450 million years ago the earth’s magnetic field almost collapsed – the consequences would have been apocalyptic

More than the half A billion years ago, Earth experienced an almost total collapse of its magnetic field. It started in the early Cambrian. Then, after about 15 million years, the field started growing again. The cause of this collapse and field recovery was a mystery. Then a group of geologists studied Oklahoma rocks formed during this period. Magnetic markers in the rock’s minerals pointed to an event that began about 550 million years ago. This was before the introduction of multicellular life to our planet.

Look deep into the core

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 right now reading this. Below that is the mantle, the thickest layer on Earth. It overlies the molten outer core surrounding the solid inner core. This inner core consists of two parts – an outermost inner core and an innermost inner core. The core region is approximately 2900 kilometers below the surface. The whirling motion of liquid iron in the outer core creates 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 basically happened? Why did our magnetic field decay to almost 10 percent of its strength and then regenerate? According to John Tarduno, a professor of geophysics at the University of Rochester in New York, the cause was the formation of the Earth’s solid inner core.

“The inner core is hugely 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 regenerated.”

Paleomagnetism shows changes in our magnetic field

In a recent paper, Tarduno and a team of researchers cited crucial dates in the history of the inner core. They also gave an accurate age estimate for collapse and regeneration. Since they can’t reach into the core and observe it directly, how did they find out when these events happened? The team turned to paleomagnetism to find an answer. That’s the study of magnetic markers in rocks that were created as rocks formed. Geologists often use this to keep track of other changes in the Earth’s magnetic field, such as B. reversing the poles.

The 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 extreme temperatures of the materials in the core. So geologists thought of a better way. They looked for paleomagnetic markers in rocks and minerals that rose to the surface. These marks are like tiny needles that determine the direction and intensity of the magnetic field that was present as the minerals cooled after they were formed.

Tarduno and his team set out to determine the age and growth of Earth’s inner core using paleomagnetism to measure these particles. So they used a CO2 laser and a SQUID magnetometer (superconducting quantum interference device) to analyze feldspar crystals from the rock anorthosite and study their perfect magnetic markers.

Dating rocks with magnetism for victory

By examining the magnetism trapped in these ancient crystals, the researchers determined two new important dates. The first was when the magnetic field began to strengthen after nearly collapsing 15 million years ago. This rapid regrowth was due to the formation of a solid inner core. In fact, it recharged the molten outer core and restored the strength of the magnetic field.

Another interesting thing happened about 450 million years ago. Then the structure of the growing inner core changed. The result was a border between the innermost and the outermost inner core. Mantle changes occurred far above the core due to plate tectonics on the surface.

According to Tarduno, paleomagnetism has enabled this new understanding of the Earth’s core. “Because we were able to narrow down the age of the inner core, we were able to examine the fact that today’s inner core actually consists of two parts,” he said. “Plate tectonic movements on the Earth’s surface indirectly affected the inner core, and the history of these movements is imprinted deep within the Earth in the structure of the inner core.”

What about magnetic fields elsewhere?

The team’s research on paleomagnetic clues to Earth’s internal evolution provides clues to the history and evolution of our planet. It also offers a glimpse of how it became habitable. Finally, their work has implications for understanding the evolution of other planets in the solar system. Things could well be different if they didn’t have magnetic fields. For example, Mars once had a magnetic field, but that dissipated more than 4 billion years ago. This made the planet vulnerable to the solar wind and likely played a role in the loss of Martian oceans.

It’s not clear if Earth would have suffered the same fate if its magnetic field hadn’t regenerated. Tarduno said our planet would have lost a lot of water if the magnetic field hadn’t returned. “The planet would be much drier and very different than the planet today,” he pointed out. “This research really underscores the need to have something like a growing inner core that sustains a magnetic field throughout the lifespan – many billions of years – of a planet.”

This article was originally published on universe today through Carolyn Collins Petersen. Read the original article here.