So, they are clearly not formed by weathering or another natural phenomenon.”
- The observed features might have been formed naturally, but degraded over time due to both natural and human-related causes.
Degraded over time
- The rocky terrain is home to a typical weathering feature, especially over the iron-rich sandstone and shale beds.
- Here, extreme aridity and high temperature lead to slow geochemical translocation of minerals for centuries, such that the heavier minerals like iron and manganese move away from the lighter minerals.
- This lead to the gradual formation of alternate bands of harder and softer mineral concentrations.
- With time the areas with softer materials get slowly eroded, while the harder ones stand out, producing the typical concentric or box-like geometric features.
