depiction of the Earth, first without an inner core; second, with the beginning of inner core growth, about 550 million years ago; Third, with a deeper outer and inner core, about 450 million years ago. University of Rochester researchers used paleomagnetism to determine these two important dates in the history of the inner core, which they believe restored the planet’s magnetic field before life on Earth exploded. Credit: University of Rochester Photography/Michael Osadio
–
New ancient magnetic research shows that Earth’s dense core formed 550 million years ago and brought back our planet’s magnetic field.
The rotation of molten iron in Earth’s outer core, which lies about 1,800 miles below our feet, creates a protective magnetic field for our planet, called magnetosfer. Although this magnetic field is invisible, it is essential for life on Earth’s surface. This is because the magnetosphere protects the planet from the solar wind – a stream of radiation from the sun.
However, about 565 million years ago, the strength of the magnetic field decreased to 10% of its current strength. Then, mysteriously, the magnetic field bounced back, regaining its strength before the Cambrian explosion of multicellular life on Earth.
What causes the magnetosphere to bounce?
This renewal occurs within a few tens of millions of years, according to new research by scientists at the University of Rochester. This is very fast on geological timescales and coincides with the formation of the Earth’s dense core, suggesting that the core is likely a direct cause.
“The inner core is very important,” said John Tarduno, professor of geophysics in the Department of Earth and Environmental Sciences and dean of arts, science and engineering research at Rochester. “Just before the inner core started growing, the magnetic field almost collapsed, but as soon as the inner core started growing, the field was renewed.”
In a paper published on July 19, 2022 in the journal NAthor TelecomHowever, scientists have identified several important dates in the history of the deep core, including a more accurate estimate of its age. This research provides new clues about Earth’s history and future development and how it became a habitable planet, as well as the evolution of other planets in the solar system.
Earth’s layers and structures.
–
Unlock information in ancient rocks
Earth is made up of layers: the crust where life exists; mantle, thick layer of the earth; The outer core is liquid and the inner core is solid, which in turn consists of an outer inner core and a deeper inner core.
Earth’s magnetic field is created in its outer core. The circulation of molten iron there causes an electric current, which leads to a phenomenon called geodynamo that generates a magnetic field.
Due to the relationship of the magnetic field to the Earth’s core, scientists have been trying for decades to determine how the magnetic field and the Earth’s core have changed throughout the history of our planet. They cannot directly measure the magnetic field due to the location and extreme temperature of the material in the core. Fortunately, minerals that rise to Earth’s surface contain tiny magnetic particles that lock in the direction and intensity of the magnetic field as the mineral cools and solidifies from its molten state.
To further limit 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 laboratory to analyze feldspar crystals from anorthosite rock. This crystal has a tiny magnetic needle inside which is an “ideal magnetic recorder,” Tarduno said.
By studying magnets trapped in ancient crystals – a field known as palaeomagnetism – researchers have identified two important new dates in the history of deep nuclei:
- 550 million years ago: The time when the magnetic field began to rapidly regenerate after collapsing approximately 15 million years earlier. The researchers attribute the rapid regeneration of the magnetic field to the formation of a solid inner core that replenishes the liquid outer core and restores the strength of the magnetic field.
- 450 million years ago: The time when the structure of the growing inner nucleus changes, indicating the boundary between the inner and outer nuclei. These deep core changes coincided with near-simultaneous changes in the upper shelf structure, due to plate tectonics at the surface.
“Because we more precisely defined the age of the inner core, we were able to explore the fact that the current inner core actually consists of two parts,” Tarduno said. “The movement of tectonic plates at the Earth’s surface indirectly affects the inner core, and the history of this movement is imprinted deep within the Earth in the structure of the inner core.”
Avoid fate like Mars
A better understanding of the dynamics and growth of the inner core and magnetic field has important implications, not only in uncovering Earth’s past and predicting its future, but also in uncovering and sustaining conditions under which other planets might form magnetic shields. harbor life.
Para peneliti percaya bahwa[{”attribute=””>MarsforexampleoncehadamagneticfieldbutthefielddissipatedThatlefttheplanetvulnerabletosolarwindandthesurfaceoceanlessWhileitisunclearwhethertheabsenceofamagneticfieldwouldhavecausedEarthtomeetthesamefate“Earthcertainlywould’velostmuchmorewaterifEarth’smagneticfieldhadnotbeenregenerated”Tardunosays“Theplanetwouldbemuchdrierandverydifferentthantheplanettoday”[{”attribute=””>MarsforexampleoncehadamagneticfieldbutthefielddissipatedThatlefttheplanetvulnerabletosolarwindandthesurfaceoceanlessWhileitisunclearwhethertheabsenceofamagneticfieldwouldhavecausedEarthtomeetthesamefate“Earthcertainlywould’velostmuchmorewaterifEarth’smagneticfieldhadnotbeenregenerated”Tardunosays“Theplanetwouldbemuchdrierandverydifferentthantheplanettoday”
In terms of planetary evolution, then, the research emphasizes the importance of a magnetic shield and a mechanism to sustain it, he says.
“This research really highlights the need to have something like a growing inner core that sustains a magnetic field over the entire lifetime—many billions of years—of a planet.”
Reference: “Early Cambrian Renewal of the Geodynamo and the Origin of Inner Core Structure” by Tinghong Zhou, John A. Tarduno, Francis Nimmo, Rory D. Cottrell, Richard K. Bono, Mauricio Ibanez-Mejia, Wentao Huang, Matt Hamilton, 1999; Kenneth Kodama, Alexei V. Smirnov, Ben Crummins and Frank Padgett III <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
DOI: 10.1038/s41467-022-31677-7
–