Ancient Earth's Magnetic Field Weakness: Key to Complex Life Evolution?

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Earth's magnetic field is essential for creating a habitable environment on our planet. This protective bubble shields Earth from solar radiation, winds, cosmic rays, and extreme temperature changes.

Earth’s magnetic field nearly collapsed 591 million years ago, but surprisingly, this event may have been crucial for the development of complex life, according to recent research.

John Tarduno, a geophysics professor at the University of Rochester in New York and the lead author of the study, explained that the magnetic field is typically protective. Without it in the early stages of Earth's history, water could have been stripped away by the solar wind, a flow of energized particles from the sun towards Earth.

This ancient brick has an inscription associated with Mesopotamian king Adad-Nirari I.

This ancient brick has an inscription associated with Mesopotamian king Adad-Nirari I.

Matthew D. Howland

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Ancient bricks from the time of King Nebuchadnezzar II absorbed a surge in Earth's magnetic field.

In the Ediacaran period, there was a fascinating time in the Earth's development when the processes that created the magnetic field became so inefficient after billions of years that the field almost completely collapsed.

A recent study, published in the journal Communications Earth & Environment on May 2, revealed that Earth's magnetic field was weaker than it is now for at least 26 million years. This magnetic field is generated by the movement of molten iron in Earth's outer core. The discovery of this prolonged weakening also helped solve a long-standing geological puzzle regarding the formation of Earth's solid inner core.

This period of weakened magnetic field coincides with the Ediacaran era, a time when the first complex animals appeared on the seafloor. This era also saw an increase in the percentage of oxygen in both the atmosphere and the ocean.

During this time, the Earth was home to some strange creatures that looked very different from the ones we see today. Some had soft bodies shaped like fans, tubes, or doughnuts, like Dickinsonia, which could grow up to 4.6 feet (1.4 meters) in size. There was also a slug-like creature called Kimberella.

Before this period, most life on Earth was made up of single-celled organisms that were too small to see without a microscope. Scientists think that a weak magnetic field might have caused an increase in oxygen in the air, which allowed more complex forms of life to develop.

A cast of a Dickinsonia costata fossil, dating back to 560 million years ago, was discovered in South Australia. This creature, which measures over a meter in length, is the largest known animal from that time period.

A photograph shows a cast of a 560 million-year-old Dickinsonia costata fossil found in South Australia. At more than a meter in length, the creature is the largest known animal from that period.

Shuhai Xiao/Virginia Tech

Uncovering the magnetic field’s near collapse

The Earth's magnetic field strength can vary over time, and crystals found in rocks hold a history of these changes through tiny magnetic particles trapped within them.

In 2019, a study of rocks in Quebec dating back 565 million years revealed that the Earth's magnetic field was ten times weaker during that time compared to its current strength, providing the earliest evidence of a significant weakening during that period.

The most recent research gathered additional geological evidence showing a significant weakening of the magnetic field. This evidence comes from 591 million-year-old rock found in southern Brazil, indicating that the field was 30 times weaker in the past compared to its strength today.

Royalty free 3d rendering of a photorealistic earth with a slice cut out. Realistic illustration with visible core.

Royalty free 3d rendering of a photorealistic earth with a slice cut out. Realistic illustration with visible core.

fpm/E+/Getty Images

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The team discovered that the weak magnetic field we see today was not always like this. They studied rocks from South Africa that were over 2 billion years old and found that the Earth's magnetic field was actually as strong as it is now during that time.

According to Tarduno, at that time, the innermost part of the Earth was not solid but liquid. This influenced the way the magnetic field was produced.

"According to him, over billions of years, this process is becoming less and less efficient. As we reach the Ediacaran period, the magnetic field is almost collapsing, reaching its weakest point. However, luckily for us, the inner core started to cool down and generate, strengthening the magnetic field."

The earliest complex life that emerged and floated along the seafloor is linked to an increase in oxygen levels. Some animals like sponges and microscopic creatures can survive with low oxygen levels, but larger animals with more complex bodies that move require more oxygen, according to Tarduno.

According to study coauthor Shuhai Xiao, a professor of geobiology at Virginia Tech, the rise in oxygen during this period is traditionally credited to photosynthetic organisms like cyanobacteria. These organisms produced oxygen, allowing it to gradually accumulate in the water over time.

The new research proposed a different idea about why hydrogen may have been lost to space when the geomagnetic field was weak.

Xiao explained via email that the Earth's magnetosphere protects the planet from solar wind, which helps keep the atmosphere in place. So, if the magnetosphere is weaker, lighter gases like hydrogen could escape from the Earth's atmosphere.

Tarduno mentioned that several processes could have been occurring simultaneously.

He added, "We do not dispute that one or more of these processes were happening at the same time. However, the weak magnetic field may have enabled oxygen levels to reach a critical point, which could have supported the evolution of animals."

Peter Driscoll, a staff scientist at the Earth and Planets Laboratory at the Carnegie Institution for Science in Washington, DC, shared his thoughts on the study's findings regarding Earth's magnetic field. He mentioned that while he agreed with the weakness of the magnetic field, he found it challenging to assess the claim that it could have impacted atmospheric oxygen levels and biological evolution. Driscoll clarified that he was not part of the study.

In an email, Driscoll explained that he struggled to determine the validity of the claim due to the limited understanding of how planetary magnetic fields could influence climate.

Tarduno expressed confidence in their hypothesis, but establishing a direct connection could be a lengthy and difficult process due to the limited knowledge about the creatures from that era.

A 565 million-year-old fossil of an Ediacaran animal, called Fractofusus misrai, was found at the Mistaken Point Formation in Newfoundland, Canada.

A 565 million-year-old fossil of an Ediacaran animal, called Fractofusus misrai, was found at the Mistaken Point Formation in Newfoundland, Canada.

Shuhai Xiao/Virginia Tech

Inner core mystery

The geological analysis also revealed telling details about the innermost part of Earth’s center.

Estimates used to vary on when the Earth's inner core solidified, with some suggesting it happened between 500 million to 2.5 billion years ago.

However, recent research on the Earth's magnetic field intensity indicates that the inner core likely solidified more recently, after 565 million years ago. This event allowed Earth's magnetic shield to recover and become stronger.

Driscoll mentioned that the observations seem to back up the idea that the inner core formed shortly after this period. This event helped to transition the geodynamo, which generates the magnetic field, from being weak and unstable to a strong and stable dipolar field.

Tarduno suggested that the strengthening of the magnetic field following the Ediacaran period, due to the growth of the inner core, likely played a crucial role in preventing Earth from becoming dry and water-deprived.

The strange animals of the Ediacaran era had vanished by the time the Cambrian Period arrived. This was when life on Earth experienced a sudden burst of diversity, leading to the development of the branches of the tree of life that we recognize today.

Editor's P/S:

The article explores the fascinating connection between Earth's magnetic field and the development of complex life on our planet. Researchers have discovered that the magnetic field nearly collapsed around 591 million years ago, coinciding with the emergence of the first complex animals. This weakened field may have allowed an increase in atmospheric oxygen, providing a crucial environment for the evolution of these early organisms. The study suggests that the magnetic field's protective role against solar radiation and atmospheric loss may have been a key factor in shaping the course of life on Earth.

The article also sheds light on the formation of Earth's solid inner core. By analyzing the magnetic field intensity of rocks, scientists have estimated that the inner core solidified more recently than previously thought, around 565 million years ago. This event strengthened the magnetic field, stabilizing it and preventing Earth from becoming dry and water-deprived. The interplay between the magnetic field and the inner core's formation highlights the intricate processes that have shaped our planet's history and made it habitable for complex life to thrive.