More than half A billion years ago, the Earth experienced an almost complete collapse of its magnetic field. It began in the early Cambrian period. Then, after a period of about 15 million years, the field began to grow again. The reason for this collapse and return of the sphere was a mystery. Then a group of geologists studied the rocks from Oklahoma that were created during that time. Magnetic signs in the minerals of the rocks indicated an event that began about 550 million years ago. That was before multicellular life appeared on our planet.
Deep insight into the essence
To understand what happened, look at the structure of our planet. Most of us learn in school that the Earth is made up of layers. There’s the crust where you’re sitting reading this right now. Beneath it is the mantle, the Earth’s thickest layer. It is located above the molten outer core, which surrounds the solid inner core. This inner core consists of two parts – an inner outer core and an inner inner core. The core area is located about 2,900 km below the surface. The swirling action of liquid iron in the outer core is what generates our magnetic field. Without this activity, we would not have a protective shield against the solar wind. In fact, without it, our planet might be more like Mars today.
So, what happened to the core? Why did our magnetic field fade to about 10 percent of its strength and then regenerate again? According to John Tarduno, a professor of geophysics at the University of Rochester in New York, the reason was the formation of the Earth’s solid inner core.
“The inner core is very important,” he said. “Just before the inner core started growing, the magnetic field was about to collapse, but as soon as the inner core started growing, the field was renewed.”
Ancient magnetism reveals changes in our magnetic field
In a recent research paper, Tarduno and a team of researchers report crucial dates in the history of the inner core. They also provided an accurate estimate of the age of collapse and regeneration. Since they could not reach and directly observe the heart, how did they find out when these events occurred? The team turned to ancient magnetism to find an answer. This is the study of magnetic signs in rocks that were created when rocks formed. Geologists often use this to keep track of records of other changes in the Earth’s magnetic field, such as a pole flip.
Earth’s magnetic field extends from the core through the mantle and crust into space. It is impossible to directly measure the magnetic field inside the Earth. This is due to the location and temperature extremes of the materials in the core. Therefore, geologists thought of a better way. They searched for ancient magnetic signs in the rocks and minerals that rose to the surface. These marks are like tiny needles sticking out in the direction and intensity of the magnetic field that was present when the minerals cooled after they were formed.
Tarduno and his team wanted to determine the age and growth of Earth’s inner core by using ancient magnetism to measure those particles. Therefore, they used a carbon dioxide laser and a superconducting quantum interference device (SQUID) to analyze feldspar crystals from anthocyanic rocks and study their ideal magnetic signs.
Dating rocks using magnetism to win
By studying the magnetism enclosed in those ancient crystals, researchers have identified two important new histories. The first was when the magnetic field began to strengthen after collapsing nearly 15 million years ago. This rapid growth was due to the formation of a solid inner core. It had already recharged the molten outer core and restored the strength of the magnetic field.
Another interesting thing happened about 450 million years ago. That’s when the structure of the growing inner core changed. The result was a boundary between the innermost and outermost core. Above the core, changes in the mantle have occurred due to plate tectonics at the surface.
Ancient magnetism made this new understanding of the Earth’s core possible, according to Tarduno. “Since we constrained the age of the inner core more precisely, we can explore the fact that the current inner core actually consists of two parts,” he said. “The movements of the tectonic plates on the Earth’s surface indirectly affected the inner core, and the history of these movements is imprinted deep inside the earth in the structure of the inner core.”
What about magnetic fields elsewhere?
The team’s research into ancient magnetic clues to Earth’s internal evolution provides clues about the history and evolution of our planet. It also provides insight into how it became habitable. Finally, their work has implications for understanding the evolution of other planets in the solar system. Things could be completely different if they didn’t have magnetic fields. For example, Mars once had a magnetic field, but it dissipated over 4 billion years ago. This left the planet vulnerable to the solar wind and likely played a role in the loss of Mars’ oceans.
It is not clear whether Earth would have met the same fate if its magnetic field had not been renewed. Tarduno said our planet would have lost a lot of its water if the magnetic field had not returned. “The planet will be drier and will be much different from the planet today,” he noted. “This research really highlights the need for something like a growing inner core that maintains the magnetic field for the lifespan – many billions of years – of a planet.”
This article was originally published on universe today by Caroline Collins Petersen. Read the original article here.