When the Earth’s temperature rose and the amount of oxygen in the oceans decreased about 252 million years ago, most life on our planet suffered the same tragic fate. It is estimated that this extinction event, also known as the “Great Dying”, killed 70% of species on land and about 96% of species in the oceans. Illustration: Getty However, there are no sharks among them. “They’re the last surviving species,” said Elizabeth Sibert, a paleontologist and identifier of fossils and an oceanographer at Yale University. The next extinction event at the end of the Triassic period or even the meteorite event that wiped out the dinosaurs 66 million years ago could not have caused the shark to become extinct. The shark’s survival or longevity is extraordinary, but the animal was also close to the brink of extinction, a study in the journal Science revealed June 3. The study, led by scientist Sibert, shows that a previously unknown extinction event pushed sharks to the brink of extinction 19 million years ago, leaving just one in ten of the sharks. Sharks in the oceans survive. “Something happened and wiped out 90% of the shark population overnight,” said scientist Sibert. The so-called something is still uncertain but it has caused immense destruction. The meteorite that wiped out the dinosaurs on Earth only caused 30-35% of the shark species to be wiped out while the above event was 2-3 times worse. To find this discovery, oceanographer Sibert and his collaborator Leah Rubin went through a remarkable process. Discover the mystery When a marine species dies, its body will fall to the bottom of the sea and decompose into discrete parts. Small parts, such as their teeth, will gradually accumulate in the sediments under the sea. “The seabed is essentially a grave for all aquatic species,” Sibert said. The sediment samples used in this study were collected from two locations in the Pacific Ocean, one in the north and one in the south, covering a period of 40 million years. However, it was not easy to analyze the small teeth inside each of these specimens. These parts are so small, even smaller than the width of a human hair. Oceanographer Sibert filtered dried sediment samples under a microscope and isolated the tiny bits of shark teeth. After separating them, scientist Rubin will identify and describe the features, as well as classify them. These little bits of teeth can reveal a lot to us. There were about 1,300 small tooth pieces identified in the above study with 85 samples with different shapes. Most of them are from the period before 19 million years and only a few samples belong to the later period. So, the question arises, what happened to the sharks? The tip of the iceberg The small tooth fragments suggest a decline in shark numbers and diversity about 19 million years ago, but the cause behind this event is unknown. “This is really a mystery. Right now we don’t know what happened,” Ms. Sibert said. The key to solving this mystery is to learn about the time when the sharks almost disappeared. This period is called the “Miocene” and is described by the scientist Sibert as the “transition phase” of the Earth. 15 million years before the mysterious shark event occurred, the Earth gradually became an “ice house” as permafrost increased in Antarctica. The oceans at that time were no different from the oceans of today, although we cannot find such species as tuna, swordfish and seabirds. Dolphins and whales had not yet evolved. However, there is not much evidence to find out the cause of the shark eradication. Even the discovery, which took place during a rather unusual time in Earth’s history, is just the tip of the iceberg. “There are many questions that need to be answered,” said researcher Rubin. Did some change in the environment lead to the decline in shark populations? This is difficult to confirm because the oxygen and carbon levels show no anomalies, but scientists can use more data around this time stamp. Did the event happen across the oceans and affect other marine species as well? Ms. Sibert said this is a global event but we still need more data. Also, what about other bodies of water? Can sedimentation in lakes and coastal areas occur other phenomena? How were terrestrial species affected during this time? Are there any chemicals that can tell us about the environment then? Ms. Sibert even thought that an epidemic, such as a virus, could be responsible for the decline in shark populations. Still, for this oceanographer, the extinction event was a remarkable phenomenon. The fact that sharks have existed for more than 400 million years, surviving multiple extinction events leads her to believe that something truly intense happened and that the sharks may be the gateway to understanding major changes. collided with Earth during the early Miocene. “There is a lot of data waiting to be discovered,” said researcher Rubin. The discovery not only shows the unpredictable change of the marine environment, but also shows how difficult it is for species to recover when they are pushed to the brink of extinction. “Biology is trying to tell us something and I think we need to listen,” Sibert said.

Tiny bacteria on Earth have bitten these plant remains with specialized enzymes. But because the hungry microorganisms process a large amount of carbon in the soil, even taking in some elements into their cells, the bacteria cannot do the full job, so there are pieces of carbon that are not broken down. dishwashing bacteria. Moreover, they also have carbon in their bodies, so when the bacteria die, the carbon goes back to the ground. It’s a cycle, where there’s always carbon left over. These small pieces accumulate over time. Illustration. Such tiny pieces are the humus material, which accumulates year after year. And bacteria’s carbon storage has given the earth its dirty brown color, because carbon absorbs most of the colors in the solar spectrum, except for the brown light it reflects back. However, not all land on earth is brown. Some deserts seem to have only white sand. The soil in Hawaii, rich in iron, is reddish in color. Dig deep into the ground in some areas that are dirty brown, you’ll see other colors underneath. If there wasn’t too much carbon in the ground, the ground would be yellow, red, and gray. They depend on the color of the dominant mineral there. The Mysteries of the Earth 1. Does anyone know what the structure of the middle layer of the Earth is? According to research by seismologists, we already know that the internal structure of the Earth includes: The inner core is solid. The outer core layer is molten lava. The intermediate layer, called the mantle or mantle, lies at a depth of 30 to 2,900 km. The rock crust can slide away freely. But what the mantle is made of is still a mystery to researchers because we haven’t been able to dig down to this layer or have any evidence of its composition. Until now, the deepest hole that humans can dig is the Kola Drilling Hole in Russia, only 12.3 km deep. 2. Earth’s two poles are interchangeable Scientists have proven that the two magnetic poles of the Earth can change positions and reverse directions. This phenomenon has happened many times in Earth’s history. The last time the Earth changed polarity was 10 million years ago, and it is likely that this will happen again in the future. Until now, scientists did not know how this phenomenon could happen. 3. Earth used to have two moons Scientists confirm that, 4.6 million years ago, Earth had two natural satellites. The second satellite exists in the same orbit as the Moon and has a diameter of about 1,200 km. After a few million years, these two satellites collided. This may explain why the two halves of the Moon are so different today. 4. The Earth actually rotates very fast The Earth, including the atmosphere and everything on the planet’s surface, rotates at a tremendous speed of more than 1,600 km/h, while the Earth’s rotation speed around the Sun is 108,000 km/h. Humans can live and function normally while standing on the ground because we, everything around and the Earth are rotating at the same speed. We can feel this movement thanks to the wind, but since the entire atmosphere is moving at the same speed as us, we don’t feel anything. If the Earth suddenly stopped rotating, we could feel this movement. But it will not be pleasant at all, everything on Earth will be swept away at more than 1,600km/h. 5. Time on Earth is “getting longer” every day 620 million years ago, a day on Earth lasted only about 21.9 hours. But the Earth is spinning more and more slowly, so in the future, our day will be 25 hours long. Scientists have shown that after every century, the Earth’s rotation slows down by about 1.8 milliseconds, which means that a day will be only 2 milliseconds longer. So we have to wait another 200 million years for a day on Earth to have 25 hours. 6. Gravity on Earth is not the same everywhere The Earth is not a perfect sphere, so Earth’s gravity is not uniform, there will be areas of weak gravity and regions of different strong gravity, even places where there is almost no gravity. Hudson Bay in Canada is known as a place of near zero gravity due to the low density of rock here, caused by the rapid melting of glaciers. 7. In primitive times, the Earth used to be purple In ancient times, plants used retinal instead of chlorophyll to absorb light. This substance causes them to reflect red and blue light. This is the reason why ancient plants were red, not green like today’s plants. This led scientists to hypothesize that the original Earth was once purple because it was covered with ancient plants. 8. The ocean hidden in the ground Scientists believe that there is a giant ocean, and the amount of water contained in it is estimated to be three times greater than that of all the oceans on the Earth’s surface. In early 2014, researchers discovered “ringwoodite,” a material located in the transition zone (between 410 km and 660 km deep), as proof that a giant sea of ​​water exists. exist below the surface of the Earth. According to scientists, this underground ocean is about 2.7 million years old, under tremendous pressure.

As plants wilt and die, their leaves and branches fall, carrying the carbon they’ve stored into the ground. Tiny bacteria on Earth have bitten these plant remains with specialized enzymes. But because the hungry microorganisms process a large amount of carbon in the soil, even taking in some elements into their cells, the bacteria cannot do the full job, so there are pieces of carbon that are not broken down. dishwashing bacteria. Moreover, they also have carbon in their bodies, so when the bacteria die, the carbon goes back to the ground. It’s a cycle, where there’s always carbon left over. These small pieces accumulate over time. Such tiny pieces are the humus material, which accumulates year after year. And bacteria’s carbon storage has given the earth its dirty brown color, because carbon absorbs most of the colors in the solar spectrum, except for the brown light it reflects back. However, not all land around the earth is brown. Some deserts seem to have only white sand. The soil in Hawaii, rich in iron, is reddish in color. Dig deep into the ground in some areas that are dirty brown, you’ll see other colors underneath. If there wasn’t too much carbon in the ground, the ground would be yellow, red, and gray. They depend on the color of the dominant mineral there. The Mysteries of the Earth 1. Does anyone know what the structure of the middle layer of the Earth is? According to research by seismologists, we already know that the internal structure of the Earth includes: The inner core is solid. The outer core layer is molten lava. The intermediate layer, called the mantle or mantle, lies at a depth of 30 to 2,900 km. The rock crust can slide away freely. But what the mantle is made of is still a mystery to researchers because we haven’t been able to dig down to this layer or have any evidence of its composition. Until now, the deepest hole that humans can dig is the Kola Drilling Hole in Russia, only 12.3 km deep. 2. Earth’s two poles are interchangeable Scientists have proven that the two magnetic poles of the Earth can change positions and reverse directions. This phenomenon has happened many times in Earth’s history. The last time the Earth changed poles was 10 million years ago, and it is very likely that this will happen again in the future. Until now, scientists did not know how this phenomenon could happen. 3. Earth used to have two moons Scientists confirm that, 4.6 million years ago, Earth had two natural satellites. The second satellite exists in the same orbit as the Moon and has a diameter of about 1,200 km. After a few million years, these two satellites collided. This may explain why the two halves of the Moon are so different today. 4. The Earth actually rotates very fast The Earth, including the atmosphere and everything on the planet’s surface, rotates at a tremendous speed of more than 1,600 km/h, while the Earth’s rotation speed around the Sun is 108,000 km/h. Humans can live and function normally while standing on the ground because we, everything around and the Earth are rotating at the same speed. We can feel this movement thanks to the wind, but since the entire atmosphere is moving at the same speed as us, we don’t feel anything. If the Earth suddenly stopped rotating, we could feel this movement. But it will not be pleasant at all, everything on Earth will be swept away at more than 1,600km/h. 5. Time on Earth is “getting longer” every day 620 million years ago, a day on Earth lasted only about 21.9 hours. But the Earth is spinning more and more slowly, so in the future, our day will be 25 hours long. Scientists have shown that after every century, the Earth’s rotation slows down by about 1.8 milliseconds, which means that a day will be only 2 milliseconds longer. So we have to wait another 200 million years for a day on Earth to have 25 hours. 6. Gravity on Earth is not the same everywhere The Earth is not a perfect sphere, so Earth’s gravity is not uniform, there will be areas of weak gravity and regions of different strong gravity, even places where there is almost no gravity. Hudson Bay in Canada is known as a place of near zero gravity due to the low density of rock here, caused by the rapid melting of glaciers. 7. In primitive times, the Earth used to be purple In ancient times, plants used retinal instead of chlorophyll to absorb light. This substance causes them to reflect red and blue light. This is the reason why ancient plants were red, not green like today’s plants. This led scientists to hypothesize that the original Earth was once purple because it was covered with ancient plants. 8. The ocean hidden in the ground Scientists believe there is a giant ocean, and the amount of water contained in it is estimated to be three times greater than that of all the oceans on the Earth’s surface. In early 2014, researchers discovered “ringwoodite,” a material located in the transition zone (between 410 km and 660 km deep), as proof that a giant sea of ​​water exists. exist below the surface of the Earth. According to scientists, this underground ocean is about 2.7 million years old, under tremendous pressure.