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Timeline of Evolution

Describes the geologic time scale and the basic timeline of the 4.6 billion-year-old Earth.

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The Great Warming
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The Great Warming

Why It Matters

How Hot is Too Hot?

You've probably heard of mass extinctions. At least the one 65 million years ago which did away with most of the dinosaurs and paved the way for the Age of Mammals. But did you know there was a bigger one?

Even though scientists may have some of the broad strokes figured out as far as the end of the Permian Era goes, there are still lots of unanswered questions. Watch this video and find out about some of the questions scientists from the Smithsonian Institute are working on.

But even when the extinctions were done, the situation didn't improve quickly. It took far longer for ecosystems to recover from the Permian Extinction event (around 5 million years!) than other mass extinctions of which we know (usually 10s of thousands of years), and as you may have guessed, this bugs scientists. But scientists are persistent and new research is providing evidence that global temperatures stayed too hot to be coped with by most plants and animals. Read this article to find out more about this new research. Take particular note of the graphic showing the extent of the "Dead Zone".

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Use the resources below to answer the following questions:

  1. What do scientists think started the Permian extinction 250 million years ago?
  2. What is a mantle plume? How does it differ from other volcanic discharges?
  3. What are the three phases of the Permian extinction event? How do these phases relate to each other?
  4. What is scientists' current explanation for the 12C spike after the marine extinction?
  5. Where was the "Dead Zone" after the Permian Extinction event geographically centered? Why do you think this was? Explain your answer as fully as you can.
  6. If Homo sapiens were around at the time of the Permian Extinction do you think we would have survived? Why or why not? Explain your reasoning as fully as possible.
  7. Recent work has shown that ocean temperatures reached 40°C after the Permian Extinction event. What does this mean to people trying to model climate change? What had they previously assumed?
  8. How are scientists trying to recreate food webs from the Permian Era? What do they hope to learn from this information? What have they found out so far?

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