Extinctions
18 important questions on Extinctions
What is the Ordovician-Silurian event?
- The extinction wipedout more than 100 families of marine life
- Cause: Suddenly from greenhouse to icehouse. Glaciation -> altered ocean temperatures -> lowering sea level -> changes shore habitats
What is the End-Devonian event?
- Extinctions of marine organisms, corals and other marine invertebrates
- Cause: Removal of CO2 from the atmosphere after emergence of land plants -> cooling of the planet
Permian Triassic / End permian extinction
- First to hit land species, more than half of all plants were lost
- Cause: Massive volcanism, methane release
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What are the direct / indirect causes of extinction?
Indirect: Volcanic eruptions or asteroid impacts
What happens with Asteroid and volcanic eruptions?
To which species are asteroid and volcanic events fatal?
The drop in sea level can devastate shelf habitats
What happens when the sunlight is blocked?
- Cascade food chain
What is "Snowball Earth"
- Only single-celled organisms lived then
- After the snowball period, temperatures rose and multicelled organisms evoled
What are the oxygen isotopes? And what do they say?
- The ratio indicates past sea surface temperature
- Ocean water high in 18O -> Cooler climates
- Lower 18O/16O ratios indicate warmer, non-glacial periods
What is the Paleocene-Eocene thermal maximum (PETM)?
- Loss of foraminiferan species, sudden appearance of land groups
- It may have been caused by volcanism or released of methane from the sea
- Major warming -> less oxygen in the ocean -> marine animals died
What is the onset of major land glaciation in Antarctica?
- In cool glacial periods the hydrates are stable, so no methane is released
What happen with the onset of the ice ages?
What happend in the Pleistocene?
- Forests disappeared
- Tundra expanded
What happened in the End-Pleistocene beginning Holocene?
- These coincided with rapid warming and humand arrival
What do missing extinctions illustrate?
Why was it important that the length of the warm periods were short?
When do marine extinctions occur?
Which species are affected the most by the major and minor extinction events?
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