Many things happened in the past that shaped Earth today. Several mass extinction events occurred, giving us a world without dinosaurs and megalodons. There are at least five extinction-level events.
What Is Mass Extinction
Animals and plants exterminate themselves regularly — roughly 98% of them have now gone extinct. Extinction is a part of life, and that's a fact of existence.
A mass extinction event occurs when a species disappears far more quickly than it is replaced. This is typically understood to mean that fewer than 2.8 million years, or around 75% of all species on Earth, have disappeared.
It's challenging to pinpoint the beginning and end of global extinction, according to Dr. Katie Collins, the Natural History Museum's curator of benthic mollusks. However, according to her, we already know five significant occurrences where extinction rates were far greater than the background rate. These events are frequently used to determine if we are in the midst of one.
Extinction Level Event
We know that huge dinos used to walk on the Earth, and megalodons dominated the ocean. Their demise was just among the five global events that wiped millions of species out.
The five extinction-level events are as follows:
1. Ordovician-Silurian Extinction: ~ 440 million years ago
Species made extinct: 85%
At the time of the first mass extinction on Earth, the world's shallow waters were populated by creatures like corals and shelled brachiopods, but they had not yet made it onto land. A little over 3.7 billion years ago, life first appeared, and it was just then that it started to spread and diversify. But 440 million years ago, a climatic change led to a change in water temperature, resulting in the extinction of most marine life.
It is unknown what expressly set off these events. According to one theory, the Appalachian Mountains' creation in North America may have contributed to the cooling process. Carbon dioxide removal from the atmosphere is connected to the extensive weathering of these mountainous silicate rocks.
Another theory claims that harmful metal may have dissolved into ocean waters during an oxygen deprivation period, eradicating marine life. Meanwhile, other scientists believe that a supernova's gamma-ray blast tore a huge hole in the ozone layer, allowing harmful ultraviolet radiation to kill various species. Another study suggested it was due to volcanism.
2. Late Devonian Extinction: ~ 365 million years ago
Species made extinct: 75%
This period saw the emergence and extinction of a number of ancient marine creatures. Most of life was swimming through the waters, even though animals had started to evolve on land. That is, until vascular plants, like trees and flowers, probably brought about a second global extinction.
As plants developed roots, they unintentionally changed the environment in which they resided by changing rock and rubble into soil. The world's oceans then absorbed this nutrient-rich soil, leading to a massive algae bloom. These blooms produced enormous "dead zones," regions where algae deplete the water's oxygen, strangling marine life and upsetting marine food webs. Species that failed to adapt to the food shortage and the decreasing oxygen levels did not survive.
3. Permian-Triassic Extinction: ~ 253 million years ago
Species made extinct: 96% marine life; 70% terrestrial life
This mass extinction, often known as the "Great Dying," is the worst to ever happen on the planet. It destroyed the land-dwelling reptiles, insects, and amphibians, wiping out around 90% of all species on the earth. This violent eruption was the result of a prolonged era of widespread volcanism.
The region of the earth that is now Siberia had massive volcanic eruptions during the end of the Permian epoch. Due to the significant amount of carbon dioxide released into the atmosphere, exacerbating the greenhouse effect, the Earth became warmer. Weather patterns changed as a result, sea levels rose, and acid rain pelted the earth.
Increased carbon dioxide levels in the ocean harm marine life by robbing it of oxygen-rich water, and the water itself dissolves into the atmosphere. Rising sea temperatures also resulted in lower water oxygen levels.
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4. Triassic-Jurassic Extinction: ~ 201 million years ago
Species made extinct: 80%
The Triassic period saw the emergence of new and varied life, including dinosaurs. Sadly, a lot of volcanoes erupted around that time as well. Experts believe that intense volcanic activity occurred in a region of the Earth that is currently covered by the Atlantic Ocean, even if the cause of this fourth mass extinction is still unknown. Similar to the Permian extinction, climatic change and the loss of Earth's life were caused by massive carbon dioxide emissions from volcanoes.
Alternative explanations for this mass extinction contend that releasing trapped methane from permafrost due to rising carbon dioxide levels would have caused similar occurrences.
5. K-Pg Extinction: ~ 66 million years ago
Species made extinct: 75%
The Cretaceous-Paleogene extinction, sometimes known as the day the dinosaurs died, is the most well-known of all the mass extinction events. Geologists refer to the event as the "K-Pg extinction."
An asteroid about 8 miles (13 kilometers) broad crashed into Earth at about 45,000 mph (72,000 km/h), landing in Yucatán, Mexico. The Chicxulub crater, which is 110 miles (180 km) wide and 12 miles (19 km) deep, was created as a result. The 180 million-year period when the dinosaurs reigned the planet ended as the impact would have burnt all the nearby terrain within 900 miles (1,450 km).
After the asteroid crash, there were months of cloudy skies because of the dust and debris sent into the atmosphere. As a result, plants could not absorb sunlight and went extinct in large numbers, upsetting the food chains that supported the dinosaurs. Additionally, it led to a sharp decline in global temperatures, ushering in a prolonged period of cold weather.
According to experts, we are currently experiencing the sixth mass extinction, which is being driven by human action, primarily (though not exclusively) the unsustainable use of land, water, and energy, as well as climate change, unlike past extinction events that were brought on by natural causes.
Currently, 40% of all land has been used for agricultural purposes. Additionally, agriculture uses 70% of the freshwater globally. It is to blame for 90% of global deforestation, which has a disastrous impact on the animals that live there by drastically changing their ecosystems.
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