From UPSC perspective, the following things are important :
Prelims level : Drift of Indian plate from Gondwanaland
Mains level : History of Indian Monsoon
Using leaf fossils, researchers have found that the Indian monsoon 25 million years ago resembled present-day Australia’s.
Try this PYQ:
Q.Which one of the following is the appropriate reason for considering the Gondwana rocks as the most important rock systems of India?
(a) More than 90% of limestone reserves of India are found in them
(b) More than 90% of India’s coal reserves are found in them
(c) More than 90% of fertile black cotton soils are spread over them
(d) None of the reasons given above is appropriate in this context
- About 180 million years ago, India separated from the ancient supercontinent Gondwana and took a long northward journey of about 9,000 km to join Eurasia.
- During this journey, the subcontinent moved from the southern hemisphere, crossed the Equator to reach its current position in the northern hemisphere.
- Due to these changing latitudes, it experienced different climatic conditions, and a new study has now tried to map these climatic variations using leaf fossils.
Clueless over the evolution of monsoon
- The evolution of the monsoonal climate in India is still debatable and not fully understood.
- Though recent data indicates that the monsoon system we experience now dates back to about 25 million years, it is still unclear how the climate was during its long voyage.
- The researchers analysed the morphological characters of fossil leaves collected from Deccan Volcanic Province, East Garo Hills of Meghalaya, Gurha mine in Rajasthan and Makum Coalfield in Assam.
- The four fossil assemblages were found to be from four different geological ages.
- It has been observed from across the globe that plant leaf morphological characters such as apex, base and shape are ecologically tuned with the prevailing climatic conditions.
- The research applied this model to characterize the past monsoon from fossil leaves.
- The results indicated that the fossil leaves from India were adapted to an Australian type of monsoon and not the current Indian monsoon system during its voyage.
- The reconstructed temperature data show that the climate was warm (tropical to subtropical) at all the studied fossil sites with temperatures varying from 16.3–21.3 degrees C.
- All the fossil sites experienced high rainfall, which varied from 191.6 cm to 232 cm.