Geophysical phenomena -PLATE TECTONICS THEORY

• 300 Mya – two great landmasses

• Laurasia – N.P

• Gondwanaland – S.P. – India (without the Himalayas) ; S. America ; Africa ; Australia.

• 200 Mya – Gondwanaland broke up and the land masses started drifting.

• India – moved northward – position across the equator about 50 Mya.

• Movement – further northward and collided
with northern Asia which gave rise to the present Himalayan mountains.

• Indian climate – Monsoon type .

• Evolution of monsoon climate in India is not fully understood.

• Monsoon – a tropical phenomenon

• First appeared –entering the subtropical belt of the southern hemisphere .

• Research – monsoon system dates back to about 25 million years.
• Fossil leaves : morphological characters were analyzed
 Deccan Volcanic Province
 East Garo Hills of Meghalaya
 Gurha mine in Rajasthan
 Makum Coalfield in Assam collected.

• Fossils – different geological ages like 65, 57,
54, and 25 Mya.

• Note : Morphological characters of leaves get
altered according to the prevailing weather
and climatic conditions.

Study of the fossil leaves.

• Dated back – 65, 57, 54, and 25 Mya .

• Adapted – Australian type of monsoon and not the current Indian monsoon system.

• Fossil sites had warm climates – 16.3–21.3 degrees C.

• High rainfall between 191.6 cm to 232 cm

• India – only subcontinent to have crossed from the southern hemisphere to the northern hemisphere.

• Aim – better understanding
 Evolution of Indian monsoons
 Role in the evolution of biodiversity hot spots
⮚ Help in the conservation of modern biodiversity hot spots
⮚ The future monsoon prediction