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)
2
Q
five mass extinction events
A
- late ordovician
- late devonian
- permo/triassic (big one)
- end triassic
- end cretaceous
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
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
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
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
7
Q
coldhouse earth
A
- ice sheets present at both poles
- lower atmospheric CO2
- currently in coldhouse
8
Q
greenhouse earth
A
- no glaciers anywhere
- higher atmospheric CO2
- most of earths history has been greenhouse
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
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:
- continental configuration
- pangea supercontinent = drop in diversity
- less ecological niches leads to less diversity
- vast deserts on pangea and less shallow seas - ocean stagnation
- anoxia (lack of o2)
- polar waters unable to sink = no ocean circulation - sea level fall
- related to less volcanic activity
- less shallow seas - possible impacts from extra-terrestrial bodies
- helium and argon isotopes founds in sediments - 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
11
Q
dinosaurs
A
evolved during the triassic period due to the ecological space cleared from extinction
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)
- gradual climate change
- increasingly arid, more seasonality
- stress on biosphere - 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 - volcanic eruptions
- flood basalts of the central atlantic magmatic province (CAMP) 200 Ma ~3x106 km3 basalt
- beginning of the end for pangea
