Question

On the magnetic polarity time scale, the present-day epoch/chron is called _______.

• A. Matuyama
• B. Gilbert
• C. Gauss
• D. Bruhnes

Answer 1

The Correct Option is D

The concept of the "magnetic polarity time scale" refers to the record of the Earth's magnetic field reversals as captured over geological time in oceanic basalt formations. The term "chron" refers to a time period during which the Earth's magnetic field maintains a stable polarity. The present-day epoch's magnetic polarity is known by a specific name.

Let's evaluate the given options to identify the correct name for the current magnetic polarity epoch:

1. Matuyama: This is a reversed polarity chron that preceded the current normal polarity chron. It lasted from approximately 2.58 million to 0.78 million years ago.
2. Gilbert: This is an earlier reversed polarity chron that existed approximately between 4 million and 3.6 million years ago.
3. Gauss: This is a normal polarity chron that occurred before the Matuyama Chron, lasting from about 3.6 million to 2.58 million years ago.
4. Bruhnes: This is the current normal polarity chron, which has been in effect since approximately 780,000 years ago. It is named after the French scientist Bernard Brunhes.

Based on the above explanations, the correct answer to the question is the Bruhnes chron, as it is the current magnetic polarity epoch. The Bruhnes chron is associated with a normal or 'normal' magnetic polarity, meaning the magnetic north pole is near the geographic north pole.