Our planet Earth has not always been like it is now. During the billions of years since the Earth was formed, there have been episodes of ice ages, extinctions, changes, reversals, cycles, etc. It is never fixed and so stable.
One of the things that have changed and that has not been like this all our life is the Earth's magnetic pole. About 41.000 years ago, the Earth had a reversed polarity, that is, the north pole was the south and vice versa. Do you want to know why this happens and how scientists know?
Inversion in the magnetic pole of the Earth
Throughout the history of the Earth, changes in the magnetic poles have occurred repeatedly, lasting hundreds of thousands of years. In order to know this, scientists rely on tests with minerals that respond to magnetic stimuli. That is, by analyzing the alignment of magnetic minerals, it is possible to know what orientation the Earth's magnetic poles had millions of years ago.
But it is no longer only important to show that the magnetic poles of the Earth have been changing throughout history, but why they have done so. Scientists have found Giant lava lamps that have rock spots that periodically rise and fall deep into our planet. The action of these rocks can cause changes in the Earth's poles and cause them to flip. To find this, the scientists based their studies on signals left by some of the most destructive earthquakes on the planet.
Almost at the edge of the Earth's core there is a temperature of 4000 ° C so that the solid rock gradually flows over millions of years. This current of convection in the mantle causes the continents to move and change shape. Thanks to the iron that is formed and maintained in the Earth's core, the Earth maintains its magnetic field that protects us from solar radiation.
The only way for scientists to know this part of the Earth is by studying the seismic signals generated by earthquakes. With the information of the speed and intensity of the earthquake waves they can know what we have under our feet and what composition there is.
Is there a new model of the Earth?
With this way of studying the Earth, it can be known that there are two large regions in the upper part of the Earth's core where seismic waves travel more slowly. These regions are quite relevant in terms of how they affect the entire mantle dynamics, in addition to conditioning the way in which the core cools.
Thanks to the strongest earthquakes in recent decades those that make possible the study of these waves that travel through the boundary between the core and the Earth's mantle. The latest research on these regions of the Earth's interior shows how the lower part of the core has a higher density (hence the lower part) and the upper part a much lower density. This suggests something quite important. And it is that the materials are increasing on the surface, that is, they are moving upwards.
Regions can be less dense simply because they are warmer. As with air masses (the hottest tends to rise), something similar happens within the mantle and core of the Earth. However, it is possible that the chemical composition of the mantle parts is behaving like the drops of a lava lamp. That is to say, first they heat up and with that they rise up. Once up, having no contact with the core of the Earth, it begins to cool and become denser, so it slowly descends back to the core.
This lava lamp-like behavior would change the way scientists explain the extraction of heat from the surface of the core. In addition, it can perfectly serve to explain why, throughout the history of the Earth, the magnetic poles have been reversed.
Full study: http://www.sciencedirect.com/science/article/pii/S0012821X15000345