LECTURE 5 Flashcards

1
Q

mass extinction event

A
  • at least 30% of species lost
  • broad range of ecosystems
  • short/sudden duration (~1 ma maximum)
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2
Q

five mass extinction events

A
  1. late ordovician
  2. late devonian
  3. permo/triassic (big one)
  4. end triassic
  5. end cretaceous
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3
Q

is there currently a mass extinction event?

A

not sure if 30% of all species is lost

  • some are still being discovered
  • whilst some are becoming extinct
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4
Q

impact of climate change over the next 10 years

A
  • changing habitats
  • ecosystem loss
  • more extreme weather events
  • rising sea level
  • extinction rate will increase
  • a singular supervolcano has the potential to cause a mass extinction but only through potential climatic effects
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5
Q

causes of mass extinctions

biological causes

A

cause extinction but not mass extinction:

  • competition
  • predation
  • pathogens

biogeology

  • mosses may have caused the late ordovician ice age (and then species extinction)
  • moss dissolves rock
  • rock releases Mg, Ca, Fe
  • these combine with CO2
  • atmospheric CO2 drops
  • temp drops
  • 22x higher CO2 levels in ordovician
  • now only 8x higher
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6
Q

causes of mass extinction

physical causes (earth-based)

A

changes in continental configuration causes changes in:

  • ocean cycles (driven by wind, temp and salinity)
  • climate
  • sea level
  • atmospheric - volcanism
  • greater the landmass, the lower the biodiversity
  • get more biodiversity at the coastline
  • interior deserts if water cannot reach from the coastline
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7
Q

coldhouse earth

A
  • ice sheets present at both poles
  • lower atmospheric CO2
  • currently in coldhouse
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8
Q

greenhouse earth

A
  • no glaciers anywhere
  • higher atmospheric CO2
  • most of earths history has been greenhouse
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9
Q

causes of mass extinctions

extra terrestrial

A
  • impacts
  • supernova - star reaches end of life and explodes - releases lord of radiation and light
  • some think it could have causes the late devonian
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10
Q

permian-triassic (end-permian) extinction (251 Ma)

A
  • permo/triassic extinction - the great dying
  • combination of many factors = worst “day” for biosphere
  • 95-98% of all species became extinct in less than 1 million year duration

potential causes:

  1. continental configuration
    - pangea supercontinent = drop in diversity
    - less ecological niches leads to less diversity
    - vast deserts on pangea and less shallow seas
  2. ocean stagnation
    - anoxia (lack of o2)
    - polar waters unable to sink = no ocean circulation
  3. sea level fall
    - related to less volcanic activity
    - less shallow seas
  4. possible impacts from extra-terrestrial bodies
    - helium and argon isotopes founds in sediments
  5. climate change due to volcanism
    - siberian traps (massive volcanic activity) ~250 Ma
    - 2-3million km3 basaltic lava forms
    - high CO2 in atmosphere
  • greenhouse gases (CO2) were an issue 250 Ma years ago as well
  • CO2 caused greenhouse warming
  • raised global temp by 5c
  • ocean warmed
  • melted clathrates
  • released CH4 (methane)
  • methane = better greenhouse gas than CO2
  • more effective at trapping heat
  • add another 5c in global temp - now 10c warmer
  • clathrates = ice around methane bubbles
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11
Q

dinosaurs

A

evolved during the triassic period due to the ecological space cleared from extinction

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12
Q

triassic-jurassic (end-triassic) extinction (201 Ma)

A
  • 23-34% of marina genera became extinct
  • on land large amphibians and other species became extinct
  • major extinctions of plants
  • 70-75% of all species became extinct
  • class conodonts = index fossils
  • cambrian to end triassic

potential causes (lots of theories)

  1. gradual climate change
    - increasingly arid, more seasonality
    - stress on biosphere
  2. extra-terrestrial impacts
    - several impact craters around the end of triassic
    - eg Rochechouart crater, France (201 Ma) - too small but the correct time
    - eg Manicouagan Reservoir, Quebec (241 Ma) - too early
  3. volcanic eruptions
    - flood basalts of the central atlantic magmatic province (CAMP) 200 Ma ~3x106 km3 basalt
    - beginning of the end for pangea
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