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In the long history of our planet, there have been countless species of creatures on our planet that have flourished for several periods, but each era has finally fallen silent, and each time it seems to be a reset of nature.
From the disappearance of dinosaurs to the birth of countless species, these events have shaped biodiversity as we know it today. But when we look back at the past, we can't help but ask:Are we standing on the threshold of the sixth mass extinction?
Ordovician, an ancient era in the long history of the earthStarted at 48.5 billion years ago, ending at 44.3 billion years ago. The land looked very different at this time than it is today.
At that time, the vast shallow sea covered a large area of land, and the concentration of greenhouse gases, like carbon dioxide, was much higher than it is now, and the world was in a state of constant high temperatures. In this environment, marine life can be said to have ushered in their "** era".
In the Ordovician oceans, invertebrates were the overlords. Trilobites, brachiopods, corals, sea lilies, bryozoans, and many moreThere are so many types that I can't count them, and the number is even more amazing.
They either float on the surface of the water or live on the bottom of the sea, and the entire ecosystem is made up of them, which is colorful and intricate.
On land, although life seems a little "weak" here, green algae and the earliest nonvascular plants have begun to bravely explore this new world.
Unfortunately, the good times were short-lived. Towards the end of the Ordovician period, a cataclysm struck the earth. Scientists generally agree that this period ushered in a massive ice age, with sea temperatures plummeting by about 5 degrees, leading to a massive decline in life.
To make matters worse, there may have been a huge celestial body that hit the Earth, with devastating consequences. A huge cloud of dust enveloped the Earth, leading to the Great Ice Age of the Early Paleozoic Era, where many invertebrates were unable to adapt to this environmental change and became extinct.
What's even more shocking is that some experts believe thatA gamma-ray burst released by a supernova could be the culprit. Although it only bombarded the earth for about ten seconds, the huge energy directly destroyed half of the ozone layer, causing the death of a large number of organisms, and about 85% of all species were destroyed.
Devonian,It started around 4The era of 1.6 billion years ago, a period of prosperity for life on earth. This stage is called the "** years of life"., witnessing many creatures shine.
On land, gymnosperms and ferns are beginning to carve out new territories, their roots digging deep into the soil, altering the weathering of the surface and the elemental cycle. In the oceans, brachiopods and corals prevailed, primitive ammonites and insects appeared, and primitive amphibians and labyrinthine teeth began to emerge in the late stages.
Unfortunately, this boom did not last long. End of the Devonian,Approximately in 35.9 billion years ago, the Earth experienced a massive extinction event.
This extinction event has been broken down by scientists into several minor events, the most serious of which are the Kelvase event and the Hangenburg event. These events resulted in the disappearance of about 19% of families and 50% of genera.
So, what exactly caused this catastrophe? Scientists have come up with a variety of hypotheses. Some include drop temperatures, changes in geography due to undersea volcanic eruptions, and drops in oxygen levels.
There are even more surprising theories, such as that energy from the universe has destroyed the Earth's atmosphere, which increases ultraviolet radiation on the surface of the earth, poses a great threat to living beings.
This period was a period of transition from a cold glacial period to an arid desert climate, and biodiversity and complexity reached unprecedented heights. Sadly, the end of this era ended with an unprecedented mass extinction.
On the Permian stage, the diversity of life was like a shining star. On land, early gymnosperms and seed ferns began to dominate the forests, while in the oceans,Organisms such as brachiopods, ammonites, and corals build complex ecosystems.
However, the end of this period was a tragedy. About 2500 million years ago, life on Earth suffered a catastrophic blow, the famous Permian-Triassic mass extinction event.
Scientists have conducted a multifaceted study of the causes of this mass extinction. Some studies argue thatLarge-scale volcanic activity may have been one of the main causes of this extinction.
Volcanic eruptions in Siberia have released large amounts of greenhouse gases, causing global warming, ocean acidification and hypoxia, with devastating impacts on biodiversity.
In addition to this, there are studies that point outA combination of factors such as changes in sea level, the release of methane hydrates, and the arid climate brought about by the formation of Pangea may have played a role in this extinction event.
In about 25.1 billion years ago was the beginning of the Mesozoic Era, named after a unique sequence of three layers of rock discovered by German geologists. Compared to our planet today, the world of the Triassic was completely different.
It was a time when the whole world was a huge land connected together, and it was a time when there were no glaciers and the climate was warm and dry.
This period has witnessed a great transformation of life. The mass extinction at the end of the Permian caused the disappearance of many biological species, providing space for the emergence of new species.
On land, dinosaurs and pterosaurs have not yet become dominant, but other reptiles such as master dinosaurs and pseudocrocodiles dominate the top of the ecosystem.
In the ocean, new corals and cephalopods began to appear, marking a new chapter in Mesozoic marine life. However, the end of this era was likewise accompanied by disaster.
About 20.1 billion years ago, at the end of the Triassic period, the Earth experienced another mass extinction event that affected biodiversity in the oceans and on land.
Scientists have come up with a variety of theories to explain the extinction, including climate change, sea level changes, impact events, and massive volcanic eruptions.
Among them, volcanic activity in the Mid-Atlantic Magma Province is considered to be one of the main causesIt could have led to drastic changes in the global climate, which affected the ecosystems of the time.
In distant history,The earth once went through an era known as the Cretaceous period. It was a time of great life, with dinosaurs dominating the land, huge sea creatures swimming underwater, and lush vegetation spreading all over the land.
The Cretaceous climate was warm and humid, greenhouse gases peaked, the temperature on Earth was relatively balanced, and there were no permanent ice sheets in the polar regions.
However, this era of prosperity came to an abrupt end 66 million years ago. A huge extinction event swept the globe, causing the mass disappearance of many species, including dinosaurs.
Scientists generally agree thatThe main cause of this extinction event was the double whammy caused by the impact of an asteroid and a prolonged volcanic eruption.
The energy generated by the impact was like detonating millions of cores**, triggering a global firestorm and tsunami, a large amount of dust and volcanic ash obscured the sunlight, and the earth fell into a "nuclear winter" for a while.
Plants are unable to photosynthesize, the food chain collapses, and many organisms struggle to survive because they can't get enough food.
This extinction event not only ended the domination of the dinosaurs, but also provided an opportunity for the rise of mammals. After the disappearance of the dinosaurs, mammals began to evolve massively and eventually became the dominant land animals on Earth.
The end of the Cretaceous period marked the end of the Mesozoic Era and the beginning of the Cenozoic Era, opening the prelude to a new geological era.
Looking back at mass extinction events in Earth's history does give rise to a deep thought:Are humans at similar risk? Although the question is fraught with uncertainties, scientists have begun to explore what could have led to the extinction of humans.
First of allWe must acknowledge that the impact of human activities on the earth's environment is enormous. Issues such as climate change, pollution and large-scale deforestation have captured global concerns.
With industrialization and population growth, our demand for natural resources is increasing, which not only leads to the destruction of ecosystems, but may also pose a threat to the future of humanity.
SecondlyThe progress of science and technology has brought unprecedented challenges. For example, the presence of nuclear ** gives humans the ability to cause widespread destruction in a very short period of time.
In addition, the development of artificial intelligence and biotechnology, although in many ways has brought convenience to our lives,But it can also carry the risk of not being able to **.
There are also astronomical threats, such as the possibility of an asteroid hitting Earth. Although the probability of such an event is low, if it does, the consequences will be unimaginable.
Some of these potential threats can be mitigated through efforts to reduce risks, such as mitigating climate change by reducing greenhouse gas emissions, or preventing the proliferation of nuclear ** through international cooperation.
But there are some threats, such as asteroid impacts, and we need more scientific research and technological advances to warn and defend against them in advance. Awareness of potential future disasters can motivate us to work together to take effective measures to protect our future.
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