The Rock Record for Tens of Millions of Years Indicates

question 18

Multiple Choice

The rock record for tens of millions of years indicates that the Earth's magnetic field ____.

• A) reverses polarity about every 500,000 years
• B) is constant in strength and polarity
• C) did not come into existence until about 1 million years ago
• D) is a monopole magnet
• E) has steadily weakened and will be gone in another 10 million years