Mass Extinctions
When life on earth had some very, very, very bad days
End-Permian Extinction
Credit Where Credit Is Due
© 2013 The Teaching Company
36 ½-hour lectures
Augmentation from personal library and internet resources
Debate always exists in science
Presenting my take on the current consensus
Astronomers Look “Up, Up and Away”
“What is its composition?” “How did it form?” “What is its physical condition?”
We have visited very few places to make direct measurements
How Do We Know What We Know?
Application of rigorous studies and experiments in the field and in laboratories on earth
Spectroscopy of elements & molecules as a function of temperature & pressure
Dynamics of earth’s landforms - tectonics, volcanism, erosion, sedimentation, etc.
Chemistry of earth resource formation
Almost everything we know about the cosmos has a foundation of research done here
Astrobiology is receiving increasing focus - Is there life elsewhere?
Earth is the only example with life in the universe - all we know comes from studies here
Understanding life and its history on Earth will help us ‘decipher’ what we see on other worlds
Brief History of Life on Earth
4.6 bya
3.5 bya
2.7 bya
2.1 bya
580 mya
530 mya
513 mya
430 mya
428 mya
425 mya
420 mya
418 mya
400 mya
370 mya
365 mya
359 mya
330 mya
310 mya
310 mya
228 mya
220 mya
200 mya
150 mya
130 mya
125 mya
55 mya
4.2 mya
190,000 ya
Earth’s birth
photoautotrophs (stromatolites)
eukaryotes (cells with nuclei)
algae fossils
metazoans (Ediacaran)
molluscans, arthropods, echinoderms, chordate (Cambrian)
oldest conodonts (vertebrates)
jawed fishes
oldest arthropod fossil on land
nonvascular land plant
oldest vascular plant
lobe finned fish
oldest insect
pteridosperms (seed ferns)
tetrapods (amphibian)
true forests (Carboniferous)
oldest amniote (reptile)
oldest flying insect
oldest synapsid
oldest dinosaur
oldest mammal
oldest pterosaur
oldest bird
oldest placental mammal
oldest flowering plant
first true primate
early hominin
modern humans
Have You Seen Any of These Magnificent Creatures?
Extinction Rules the Earth
25 significant extinction events have been identified
Estimated 99% of all species that ever existed are extinct
Estimated 10-14 million species today
Over 1 billion species have existed on earth and are gone
Earth has been a fantastic laboratory for new species experimentation
Extinction may be a critical ‘driver’ for evolution
Extinction clears ecosystems allowing rapid diversification & radiation of new species
Death provides opportunity
Therapsids/Permian
Archosaurs/Triassic
Dinosaurs/Jurassic-Cretaceous
Mammals/Now
Who?/Future
We owe our existence to extinctions
Extinction Causes
Asteroid & comet impacts
Earth’s astronomical cycles
Magnetic field reversals
Plate tectonics
Volcanism
Global warming & cooling
Glaciations & glacier melting
Sea level rise & fall
Ocean anoxia (lack of oxygen)
Methane clathrate release
Ocean euxinia (hydrogen sulfide release)
Ocean overturn - disruption of thermo-haline circulation
Nova, supernova, gamma ray burst
Life
Mass Extinctions
20% or more families ‘vanish’
Extends across all ecosystems
Sudden and short <1,000,000 years
Taxonomy - Classification of Life
The Big Five
17% families, 50% genera, 75% species
23% families, 48% genera, 70-75% species
57% families, 83% genera, 96% species
19% families, 50% genera, 70% species
27% families, 57% genera, 60-70% species
Permian World (299-251 million years ago)
Permian Climate
Early Permian: Still in ice age from late Carboniferous
Average global temperature ~12° C (54° F), O2 ~ 30%,
CO2 ~ 300ppm
Current global average temperature ~14° C (57° F)
Gradual warming melted ice by middle Permian
Drying & warming continued through late Permian
Much of interior became arid with wet and dry seasons, cool and dry periods
Carboniferous swamp forests replaced by conifers, seed ferns and drought tolerant
plants
Tropics were covered with swampy forests
Late Permian average global temperature ~21° C (70° F), O2 ~ 17%, CO2 ~ 1800ppm
Life on earth was diverse, vibrant and thriving on the land and in the seas
Permian Oceans
Permian Oceans
Permian Oceans
Eurypterids (Sea Scorpions)
Permian Reptiles
The Age of Reptiles began in the Permian.
Turtles, Tortoises, Terrapins
Archosaurs, Dinosaurs
Lizards, Snakes, Crocodilians, Birds
Pelycosaurs, Therapsids, Cynodonts, Dicynodonts
Mammals
Synapsids dominated the Permian land
Permian Land
Permian Land
Permian Land
Dicynodonts
herbivores
Gorgonopsians
Carnivores
The Victims
Foraminifera 97%
Amphibians 80%
Fusulinids 100%
Radiolaria (plankton) 99%
Reptiles 80%
Anthozoa (sea anemones, corals, etc.) 96%
Insects: 8-9 orders lost
Tabulate & rugose corals 100%
Bryozoans 79%
Fenestrates, trepostomes & cryptosomes 100%
Only mass extinction
Forests
Virtually disappeared
Brachipods 96%
Orthids & productids 100%
Bivalves 59%
Gastropods (snails) 98%
Ammonites 97%
Crinoids (echinoderm) 98%
Blastoids (echinoderm) 100%
Trilobites 100%
Eurypterids 100%
Ostracods (small crustaceans) 59%
Acanthodians 100%
Clue #1 - Stream Morphology
Meandering
Braided
Meandering and braided streams leave differing sedimentation patterns
Meandering stream channels are stabilized by vegetation
At P-T boundary meandering changed to braided
∴ At P-T boundary vegetation had decreased
Clue #2 - Coal Beds
Coal is the carbonized remains of plants from vast prehistoric forests and swamps
Extensive coal deposits were laid during the Carboniferous
To a lesser extent coal was deposited through the Permian
These coal deposits abruptly end at the P-T boundary
∴ The vigorous plant growth stopped
Clue #3 - Fungal Spore Level
Fungi are primary decomposers, reducing ‘the dead’ to carbon dioxide and water
Fungal spores in sediments tell a lot about the environment at the time
Change in fungal types and significant increase in fungal spore levels at P-T boundary
∴ Significant increase in decomposing biomass
Clue #4 - Sediment 13C/12C Ratio
Clue #4 - Sediment 13C/12C Ratio
Photosynthesis in plant preferentially incorporates slightly more 12CO2 than 13CO2
Atmosphere becomes slightly depleted in 12CO2 raising 13C/12C - reflected in sediments
Significant drop in 13C/12C at P-T boundary
Biogenic 12C removed by life had been returned to atmosphere
Decomposition of massive amounts of previous living biomass
Massive methane release
Photosynthesis not removing 12CO2
∴ Photosynthesis has essentially ceased
Clue #5 - Japanese Radiolarian Siliceous Oozes
Radiolaria are common protozoan zooplankton that produce silica skeletons
Skeletal remains make up a large part of the cover of the ocean floor as siliceous ooze
∴ Oceans became anoxic
Siberian Flood Basalt Volcanics
Massive eruptions of basaltic lavas
Form the basaltic traps
Mantle Plume Eruptions
Flood basalts
Mid-oceanic ridges
African rift valley
Hot spot volcanoes - Iceland, Hawaii
Basaltic Lava Eruption - Kilauea
Laki (Lakagigar) in Iceland 1783-4
June 8, 1783 to February 7, 1784 (8 months)
27 kilometer long fissure with 130 craters
Lava fountains 800 to 1400 m (2400 to 4200 ft) high
14 cubic kilometers of basaltic lava covering 565 square kilometers
Kilauea - 4 cubic kilometers in 30 years
304 million tons of carbon dioxide
120 million tons of sulfur dioxide
8 million tons of hydrogen fluoride
Carried 15 kilometers high by the convective eruption column
Chemistry
Carbon dioxide - CO2
Greenhouse gas can raise average global temperatures
Combines with water to form Carbonic Acid (weak acid) that can lower ocean pH
Lower pH can inhibit growth of animals that make CaCO3 structures
Laki eruption = 0.06 ppm CO2
Sulfur dioxide - SO2
Combines with water to form Sulfuric Acid (strong acid) and aerosol
Aerosol blocks sunlight causing cooling
1991 Pinatubo eruption: 0.5°C (0.9°F) global temperature reduction [1/6th Laki SO2]
Inhalation of aerosol causes pulmonary distress, fluid buildup in lungs, death
Very soluble in water and removed from atmosphere by rain
Resulting rain is acidic (acid rain)
Acid rain damages plants - base of the food chain
Hydrogen fluoride - HF
Causes skeletal fluorosis, deformation & embrittlement
Soluble in water, forming hydrofluoric acid - damaging to living tissue
Additional acid load in acid rain
Global Impact of Laki Eruption
Iceland
Grass growth stunted, fish catches decreased dramatically
80% of sheep, 50% of cattle, 50% of horses died from famine and HF/SO2 poisoning
Icelandic population decreased by 25% (10,000) famine and HF/SO2 poisoning
Europe
Heavy SO2 haze covered much of Western Europe
UK - 23,000 died from poisoning, 8,000 more from
famine
European death toll of 142,000
Monsoon Regions
Weakened African and Indian monsoon circulation
Low Nile River flow resulted in famine killing 1/6 of Egypt’s population
India - the Chalisa famine of 1783-4 resulted in 11 million deaths
North America
Winter 1783-4 longest and coldest on record
4.8°C below normal
Mississippi River froze as far south as New Orleans
Global death toll: 12,000,000 - deadliest eruption
in historical times
One of the most climatic and socially repercussive events of the last millennium
‘Thought Experiment’
Imagine
Laki eruption big enough to raise CO2 level 100 ppm (anthropologic CO2)
The eruption would be 1700 times bigger
SO2 would be 1700 times greater (10,200 times greater than Pinatubo)
For volcanic events, SO2 impact will dominate initially over CO2
It takes much longer for CO2 levels to increase to a level that will cause an effect
Now imagine even bigger - MUCH BIGGER - 20 TIMES BIGGER
Laki versus Siberian Basaltic Eruptions
Laki
Siberia
X-factor
Duration
8 Months
200,000 to 1 million years
6x105
Lava volume
14 cubic kilometers
2-4 million cubic kilometers
2x105
Lava area
565 square kilometers
4-7 million sq kilometers
1x105
Carbon dioxide 304 million tons (0.06 ppm) 55 trillion tons (10,000 ppm)
2x105
Sulfur dioxide
3x104
120 million tons
4 trillion tons
A series of multiple eruptions, not a single eruption.
Permian Extinction in a Single Chart
The Extinction (1)
Late Permian average global temperature ~21° C (70° F), O2 ~ 17%, CO2 ~ 1800ppm
Current global average temperature ~14° C (57° F)
Siberian eruptions eject massive amounts of CO2, SO2, HF, etc.
Local Siberian ecosystems exterminated by local high SO2, HF, etc.
The Extinction (2)
SO2 initiates rapid global cooling and a global volcanic ‘winter’
Plants/animals conditioned to warm climate stressed/killed by colder climate
Cold temperatures lower photosynthetic efficiency - plant growth reduced
Acid rain (undiluted lemon juice) causes more damage to plants
Base of food chain weakened
Acid run-off would begin stressing local continental shelf reef communities
The Extinction (3)
Greenhouse warming from atmospheric carbon eventually overcomes SO2 cooling
CO2 may have spiked to 7800ppm
Catastrophic global warming occurs
Atmospheric temperatures rise by 10 to 30° C (18 to 54° F)
Average temperatures of 26 to 46° C (79 to 115° F)
Dramatically high temperatures causes photosynthesis and food chain to collapse
Decimation of land plants and animals
Equatorial region and interior of Pangea becomes dry, hot, lifeless wasteland
The Extinction (4)
The huge ocean ecosystem exhibits significant chemical and temperature inertia
Negative impact lags those on land
Ocean surface temperatures rise and pH decreases (SO2, CO2)
Lower pH & higher temperatures inhibit growth of animals that make CaCO3 structures
Reef communities begin to collapse
Photosynthesis (phytoplankton, algae) also begins to collapse
Base of the marine food chain is being destroyed
Marine ecosystem begins to completely collapse
The Extinction (5)
Ocean circulation driven by temperature
gradients
Sinking and rising of ocean currents
oxygenates the ocean depths
During extinction ocean surface temperatures
become so high surface waters could not cool
enough to sink
Ocean circulation stopped
Oceans become anoxic, suffocating animal life
Anoxic conditions promote anaerobic bacterial growth
Anaerobic activity produces hydrogen sulfide (H2S), creating euxinic conditions
Hydrogen sulfide is very toxic, dealing the final blow to marine life
The Extinction (6)
Methanogenic bacteria in the deep cold oceans make methane that become trapped in
hydrates/clathrates
Methane clathrates are very sensitive to rising temperatures, releasing methane
Rising ocean temperatures caused release of methane from these ocean clathrates
Methane is 10X stronger greenhouse gas than CO2
Methane increases global temperatures, causing release of more methane…
This is a positive feedback loop
Earth came close to having a runaway global warming event that would have eradicated
all complex metazoan life
The Aftermath
Extinction took as long as 80,000 years to as short as 2,100 years
Greater than 80% of life on land; greater than 96% of marine life
Meishan Shangsi formation of South China
Sedimentary formation containing fossilized reef community spanning extinction event
Before the extinction:
333 species
After the extinction:
2 species
Extinction rate > 99%
The Aftermath
Earth was a very lonely and empty place
Environment: 21-24° C, 12-13% O2 (12-13,000 ft), 2000 ppm CO2
5 million years for ‘dead zone’ to become habitable
Total recovery time at least 10 million years
The first dinosaur from surviving archosaur
The first mammal from surviving therapsid
Four Simple Molecules
CO2, SO2, CH4, H2S
Found in molecular gas clouds where stars, and Earth, were and are created
The C, O, S, H, etc. in our bodies came from this molecular cloud
These simple molecules almost caused the extinction of all complex life on Earth
November 7, 2015
Cretaceous World - 65 MYA
Deccan flood basalt eruptions: 512,000 cubic kilometers
1/6th Siberian event