Phanerozoic Earth History

Key Questions

• How was the O-zone formed and why is it important for life on earth?

  Ozone is formed by the reaction of a oxygen molecule with a oxygen atom due to high UV radiation
  `3O_2rightleftharpoons2O_3`
  process is as
  `O_2->2O`(1)due to the energy of `UV`rays
  `2O_2+2Orightleftharpoons2O_3`(2)
  (1)-(2)
  `3O_2rightleftharpoons2O_3`
  It is imprtant for the life at higher altitudes as the it absorbs the UV rays and dont allow them to fall on earth
  at lower altitudes ozone is a harmful gas to the life on earth

  Dharma R. · 1 · Sep 22 2015

• What is Snowball earth, when did it occur, and what impact did it have on life on earth?
• What lifeforms characterize the Quaternary period?
• How was the O-zone formed and why is it important for life on earth?
• What are the major stages in the history of life on Earth?
• How was the Cretaceous period different from the Jurassic Period?
• What are the divisions of the geologic time scale?