Term
What biological event spurred the Devonian mass extinction event ?
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Definition
The spread of forests over the continents for the first time in Earth's history.
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Term
Describe the trend of carbon dioxide levels during the Devonian period. How is this trend explained? |
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Definition
After an increase in the first half of the Devonian, CO2 levels plummeted in the second half and into the Carboniferous.
This was largely due to the uptake of CO2 by weathering processes (which was expidited by the new forest ecosystems). |
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Term
| What was the ultimate cause of the Triassic mass extinction? |
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Definition
| Volcanic activity (resulting from tectonic associated with the breakup of Pangea) |
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Term
| What are Siberian Traps and how did they likely contribute to the Permian Mass extinction? |
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Definition
| Basaltic lava flows that covered an enormous area (4 to 7 million hectares). The result of volcanic activity that released large amounts of CO2 into the atmosphere. Additionally, flows caused the burning of large carbon deposits, that released addition greenhouse gases (more CO2 and methane). Forests died out, releasing more CO2. Greenhouse gases contributed to global warming that spurred mass exinction. |
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Term
| In the late Triassic, red cherts are suddenly replaced by grey sediments, and in some locations black sediments. This change in ocean sediments is evidence of what? |
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Definition
| A major drop in Ocean oxygen. |
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Term
| What led to the anoxic ocean conditions seen in the Permian Mass extinction? |
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Definition
| The ocean conveyor stopped (because there was an insufficient temperature gradient between the poles and the equator to propel it). |
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Term
| This was the most devastating of the mass extinction events, killing off between 80 and 85 percent of taxa. |
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Definition
| The Permian Mass Extinction |
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Term
| What could have caused the death of shallow marine species during the Permian mass extinction? |
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Definition
Anoxic Ocean conditions may have caused a build up of Hydrogen Sulfide (produced by anaerobic bacteria) in deep waters that eventually were released all at once, poisoning shallow marine life (and perhaps life on land as well).
A stagnant ocean may have led to the build up of a large amount of CO2 in deep waters that was eventually released all at once, suffocating Oxygen breathing life.
A final explanation is simply that temperature extremes were intolerable. |
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