Consider the following statements:
- The Earth’s magnetic field has reversed every few hundred thousand years.
- When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
- When living organisms originated, they modified the early atmosphere of the Earth.
Which of the statements given above is/are correct?
[UPSC Civil Services Exam – 2018 Prelims]
(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3
Answer: (c)
Explanation:
- Scientists have determined that the Earth’s magnetic field has undergone reversals many times in the past three billion years, occurring approximately every 200,000 to 300,000 years in the last 20 million years.
- The most recent major magnetic reversal took place approximately 780,000 years ago.
- In the Archaean and Proterozoic era, between 4.5 and 2.5 billion years ago, the early atmosphere contained carbon dioxide, methane, water vapor, carbon monoxide, nitrogen, and hydrogen.
- When living organisms orginated, they modified the early atmosphere of the Earth.
Therefore, option (c) is the correct answer.
