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 originated, they modified the early atmosphere of the Earth. Which of the statements given above is/are correct?

Question

GSMediumPrelims 2018Physical Geography

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?

Explanation

Statement 1 is correct. The Earth's magnetic field does reverse polarity every few hundred thousand years, on average.

Statement 2 is incorrect. The early Earth's atmosphere did not have significant oxygen and likely had a lot of carbon dioxide and other greenhouse gases.

Statement 3 is correct. The rise of photosynthetic organisms like cyanobacteria significantly increased the amount of oxygen in the atmosphere over time.

Therefore, the correct answer is (c) 1 and 3 only.