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 400

1. A. 1 only
2. B. 2 and 3 only
3. C. 1 and 3 only
4. D. 1, 2 and 3

Answer: C

Explanation

Statement 1 is correct: Earth’s magnetic field has flipped its polarity many times over the millennia. Magnetic Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a magnetic pole reversal about every 200,000 to 300,000 years. Statement 2 is not correct: When Earth formed 4.6 billion years ago, it had almost no atmosphere. As Earth cooled, an atmosphere formed mainly from gases spewed from volcanoes. It included hydrogen sulfide, methane, and 10 to 200 times as much carbon dioxide as today’s atmosphere. Statement 3 is correct: Living organisms includes plants and microbes. Life started to have a major impact on the environment once photosynthetic organisms evolved. While photosynthetic life reduced the carbon dioxide content of the atmosphere, it also started to produce oxygen. So, when living beings originated, they did modify the atmosphere.