Summary of "UGC NET JUNE 2024 Geography Paper 2 लक्ष्य JRF Demo class By Dr. Shikha Sharma"

Summary of the Video:

UGC NET JUNE 2024 Geography Paper 2 लक्ष्य JRF Demo class By Dr. Shikha Sharma

Main Topic: Continental Drift Theory

Key Concepts and Lessons:

Introduction to Continental Drift and Landform Orders:
- Earth formed after the Big Bang, cooled down, leading to formation of first-order landforms: continents and oceans.
- Landforms are categorized into three orders:
  - First order: Continents and oceans (major landforms).
  - Second order: Mountains, rivers, plains, plateaus.
  - Third order: Landforms shaped by water, wind, glaciers (valleys, etc.).
- Continental drift explains the origin of continents and oceans (first order landforms).
Historical Development of Continental Drift Theory:
- Abraham Ortelius (1596) was the first to propose ideas related to continental drift.
- Lothian Green proposed the Tetra Hydal hypothesis related to continental displacement.
- Taylor (1908-1910) also contributed to the theory.
- Alfred Wegener (1912) formulated the most comprehensive displacement hypothesis, initially as a hypothesis, later proven as a theory post-1960.
- Wegener’s theory was published in German and translated into English in 1924, gaining wider recognition afterward.
Wegener’s Hypothesis and Evidence:
- Wegener reviewed climatologists' works and noticed climate change over geological time.
- Two possibilities considered:
  - Climatic belts moved, continents remained stationary.
  - Continents moved, climatic belts remained stable (Wegener supported this).
- Wegener lacked knowledge of plate tectonics and plate movements, which were confirmed later (post-1960).
Earth’s Structure According to Suess and Wegener:
- Earth’s layers: Sial (continental crust), Sima (mantle), Nife (core).
- Sial (continental crust) floats over Sima (semi-molten upper mantle) with little friction, allowing movement.
- This floating explains continental drift.
Supercontinent Pangaea and Panthalassa Ocean:
- Pangaea was a supercontinent surrounded by a super ocean called Panthalassa.
- Pangaea split into Laurasia (north) and Gondwana (south).
- India was part of Gondwana, explaining coal deposits.
- The breakup led to the formation of modern continents and oceans.
- The “Third Sea” formed from the breakup became the Pacific Ocean.
- Geosynclines formed during this process contributed to the origin of the Himalayas.
Evidence Supporting Continental Drift:
- Jigsaw Fit: Coastlines of South America and Africa fit together like puzzle pieces.
- Similar Rock Structures and Mountain Ranges: Geological structures and mountain systems (Caledonian and Hercynian) in South America, Africa, North America, and Europe are similar.
- Fossils and Vegetation: Same fossils and plant species (e.g., Glossopteris) found across continents now separated by oceans.
- Glaciation Evidence: Similar glacial deposits found in India, South Africa, Australia, Antarctica, Brazil, and other places, despite current different climates.
- Animal Behavior (Lemmings): Lemmings’ migration patterns suggest land connection where there is now ocean.
- Shift of Greenland: Greenland shifts westward by 20 cm/year, confirming plate movement.
Forces Behind Continental Drift:
- Two main types of continental movements:
  - Movement towards the equator (north or south).
  - Movement towards the west.
- Forces involved:
  - Gravitational Force: Pulls towards Earth’s center.
  - Buoyancy Force (Bansi): Opposes gravity, keeps continents floating on semi-molten mantle.
  - Balance between gravity and buoyancy allows continents to float and move.
  - Tidal Forces: Caused by the moon and sun, contribute to westward movement.
- Earth's shape (oblate spheroid) influences these forces and continental drift.
Timeline and Period of Displacement:
- Wegener suggested displacement started in the Carboniferous period.
- Displacement caused continents to break away from polar regions due to centrifugal force.
- Formation of fold mountains like the Rockies, Andes, Alps, and Himalayas resulted from continental collisions.
- Island arcs and island chains (e.g., Kamchatka, Philippines) formed due to plate movements.