Tamil Nadu generally evokes images of its verdant paddy fields, ancient temples, and the peaceful Bay of Bengal coastline. But did you know that the state is also home to a desert unlike any other in India?
Hidden in the districts of Thoothukudi and Tirunelveli lies Theri Kaadu — a red sand marvel spanning approximately 500 square kilometres.
This unique terrain is distinguished by its striking crimson dunes, shaped by time and the relentless forces of nature. The vibrant red hue of the sand, attributed to its high iron oxide content, sets it apart from other arid landscapes in the country. But how did this extraordinary desert come to be?
The geological origins of Theri Kaadu
Theri Kaadu’s formation is a tale woven through millennia, dating back to the Quaternary Period. Literally translating to ‘red dune forest’, it is believed that the desert’s origins lie in a complex interplay of marine deposits and aeolian (wind-driven) processes.
During the Last Glacial Maximum, around 10,000 years ago, sea levels were significantly lower, revealing an extensive sea shelf. “Over time, strong winds carried iron-rich sediments from this exposed shelf and the Western Ghats, depositing them along Tamil Nadu’s southeastern coast,” says Dr Christy Nirmala Mary, head of the Department of Soil and Environment at the Agricultural College and Research Institute, Madurai. The gradual accumulation of these sands gave rise to the rolling dunes that define Theri Kaadu today.
Despite its desert-like conditions, Theri Kaadu is not a traditional desert formed by prolonged aridity. “Theri Kaadu formed by red ferruginous soil is a product of shifting sands and aeolian material, which is wind-transported and deposited,” says Dr Christy.
These geological imprints indicate that the area was once submerged under the sea, reinforcing the dynamic nature and marvel of Earth’s landscapes.
What makes Theri Kaadu unique?
Unlike vast deserts such as the Thar, Theri Kaadu is relatively small, yet its composition is fascinating. The desert is categorised into three distinct types based on its proximity to the coastline:
- Inland Theris: These dunes are located farthest from the sea and are relatively stable.
- Near Coastal Theris: Situated between inland and coastal regions, these dunes experience moderate movement due to wind and human activity.
- Coastal Theris: The most dynamic of the three, these dunes are continually reshaped by strong southwest winds, creating a landscape in constant motion.
“One of the most captivating aspects of Theri Kaadu is the ceaseless movement of its sands, making it a recently formed and unweathered soil,” says Dr Christy. Unlike other sandy terrains, where dunes remain relatively fixed, these red sands shift continuously, creating an ever-evolving topography.
This phenomenon makes the desert a natural wonder, challenging scientists and geologists to unravel its mysteries.
A natural laboratory for scientific exploration
Theri Kaadu serves as an invaluable natural laboratory for studying desertification, climate change, and soil composition. “Theri soil is sandy and coarse-textured and has very little clay content, making it difficult to understand the different horizons or layers,” adds Dr Christy.
Researchers use cutting-edge techniques such as luminescence dating to determine the age of the dunes and trace environmental transformations over thousands of years. These studies provide crucial insights into how climatic shifts influence landscapes and inform conservation strategies to combat desertification in other regions.
The iron oxide-rich sand not only gives Theri Kaadu its distinctive red hue but also impacts soil fertility. While some areas remain barren, certain resilient plant species have adapted to the harsh conditions, creating micro-ecosystems within the dunes.
“These ferruginous soils contain minerals like haematite, magnetite, limonite and the like, which are primarily iron-containing elements. This is reflected in the 2.5 YR soil colour according to the Munsell Soil Colour System,” shares Dr Christy.
The red desert is also home to species like velvet poochi (insect), fan-throated lizard, spotted owlets, and Eurasian kestrel, to name a few. Trees like palm, cashew, and a few shrubs are also present, but drought makes the vegetation challenging.
“The infiltration rate (the ability of water to seep through the soil) is very rapid in Theri soil, making it difficult to irrigate and grow crops like paddy. Using an irrigation technique named drip fertigation, where fertilisers are mixed with water, vegetation is possible, but it is heavy on the cost aspect,” says Dr Christy, forcing farmers to stick to the native trees.
This delicate balance highlights the intricate relationship between nature and survival, making the desert an essential subject of ecological research.
An example of Earth’s ever-changing face
Theri Kaadu is more than just a patch of red sand in the heart of Tamil Nadu; it is living proof of Earth’s dynamic history. From its origins in the Quaternary Period to its ongoing transformation by natural forces, this enigmatic desert holds secrets waiting to be uncovered.
Whether studied for its scientific relevance or admired for its breathtaking beauty, Theri Kaadu remains a hidden gem, urging us to look beyond conventional landscapes and embrace the wonders that nature has sculpted over time.
As we venture into the future, the responsibility lies with us to ensure that this geological marvel is not lost to neglect or reckless development. By fostering awareness and encouraging sustainable exploration, we can preserve Theri Kaadu for generations to come — a silent yet profound witness to Earth’s ever-evolving narrative.
Edited by Arunava Banerjee.
