This magnetic field is invisible but vital to life on Earth because it protects the planet from solar winds, which are streams of radiation from the sun.
New paleomagnetic research led by Rochester’s John Tarduno suggests Earth’s solid inner core formed 550 million years ago—and restored our planet’s magnetic field ???? ????#URochesterResearch | https://t.co/k69ArDJxRIpic.twitter.com/MrW2ybWhvr
— University of Rochester (@UofR) July 25, 2022
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About 565 million years ago, the strength of the magnetic field fell to 10% of its strength today. Then, mysteriously, the magnetic field bounced back, regaining its strength before the Cambrian explosion of multicellular life on Earth.
What caused the magnetic field to bounce?
According to new research by scientists at the University of Rochester, this regeneration occurred within a few tens of millions of years, which is fast on geological time scales.
It coincided with the formation of the Earth’s solid inner core, indicating that the core is likely a direct cause of this regeneration.
“The inner core is very important,” says John Tarduno, professor of geophysics in the Department of Earth and Environmental Sciences and dean of arts, sciences and engineering research at Rochester. “Just before the inner core started growing, the magnetic field was about to collapse, but as soon as the inner core started growing, it fell.” regeneration of the magnetic field.
Scientists have identified several key dates from the inner core’s history, including a more accurate estimate of its age. The research, published in the journal Nature Communications, provides clues about the history and future development of Earth and how it became a habitable planet, as well as the evolution of other planets in the solar system.
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The Earth consists of layers: the crust where life exists – the mantle, the thicker layer of the Earth – the molten outer core – the solid inner core, which in turn consists of an inner and outer core and a deeper inner core.
The Earth’s magnetic field originates in its outer core, where the rotation of liquid iron causes electric currents, which leads to a phenomenon called geodynamo that produces the magnetic field.
Because of the magnetic field’s relationship to the Earth’s core, scientists have been trying for decades to determine how the Earth’s magnetic field and core changed throughout the planet’s history.
The magnetic field cannot be measured directly due to the location and extreme temperatures of the materials in the core.
Fortunately, minerals that rise to Earth’s surface contain tiny magnetic particles that hold in the direction and intensity of the magnetic field as the minerals cool from their molten state.
To better determine the age and growth of the inner core, Tarduno and his team used a carbon dioxide laser and a superconducting quantum interference device (SQUID) in the lab to analyze feldspar crystals from anorthosite, which have tiny magnetic needles inside, which are “ideal magnetic recorders.”
By studying magnetism trapped in ancient crystals – a field known as palaeomagnetism, researchers have identified two important new dates in the history of the inner core:
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550 million years ago: The time when the magnetic field began to regenerate rapidly after nearly 15 million years of collapse before that. The researchers attribute the rapid regeneration of the magnetic field to the formation of a solid inner core that recharges the molten outer core and restores the strength of the magnetic field.
450 million years ago: The time when the structure of the growing inner core changed, indicating the boundary between the inner and outer core. These changes in the inner core coincide with changes at about the same time in the structure of the upper mantle, due to plate tectonics at the surface.
Tarduno explains: “Because 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. Movements of tectonic plates at 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 Earth’s surface. inner core”.
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A better understanding of the dynamics and growth of the inner core and magnetic field has important implications, not only in revealing Earth’s past and predicting its future, but also in revealing the ways in which other planets might form magnetic shields and maintain the conditions necessary to harbor life.
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Researchers believe that Mars, for example, once had a magnetic field, but that field dissipated, leaving the planet vulnerable to the solar wind and the surface without oceans.
While it is unclear whether the absence of the magnetic field would lead to Earth facing the same fate, according to the researchers, “It is certain that our planet would have lost a lot of water if the Earth’s magnetic field had not been renewed. Our planet would be drier and much different than it is today. “.
In terms of planetary evolution, the research emphasizes the importance of the magnetic shield and a mechanism for preserving it, says Tarduno.
He noted: “This research really highlights the need for something like a growing inner core that maintains a magnetic field for the lifespan – many billions of years – of a planet.”
Source: Science Daily