Q. Consider the following statements:

  1. The Earth’s magnetic field has reversed every few hundred thousand years.
  2. When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
  3. When living organisms orginated, they modified the early atmosphere of the Earth.

Which of the statements given above is/are correct?

  • 1 only
  • 2 and 3 only
  • 1 and 3 only
  • 1, 2 and 3

Answer: (c) 1 and 3 only

Notes:

  • Scientists estimate reversals have happened at least hundreds of times over the past three billion years.
  • Over the last 20 million years, magnetic north and south have flipped roughly every 200,000 to 300,000 years.
  • The last of these major reversals occurred about 780,000 years ago.
  • Between 4.5 and 2.5 billion years (the Archaean and Proterozoic time), the earliest secondary atmosphere contained carbon dioxide (CO2), methane (CH4), water vapor (H2O), carbon monoxide (CO), a little nitrogen (N), and hydrogen (H). So Carbon dioxide is present.

Also Read: Origin of Atmosphere