NCERT Class 11 Geography Chapter 2: The Origin and Evolution of the Earth YouTube Lecture Handouts

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NCERT Class 11 Geography Part 1 Chapter 2: Origin & Evolution of Earth

Origin of Earth – Early Theories

  • Nebular Hypothesis - Kant & revised by Laplace
  • Chamberlain & Moulton – Cigar Shaped star - Planetesimal Theory
  • Jeans & Jefferys – Tidal Theory
  • Otto Schimdt – Dust Cloud (revised nebular hypothesis)
  • Early Theories of Origin of Earth

Origin of Earth – Modern Theories

Illustration: Origin of Earth – Modern Theories
Illustration: Origin of Earth – Modern Theories

Star Formation

  • Density difference lead to diff. in gravitational force
  • Galaxy – many stars – spread over many light years
  • Diameter of galaxy: 80,000 to 1,50, 000 light years (distance)

Planet Formation

  • Star localized in nebula – core & disc formed
  • Gas cloud condense around core – by cohesion – planetesimals
  • Planetesimal accrete to form planets

Solar System

  • Nebula collapsed 5 - 5.6 billion years ago
  • Planets formed 4.6 billion years ago
  • Inner or Terrestrial Planets (till Mars) – too warm for gas to condense, solar winds were intense, small & low gravity couldn՚t hold gas
  • Outer or Jovian or Gas Giant Planets: H & He
  • Solar System

Moon

  • Natural Satellite of earth
  • Darwin – earth & moon originated from single body – dumb-bell shaped body that broke

Evolution of Earth

Origin of Life

Origin of Live

Illustration: Origin of Life

Manishika