Dirt & Sky
Mass Extinctions
What’s happened?
What’s coming?
Rebecca Clotts
1 March 2017
The Geologic Time Scale
4
What is a mass extinction event?
https://www.washingtonpost.com/news/wonk
/wp/2014/02/11/there-have-been-five-massextinctions-in-earths-history-now-were-facinga-sixth/?utm_term=.cfeee88db30b
https://cosmosmagazine.com/palaeontology/big-five-extinctions
Causes of mass extinctions?
http://imgur.com/gallery/1bnvgwn
http://www.bbc.co.uk/nature/extinction_causes
1
2
3
4
5
650 MYA Snowball
2.1
2.4
2.3 BYA
Earth!
The Great Oxygenation Event!
Cyanobacteria produce enough O2
to accumulate in the atmosphere
Rodinia!
http://media.hhmi.org/biointeractive/click/oxygen/
Snowball Earth Evidence
When stromatolites appeared
and began releasing free
oxygen into seawater, the
oxygen immediately reacted
with the iron in seawater and
caused the iron to precipitate
as iron oxide minerals.
100
200
The Cambrian
Explosion
300
400
500
600
542 MYA
Cambrian Explosion
Scotese Plate Tectonics animation (6:34):
https://www.youtube.com/watch?v=g_iEWvtKcuQ
The Burgess Shale Fossil Gallery
: http://www.burgess-shale.rom.on.ca/en/fossil-gallery/index.php
http://www.burgess-shale.rom.on.ca/en/sea-odyssey/index.php
Virtual Sea Odyssey
Cambrian Sea (0:46): https://www.youtube.com/watch?v=XxhecL-1RtI
100
The Ordovician
Extinction
200
300
400
500
600
440 MYA
Ordovician Extinction
Scotese Plate Tectonics animation (6:34):
https://www.youtube.com/watch?v=g_iEWvtK
cuQ
Brachiopods
Lingula is a genus of brachiopods
Graptolites
Trilobites
Trilobite (0:18):
https://www.youtube.com/watch?v=WxK1RWvEKEU
Ordovician Extinction
What dies? Small marine organisms
~2/3 of Brachiopods & Bryozoans
Many families of Trilobites & Graptolites
Ordovician Extinction – Causes?
Ordovician Extinction – or maybe…
A nearby gamma ray burst could have stripped the Earth's atmosphere of
half of its ozone almost immediately, causing surface-dwelling organisms,
including those responsible for planetary photosynthesis, to be exposed
to high levels of ultraviolet radiation.
This would have killed many species and caused a drop in temperatures.
While plausible, there is no unambiguous evidence that such a nearby
gamma ray burst has ever actually occurred.
100
The Devonian Extinction
200
300
400
500
600
365 MYA
Devonian Extinction
Scotese Plate Tectonics animation (6:34) – Start at 1:45:
https://www.youtube.com/watch?v=g_iEWvtKcuQ
Panthalassic Ocean
Warm
High Seas
Reef builders
Start of Pangaea
Preservation of Devonian Reef (Australia)
Ammonites
https://www.youtube.com/watch?v=Ax79qoxbHyE
http://ageoffishes.org.au/
NSW Australian
Devonian Sea (0:46): https://www.youtube.com/watch?v=jWL5xz5B75M
Dunkleosteus: https://www.youtube.com/watch?v=KZJB69v3dmo
Dunkleosteus at the Cleveland Natural History Museum
On the Land…
Devonian Forest (1:16):
https://www.youtube.com/watch?v=KJdCytwAigU
Devonian Extinction
What dies?
Many tropical marine species went extinct (365 mya)
Placoderms
Demise of most Great Reefs
Massive decline of:
Jawless Fishes
Trilobites
Most ammonites
Devonian Extinction – Causes?
Causes of the extinction are debated but may be related to cooling climate from CO2
depletion caused by the first forests. Although up to 70 percent of invertebrate species
died, terrestrial plants and animals were largely unaffected by these extinction events.
Land plants as well as freshwater species, such as our tetrapod ancestors, were
relatively unaffected
100
200
300
400
500
600
The Permian Extinction
The Great Dying
250 MYA
Permian Extinction
Scotese Plate Tectonics animation (6:34) – Start at 2:40:
https://www.youtube.com/watch?v=g_iEWvtKcuQ
What was it like?
Synapsids
Dimetrodon
Lystrosaurs
Permian Extinction
What dies?
96% of Marine species
70% of Terrestrial vertebrates
Trilobites
Corals
Only know mass extinction of insects
The Permian Extinction – Causes?
Impact Calculator: https://www.purdue.edu/impactearth/
The Permian Extinction – Causes?
Volcanic Eruptions?
Siberian Traps: massive eruption
of mostly basaltic lava that
covered 7 million km2.
Other rocks suggest violent
eruptions
The Permian Extinction – Causes?
Ocean acidification?
http://www.nature.com/news/acidic-oceans-linked-to-greatest-extinction-ever-1.17276
http://earthsky.org/earth/ocean-acidification-drove-earths-largest-mass-extinction
The Permian Extinction – Causes?
Microbes?!
Methanosarcina quickly grew in
the oceans. It released
enormous quantities of
methane.
The archaea Methanosarcina seen under a
scanning electron microscope
Methane is a greenhouse gas. It
heated Earth’s temperature and
changed the ocean chemistry
(increased acidity).
http://www.nature.com/news/archaeageddon-how-gas-belching-microbes-could-have-causedmass-extinction-1.14958
https://www.scientificamerican.com/article/methane-spewing-microbe-blamed-in-earths-worstmass-extinction/
100
200
300
400
500
600
The Triassic Extinction
210 MYA
Triassic 210 MYA
Triassic Extinction
Conodonts
Many large amphibians
Triassic Extinction
Many large amphibians
Triassic Extinction
Many Therapsids
Triassic Extinction – Causes?
Climate change and rising sea levels
resulting from the sudden release of
large amounts of carbon dioxide
Plants do not seem largely affected.
100
200
300
400
500
600
The
Cretaceous65 MYA
Tertiary Extinction
Cretaceous-Tertiary Extinction
Impact on Jupiter in 1994 (3:56):
http://www.youtube.com/watch?v=l6AIt36-whc
Walter Alvarez & the K-T Boundary,
Near Gubbio, Italy
Beginning
of Cenozoic,
Tertiary (T)
K-T Boundary
Layer
Rich in Iridium
End of the
Mesozoic,
Cretaceous
(K)
K-T Type location near Gubbio, Italy
48
Cretaceous-Tertiary Extinction – Causes?
Radiolab: Dinopocalypse! (51:12):
https://www.youtube.com/watch?v=ZYoqtBEzuiQ&feature=youtu.be
Start at 21:18 – End at 29:10
http://www.radiolab.org/story/dinopocalypse/
Jay Melosh
http://www.eaps.purd
ue.edu/people/faculty
-pages/melosh.html
49
http://www.icdp-online.org/projects/world/north-and-central-america/chicxulub/
https://www.nytimes.com/2016/11/18/science/chicxulub-crater-dinosaurextinction.html?_r=0
http://www.sciencemag.org/news/2016/11/update-drilling-dinosaur-killingimpact-crater-explains-buried-circular-hills
50
11,000 years ago
100
200
300
400
500
600
The Pleistocene
Extinction?
1.8 MYA to 11,700 years ago
The Pleistocene Extinctions
• ~11,700 years ago, loss of larger mammals in NA,
SA, Australia?, minor loss in Europe, Asia, Africa
• Causes?
• Human hunting
• Climate flux (increased temperature)
• Hyper-disease
54
http://www.pbs.org/wgbh/nova/earth/ice-age-death-trap.html
The Anthropocene
1 Nuclear Weapons –
deposition of radionuclides
2 Fossil Fuels – chemical
signature in trees, glaciers,
limestone, bones/shells
3 Materials – concrete, plastic ,
aluminum
4 Terrain – 50% of land is
altered
5 Soil chemistry – addition of
fertilizers
6 Warmer climate – distinctly
higher than Holocene, higher
seas
7 Mass extinction??
http://images.huffingtonpost.com/2015-01-17-anthropoceneposter.jpg
https://www.theguardian.com/environment/2016/aug/29/declare-anthropocene-epochexperts-urge-geological-congress-human-impact-earth
http://www.smithsonianmag.com/science-nature/what-is-the-anthropocene-and-are-we-in-it57
164801414/
The FUTURE of Plate Tectonics (0:59):
https://www.youtube.com/watch?v=2It3ETk2MGA
Observatory
https://www.youtube.com/watch?v=4P0QtgsD6UU