Scientists Suggest Complex Life Formed as A Result of Earth's Magnetic Field Almost Collapsing
It's pretty incredible what we can learn from rocks.
Hiya!
When radiation from the sun interacts with Earth’s magnetic field, the result is a visually spectacular show of swirling, colorful lights in the sky known as the Aurora Borealis or the Northern Lights. A solar storm a few weeks ago allowed people further south to see the remarkable show usually reserved for inhabitants of the planet’s far north. I, of course, slept right through it, only to kick myself in the morning for missing it.
The aurora borealis is a sight to behold, but it’s only one component of our planet’s magnetic field. Perhaps the most important feature is shielding us from harmful outside forces, which sustains life on Earth. Now, scientists believe Earth’s magnetic field is more than just responsible for protecting life on Earth; it may also have spurred Life to begin with.
Earth’s Magnetic Field
Earth’s rotation spurs the molten iron in its outer core into motion, creating a magnetic field around the planet. Research suggests Earth’s magnetic field is around 4 billion years old — or about as old as the planet itself — and creates a protective bubble encompassing Earth. This bubble keeps us at relatively stable temperatures while shielding us from cosmic radiation and solar winds and reducing the impact of ultraviolet radiation.
In other words, Earth’s magnetic field is a big reason our planet is habitable. That said, the magnetic field fluctuates over time, such as flipping the magnetic north-south every few hundred thousand years.
One way to gauge the field’s strength and how it has changed millions and billions of years ago is to test crystals preserved in rocks from that time. These crystals contain microscopic magnetic particles that record the planet’s magnetic field strength when the crystal is formed.
In 2019, research led by John Tarduno — the William R. Kenan, Jr., Professor of Earth and Environmental Sciences and Dean of Research for Arts, Sciences, and Engineering at the University of Rochester, New York — first utilized such methods to study 565 million-year-old rocks from Quebec and found evidence suggesting Earth’s magnetic field was ten times weaker back then compared to its strength today. By 591 million years ago, the field almost collapsed.
Ediacaran
You’re probably familiar with the Cambrian Period, also known as the Cambrian Explosion, which was between 541 million years ago and 485.4 million years ago when a massive burst of diverse and complex life evolved on Earth.
Well, the Ediacaran, which is when Tarduno suggests Earth’s magnetic field was weaker, set the stage for the Cambrian to shine. The Ediacaran lasted from about 635 million to 541 million years ago and is known for the massive amount of oxygen accumulated in Earth’s atmosphere and oceans during that time, which spurred the first multicellular, oxygen-using organisms to evolve.
Scientists had mostly agreed that as more organisms evolved photosynthesizing abilities, they created an oxygen surplus over the Ediancaran, which ignited the Cambrian explosion. But now, new research suggests another reason for the Ediancaran oxygen boom.
New Research
Tarduno, along with a collaborative team of scientists from the U.S. and Brazil, published another enlightening study in the journal Communications Earth & Environment in May 2024. This time, Taduno and his team found evidence suggesting Earth’s weakened magnetic field almost 600 million years ago aided the vital oxygen boost that spurred complex life across the planet.
Professor of geobiology at Virginia Tech and the study’s coauthor, Shuhai Xiao, explained to Katie Hunt of CNN,
“The magnetosphere shields the Earth from solar wind, thus holding the atmosphere to the Earth. Thus, a weaker magnetosphere means that lighter gases such as hydrogen would be lost from the Earth’s atmosphere.”
In other words, scientists believe lighter gases in Earth’s atmosphere 600 million years ago floated away because the magnetic field was too weak to contain them. Theoretically, this resulted in an abundance of free-floating oxygen atoms for organisms to use during the time.
To test their theory, the researchers built on Tarduno’s previous research and examined the microscopic crystals in feldspar rocks from southern Brazil and South Africa.
The analysis found that 591 million years ago, when the crystals in the Brazil rocks formed, Earth’s magnetic field was 30 times weaker than it is today. Yet, the magnetic field from 2 billion years ago, when the crystals in the South African rocks formed, was just as strong as today.
The researchers explain that when the South African rocks formed, Earth’s core hadn’t solidified yet. It was liquid that churned and released heat into the cooler mantle above it, coating molten iron around the core, which created the magnetic field.
By the time Ediacaran came around, the temperature differences in the Earth’s core had decreased, which slowed down the churning and consequently weakened the planet’s magnetic field. Tarduno explained to Hunt:
“By the time we get to the Ediacaran, the field is on its last legs. It’s almost collapsing. But then, fortunately for us, it got cool enough that the inner core started to generate [strengthening the magnetic field].”
Still, the scientists found that Earth’s magnetic field was weak for at least 26 million years before bouncing back to full strength. The study’s evidence of a prolonged field weakening also edges scientists closer to resolving a long-held geologic mystery.
Experts think Earth’s liquid core formed about 4 billion years ago, but when did the inner core become solid?
Bonus Discovery
Previous research estimated Earth’s inner iron core solidified between about 2.5 billion and 500 million years ago. The new analysis suggests the event happened toward the more recent end of the spectrum, around 565 million years ago.
The solidification of Earth’s inner core allowed the planet’s magnetic field to strengthen again, which was essential for protecting water from being evaporated by solar radiation, thus allowing life to evolve. Tarduno told Stephanie Pappas of Live Science:
“We need the Earth’s magnetic field to preserve water on the planet. But it is sort of an interesting twist that during the Ediacaran, the really weak magnetic field may have helped accelerate evolution.”
Of course, the new findings don’t disprove the plant idea we discussed earlier, and they aren’t claiming that to be the case. Instead, they believe their research shows that Earth accumulated oxygen during the Ediacaran in multiple ways. Tarduno explained to Hunt that:
“We do not challenge that one or more of these processes was happening concurrently. But the weak field may have allowed oxygenation to cross a threshold, aiding animal radiation (evolution).”
So it seems the increasingly complex evolution of the first plants and animals probably wasn’t solely responsible for the surplus of oxygen in Earth’s oceans and atmosphere but was aided by the weakened magnetic field.
Perspective Shift
I find it unsurprising that multiple factors likely influenced oxygen levels on Earth almost 600 million years ago — or at any point, really. After all, Nature very rarely utilizes only one tool to accomplish anything. This research helps show that it wasn’t just one thing that led to complex life evolving, but likely a multitude of factors that worked together.
Our species habitually finds an answer to a question and then calls it good. We stop looking for more information or asking whether there’s more to the answer than we found. But research shows us the error of our ways while providing a clearer picture of the past and how Nature works.
You’re currently reading my free newsletter, Curious Adventure. If you want more, you’ll likely enjoy my other newsletter, Curious Life, which you’ve already received sneak peeks of on Monday mornings. The subscription helps me pay my bills so I can continue doing what I love — following my curiosities and sharing what I learn with you.
Also, if you enjoy my work and want to show me support, you can donate to my PalPal. Thank you for reading. I appreciate you.
I absolutely love this stuff.
Interesting. A good reminder that major planetary systems will change again and again in the future.