How many mass extinctions have there been and which one was the most devastating?In the last 500 million years, five great mass extinction events have changed the face of life on Earth. We know what caused some of them, but others remain a mystery.
1️⃣
The Ordovician-Silurian mass extinction occurred
443 million years ago and wiped out approximately
85% of all species. Scientists think it was caused by temperatures plummeting and huge glaciers forming, which caused sea levels to drop dramatically. This was followed by a period of rapid warming. Many small marine species died out.
2️⃣
The Devonian mass extinction event took place
374 million years ago and killed about
three-quarters of the world's species, most of which were marine invertebrates that lived at the bottom of the sea. This was a period of many environmental changes, including global warming and cooling, a rise and fall of sea levels and a reduction in oxygen and carbon dioxide in the atmosphere. We don't know exactly what triggered the extinction event.
3️⃣
The Permian mass extinction, which happened
250 million years ago, was
the largest and most devastating event of the five. The Permian-Triassic extinction event is also known as
the Great Dying. It eradicated
more than 95% of all species, including most of the vertebrates which had begun to evolve by this time. Some scientists think Earth was hit by a large asteroid which filled the air with dust particles that blocked out the Sun and caused acid rain. Others think there was a large volcanic explosion which increased carbon dioxide and made the oceans toxic.
4️⃣
The Triassic mass extinction event occurred
200 million years ago, eliminating about
80% of Earth's species, including many types of
dinosaurs. This was probably caused by colossal geological activity that increased carbon dioxide levels and global temperatures, as well as ocean acidification.
5️⃣
The Cretaceous mass extinction event occurred
66 million years ago, killing
78% of all species, including the remaining non-avian dinosaurs. This was most likely caused by an
asteroid hitting the Earth in what is now Mexico, potentially compounded by ongoing flood volcanism in what is now India.
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