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Modern scientists have made incredible strides in understanding Earth's ancient past, uncovering surprising revelations that challenge our previous assumptions. Revelations such as...
10. Mammals Were the Dominant Life Forms on Earth Long Before Dinosaurs Appeared
Mammals and reptiles may look different, but they share a common ancestor. As they diverged, reptiles, including the forebears of dinosaurs, evolved into diapsids, while the ancestors of today's mammals evolved into synapsids. This rivalry lasted for over 230 million years, with mammals (synapsids) completely dominating the diapsids (dinosaurs) for the first part of that era.
Dimetrodon, a sail-backed mammalian ancestor, was the dominant land carnivore during the Permian period. Measuring meters (11.5 ft) long and weighing 100–150 kilograms (220–330 lb), it had a massive head and long fangs. The sight of it emerging from the swamp waters was the last thing many creatures—including other dimetrodons—ever saw.
The Permian period was harsh on diapsids. They left few fossils behind, but we know some grew as large as 2 meters (6 ft), though most remained small and evaded the dominant synapsids. Then came the “Great Dying,” where over 90 percent of all species went extinct by the end of the Permian.
Synapsids found a strong ecological niche, and some survived the extinction event. These survivors became more widespread, but by then, the diapsids had begun to thrive again. The mass die-off had created opportunities for the dino-diapsids to flourish. Over millions of years, the conflict continued, with synapsids evolving into modern mammals, while diapsids were evolving into dinosaurs. They weren't massive yet, but they were becoming large.
The first dinosaurs were no bigger than a typical modern dog, but by the end of the Triassic period, some had grown to 6 meters (20 ft) in length. One group—ichthyosaurs—had already claimed dominance in the seas. Another mass extinction event followed, and dinosaurs inherited the land. This event sealed the end of the synapsid era, leaving only small modern mammals to carry on.
9. The True Cause of the Dinosaurs' Extinction Remains a Mystery
The end-Cretaceous extinction, according to the most accepted theory from the 1980s to today, unfolded something like this: Dinosaurs once dominated Earth. Then, a massive asteroid struck near present-day Chicxulub, Mexico, triggering a global winter. This event led to the extinction of dinosaurs, with 80 percent of Earth's species vanishing. Mammals then rose to prominence. Since undeniable evidence pointed to an impact occurring in the right place at the right time, scientists have largely embraced this explanation. Some even speculated that impacts might have been responsible for all of Earth's mass extinctions.
Expeditions began in search of more craters. They found many, but most couldn’t be directly linked to a mass extinction. As new questions arose regarding the end-Cretaceous extinction and the asteroid impact, it became clear that such a powerful event should have wiped out life across the globe. Yet, some species managed to survive—even dinosaurs, which later evolved into birds.
Some experts propose that the Chicxulub impact, coupled with massive volcanic activity from the Deccan traps, was the cause of the extinction. According to this theory, the volcanic eruptions made life on Earth extremely difficult, and the asteroid impact delivered the final blow to the most vulnerable species, including T. rex and its contemporaries.
It’s a compelling theory, but not everyone agrees. Other researchers claim to have found evidence suggesting dinosaurs thrived alongside the Deccan volcano during its eruptions, even nesting on its lava. These experts argue that, toward the end of the dinosaur era, Earth was struck by multiple large impacts—asteroids or fragments of comets—within a brief period. While Chicxulub was one of them, the largest impact came from Shiva, which was three times the size of Chicxulub. When Shiva collided with Earth off the western coast of modern-day India, its impact was so immense it altered plate tectonics in the region. The nearby Deccan eruption then intensified, leading to a mass extinction.
So, what’s your theory? Was it Chicxulub, the combination of Chicxulub and volcanic activity, or the Shiva impact plus volcanism that ended the age of dinosaurs? No one knows for sure.
8. It’s Possible for Diamonds to Rain Down
However, you wouldn’t want to be around to catch them. This phenomenon occurs during violent volcanic eruptions.
Diamonds are pure carbon crystals formed under extreme heat and pressure deep within Earth’s interior. The process of how carbon reaches such depths remains unclear, but one thing is certain—diamonds are very, very old.
Once created, diamonds stay in the mantle, undisturbed. Plate tectonics may cause a continent to pass over them, scraping up a few along the way. Over millions of years, the oldest parts of continents gather diamonds like ship keels collecting barnacles.
Unfortunately, none of this leads to wealth. Diamonds can’t naturally exist on Earth’s surface—if they do, they turn into graphite. The only way we have any is through deeply rooted volcanic eruptions that bring them up so quickly that they don’t have time to change.
Here’s how this happens: A rare type of molten mantle rock called kimberlite or lamproite rises rapidly from beneath the diamond-filled mantle. This occurs quickly because the magma is “fizzy,” filled with carbon dioxide and water. As the kimberlite rushes upward, it collects diamonds along the way, breaks through the continent above in a diamond pipe, and boom—it’s raining diamonds.
7. Oceans That Are Purple
Ocean water is mostly clear, but its color varies based on its contents—muddy brown or yellow near coastal areas where rivers empty into the sea, or a grayish-green further out, influenced by seaweed and countless tiny organisms.
However, we're mostly familiar with the upper layers of the ocean, which sunlight can penetrate. Here, plankton use light to photosynthesize, and just like on land, one of the byproducts is oxygen. This oxygen spreads throughout the ocean, even reaching the cold, dark depths, because it dissolves well in cold water and is carried by seafloor currents.
In certain areas, such as some of Norway’s fjords, seawater becomes stagnant. Excess nutrients accumulate, depleting the oxygen. As a result, the local food chain shifts from oxygen to nitrogen, and once that’s used up, to sulfur. This sulfur-based food chain produces hydrogen sulfide, which is harmful to most marine life but supports the green and purple sulfur eaters. These bacteria, which thrive in sulfur, give the water a pink to purple hue and can be found in the Black Sea and a few other fjords and lakes.
Where did they originate from? These sulfur-eating bacteria are some of Earth's oldest residents.
Pigments from tiny purple sulfur-eating bacteria have been discovered in 1.64-billion-year-old rock from what is now northern Australia. These bacteria were thriving just after Earth stopped producing its banded iron formations (BIFs), which ceased forming in the ocean around two billion years ago. Geologists have long been puzzled as to why BIFs stopped forming after that time. Two main theories propose either an oxygen-rich ocean or a foul hydrogen sulfide environment.
The discovery of these pigments provides evidence for the hydrogen sulfide theory. It suggests that the ancient sulfur-rich ocean was teeming with sulfur-eating microbes, giving the waters a vibrant purple hue.
But where did all that water originate from in the first place?
6. A Significant Portion of Earth’s Water Predates the Solar System
The solar system emerged from a vast cloud of interstellar dust. Dust itself is dry, but some of the hydrogen and oxygen in the cloud could have combined to form H2O. However, once the Sun ignited, this water would have been pushed out of the inner solar system. After that, the only places where water could have remained were in the outer solar system or at the edges where comets orbit.
Scientists have studied this and concluded that Earth’s oceans likely formed about one billion years after the planet itself came into being. This process probably involved a mix of volcanic outgassing and impacts from icy comets. Volcanoes would have released any water that was trapped inside Earth during its formation, while comets bombarded the planet, bringing additional water during the early years of the solar system.
It’s a compelling theory and has stood the test of time. But it’s likely only part of the whole picture.
Recent discoveries show that 30-50 percent of Earth’s water is older than the solar system itself. This means interstellar ice was already here before the cloud that created our solar system. By using a relative dating method, scientists have determined that up to half of the water, including the one in your body, is over 4.6 billion years old. While they can’t pinpoint an exact age, this ancient water could be nearly as old as the universe itself.
5. Life Might Have Come To Earth From Mars
Meteors streak across the night sky or even catch us off guard in the middle of the day. These small pieces of asteroid or comet debris typically burn up in the atmosphere. If any survive the journey and reach the surface, they’re known as meteorites.
In the 1980s, following the Viking missions to Mars, scientists were astonished to find that some meteorites seemed to have come from Mars. Today, NASA is fairly confident that they have at least 124 pieces of Martian rock in their collection. These Mars meteorites appear to be volcanic in nature, and Mars is home to the largest volcanoes in the solar system. Yet, even the colossal eruptions at Olympus Mons couldn't have sent these rocks to Earth.
After much investigation, some experts believe that an impact launched these 4.5-billion-year-old volcanic rocks into space roughly 15 million years ago. These rocks then landed on Earth around 13,000 years ago. Some of these meteorites even contain fossil-like features or evidence suggesting that the rock formed in water that could have supported life.
This idea may seem improbable, since these rocks were once lava, but life is resilient. Today, extremophiles—tiny organisms—thrive in Yellowstone’s hot springs and in the surrounding rocks. These hardy creatures, capable of surviving in supervolcanoes, could potentially withstand Mars’ extreme conditions. If they were embedded deep enough inside a large rock slab, they might even survive an impact. As for the fiery descent to Earth, experiments have shown that endoliths would likely only require a mere 5 centimeters (2 inches) of rock to act as a heat shield.
Of course, life on Earth is around four billion years old, and these Martian visitors are relatively recent arrivals. However, we haven't discovered all the meteorites yet. These particular ones definitely made it here, so others from Mars may have reached Earth when it was still quite young. Even if they didn’t deliver life itself, Martian meteorites might have brought along the minerals necessary to spark life on Earth.
4. Early Earth Wasn’t Hellish
Geologists refer to Earth’s earliest years as the Hadean period, named after Hades, who in Greek mythology is often associated with Hell. The intense heat from Earth’s formation, according to theory, melted much of the planet, which then took a long time to cool and form the surface crust we recognize today. Most of the material from the Hadean period has been lost due to weathering and plate tectonics. All that remains are tiny crystals of zircon.
Zircon (zirconium silicate) is known for making beautiful jewelry, but it also serves scientists well for two important reasons. First, it’s incredibly durable, capable of surviving geological processes such as volcanic eruptions, tectonic plate collisions, and being buried under miles of sediment. Zircon simply grows a new layer in response. Scientists can later read these layers like a historical record. Second, zircon contains a small amount of uranium—enough to allow for precise scientific dating, but not enough to pose a danger.
Researchers examined the oldest known zircon, dating back to the Hadean period. This mineral crystallized at a temperature far cooler than anticipated. Isotope analysis revealed that water and other conditions conducive to life might have existed when the crystal formed. Four-point-four billion years ago, Earth could have had continents and oceans made of life-sustaining water, not the deadly molten lava typically imagined.
However, Earth does have a core that’s composed of iron. This suggests that, for at least a brief period after its formation, the planet must have experienced hellish conditions. It also explains why precious metals come at such a high price—along with your zircon gem, you might just need to pay a little extra for them.
3. Earth May Have Cooled Because Of Ants
Regardless of the recent warming at the poles, Earth’s hottest temperatures over the past 200 million years were recorded during the age of dinosaurs. Back then, the tropics baked at 35 degrees Celsius (95°F) due to the greenhouse effect, while the high latitudes were comfortably in the mid-20s (high 70s °F). But around 65 million years ago, temperatures began to cool, with occasional spikes here and there.
Weathering plays a significant role in the global carbon cycle, which is why this process is often cited to explain the overall cooling trend of Earth since the age of dinosaurs. In the late 1980s, a researcher from Arizona State University began a long-term experiment. He crushed rocks and placed them in various environments—from bare soil to ant nests. Every five years, he would check the amount of weathering in comparison to baseline samples. After 25 years, he was astounded to find that ants were weathering the rocks up to 175 times faster than the baseline rate.
Ordinary ants are among the strongest natural agents of mineral weathering. It’s no coincidence that ants first appeared around 65 million years ago, roughly coinciding with the time Earth began to cool.
While ant-driven weathering may or may not have sequestered enough carbon to significantly affect the planet's cooling, any Earth scientist would likely appreciate receiving an ant farm as a holiday or birthday present. It’s a fun way to introduce them to the latest trends in climate research.
2. The North And South Poles Need Not Be Icy
Possibly due to the Moon-forming impact, Earth’s axis is tilted just enough that most of the sunlight hits the equator. However, this doesn’t mean the poles are always icy. Just about 34 million years ago, a brief moment in geological time, Antarctica’s average temperature was 14 degrees Celsius (57 °F), and the surrounding seas were a comfortable 22 degrees Celsius (72 °F).
For much of its history, Earth hasn’t been home to the massive polar ice caps that we see today. The amount of incoming sunlight doesn’t play the primary role. Instead, the key factor is the concentration of carbon dioxide and the resulting global warming effects.
Scientists aren’t exactly sure why the poles entered an ice age about 20 million years ago. Some believe it occurred after India and Asia collided as part of the plate tectonics process. This collision uplifted Tibet and the Himalayas. The steep terrain accelerated weathering, causing more continental rock to wash into the oceans and increasing the carbon storage capacity of the seas. As carbon was pulled from the atmosphere, the greenhouse effect shifted to cooling the planet.
Not all scientists agree with this hypothesis. Some argue there isn’t enough evidence to favor one theory over another, though they all agree it had something to do with CO2. One suggestion is that changes in vegetation might have played a role.
1. Gold And Platinum Fell To Earth’s Core
Metals like gold and platinum may be rare on Earth today, but they're abundant in some asteroids. These asteroids, just like Earth, formed from the same cloud of cosmic dust. So why don’t we see large amounts of gold and platinum on Earth now?
In the early Hadean, when Earth had just formed but before that zircon crystal we discussed, the planet was hot enough to melt iron. Iron and its neighboring elements on the periodic table are heavy, so molten iron and its mixtures with gold, platinum, and others gradually settled, moving toward the planet's center.
Then, an object roughly the size of Mars smashed into Earth, knocking off debris that would later form the Moon. This colossal impact caused widespread melting on Earth, sending much of the iron and nearly all of its metal companions deep into the core, where they remain to this day.
