1500 years from now Earth's magnetic field may be reversed

The north pole of the Earth's magnetic field is changing and getting weaker and weaker. The ancient lava flow gives us a deeper understanding of the causes of the development and control of the Earth's magnetic field, as well as what can cause a magnetic field to change direction.

The main magnetic field is generated by strong currents in the molten iron block deep in the outer core of the Earth. The magnetic field changes periodically and the compass needle points south, not just north. The phenomenon of polar exchange has occurred hundreds of times with an uneven interval between the Earth's historical course. The last time was about 780,000 years ago, but scientists still try to understand how and why.

The study of ancient volcanic rock published in the September 26 issue of Science shows that there is a second magnetic field source that determines how and whether the main magnetic field has a positive change. The second magnetic field originates from the shallow core just below the Earth's mantle. It plays an important role when the main north-south magnetic field weakens before reversing, according to Brad Singer, a professor of geology at the University of Wisconsin-Madison.

He teamed up with planetary magnetic field researcher Kenneth Hoffman - who has been studying magnetic field reversals for more than 30 years - to analyze ancient flow flows from Tahiti and western Germany to Learn the type of Earth's magnetic field in the past. The magnetism of iron-rich minerals in molten lava follows the existing magnetic field, which will be trapped in places where lava cools and hardens.

Singer said: 'When the lava flow erupted and cooled, they brought back the memory of the earth's magnetic field at that time. It is very difficult to destroy lava flow once it has formed. At that time we will have a record of magnetic field on Earth '.

The polarity phenomenon has occurred hundreds of times with an uneven time between two times throughout the Earth's history, the last time being 780,000 years ago.But scientists are still trying to understand how and why.(Photo: iStockphoto / Tobias Machhaus)

Hoffman, an expert at California Polytechnic University (San Luis Obispo) and University of Wisconsin - Madison, and Singer, focused on studying rocky soil with evidence of weak north-south magnetic fields. This is a sign that polarization can be reversed. By determining the age of the lava flow, they can map from the shallow core field during the reversals when the main field weakens in the past few million years.

At that time, the weakened main field revealed 'ultra-virtual' or strong magnetic fields belonging to the shallow core field. For example, Singer said, 'If you are in Tahiti when lava erupts, your compass needle is not only to the North Pole, nor to the South Pole, but to Australia.'

Scientists believe that the shallow core field may play a role in determining whether the polarity of the main magnetic field changes while weakened; and whether it can restore its intensity without reversing. According to Hoffman, 'mapping from a shallow core field during transitions holds the key to understanding what happens in Earth's core when the field is so weak that it can reverse'.

Current evidence suggests that we are moving toward one of those transitions because the Earth's main magnetic field is quite weak and declining. While the most recent polarization reversal occurred hundreds of thousands of years ago, the next time may happen within a few thousand years.

Singer said: 'Right now, historical records show that the intensity of the magnetic field is declining rapidly. As expected, within 1500 years the magnetic field will be the weakest and we will enter the polarization reversal. Our major research goal is to provide the ability to predict what will happen and what could be the signal of the upcoming polarization reversal. '

Hoffman and Singer's research is funded by the National Science Foundation.