THE NEXT FOUR BILLION YEARS:
MAKING EARTH HABITABLE (FOR HUMANS)
Steve KeslerGeologicalSciences
EARTH – Special Features of Earth.
CONTINENTS
OCEAN
ATMOSPHERE
S Kesler, UMich
EARTH HISTORY –Evolution of continents, ocean, atmosphere. Evidence for life.
CONTINENTS
OCEAN
ATMOSPHERE
S Kesler, UMich
EARTH HISTORY – Geologic Time Scale
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
S Kesler, UMich
Mantle
Continental and Ocean Crust
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
Homogeneous Early Earth
HADEAN HISTORY
Core
Layered Earth
1 - Formation of the Core and Mantle - T=+30 M yrs
XS Kesler, UMich
http://www.meteorites21.com
Typical starting materialCHONDRITIC METEORITE
HADEAN HISTORY
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
CHONDRULES
1 - Formation of the Core and Mantle - T=+30 M yrs
S Kesler, UMich
http://www.psrd.hawaii.edu/
COREFe
MANTLEMg-Si-O
HADEAN HISTORY1 - Formation of the Core and Mantle - T=+30 M yrs
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
Core
Mantle
Continental and Ocean Crust
Heated byAccretion
Radioactivity
Melting
Iron sinks
~1000ºC
XS Kesler, UMich
HADEAN HISTORY
http://www.daviddarling.info/encyclopedia/P/protoplandisk.html
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
2 – Bombardment and Origin of Moon – T=+50 M yrs
SUN
PLANET
PLANETISSIMALS AND OTHER DEBRIS
S Kesler, UMich
HADEAN HISTORY
http://starchild.gsfc.nasa.gov
LARGE IMPACTORORIGIN OF MOON
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
MODEL OF IMPACT SEQUENCE
http://www.swri.edu/3pubs/ttoday/spring99/moon.htm
2 – Bombardment and Origin of Moon – T=+50 M yrs
S Kesler, UMich
H2O, CO2, H2
HADEAN HISTORY
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
?????
~0.1% H2Oand other
gases
3 – Formation of Early AtmosphereWater and gases
driven out bymelting
S Kesler, UMich
H2O, CO2, H2
HADEAN HISTORY
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
???
4 – Formation of the Ocean
EARTHCOOLED
THE GREAT RAIN
THE GREAT RAIN
OCEANS Kesler, UMich
H2O, CO2, H2
HADEAN HISTORY
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
4 – Formation of the Ocean
EARTHCOOLED
THE GREAT RAIN
THE GREAT RAIN
1 – VOLUME OF THE OCEAN2 – AGE OF THE OCEAN
???
OCEANS Kesler, UMich
http://www.geology.wisc.edu/zircon/
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic HADEAN HISTORY
5 – Formation of Early Crust - Jack Hills, Australia3.6 Billion Year Old
Conglomerate(Stream Gravel)
4.3 Billion Years Old
JOHN VALLEY
S Kesler, UMich
http://www.geology.wisc.edu/zircon/
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
3.6 Billion Year OldConglomerate
(Stream Gravel)
Zircon Grain(Zr2SiO4)
HADEAN HISTORY 5 – Formation of Early Crust - Jack Hills, Australia
4.3 Billion Years Old 100 μm S Kesler, UMich
http://www.geology.wisc.edu/zircon/
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
3.6 Billion Year OldConglomerate
(Stream Gravel)
Zircon Grain(Zr2SiO4)
HADEAN HISTORY 5 – Formation of Early Crust - Jack Hills, Australia
4.3 Billion Years Old 100 μm
4.3 Billion Years
S Kesler, UMich
http://earthweb.ess.washington.edu/~jelte/
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
~3.8 Billion Years Old
HADEAN HISTORY 5 – Formation of Early Crust – Isua, Greenland
S Kesler, UMich
http://www.denison.edu/geology/greene/
LAVA FLOW
Pillow-like shapeformed in water.
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
~3.8 Billion Years Old
HADEAN HISTORY 5 – Formation of Early Crust – Isua, Greenland
S Kesler, UMich
MANTLEMg-Si-O
MID-OCEANRIDGE
OCEANCRUST
Mg-Fe-Si-O
CONTINENTAL CRUSTNa-K-Ca-Al-Si-O
SUBDUCTIONZONE
PLATE TECTONICS AND RELATED PROCESSESOcean Crust at Mid-Ocean RidgesContinental Crust at Subduction Zones
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
1 - Growth of CrustARCHEAN AND PROTEROZOIC HISTORY
S Kesler, UMich
ZONE OFMELTING
AGE (BILLION YEARS)3.8 3.4 3.0 2.6 2.2 1.8 1.4 1.0 0.6 0.2
15
10
5 FREQ
UEN
CY
Condie et al., EPSL, 1998
Phan
er-
ozoic
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
ISUA
ARCHEAN AND PROTEROZOIC HISTORY2 - Supercontinent Cycles Build Continental Crust
S Kesler, UMich
H2O, CO2, H2
PROTEROZOIC HISTORY
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
1 – Formation of Oxygen-Bearing Atmosphere
NO O2!!
S Kesler, UMich
H2O, CO2, H2
PROTEROZOIC HISTORY
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
1 - Formation of Oxygen-Bearing Atmosphere
MOSTLIKELYSOURCE
Photosynthesis
6CO2 + 12H2O+ light energy →C6H12O6 + 6O2 + 6H2O
Cyanobacteria
NO O2!!
S Kesler, UMich
OXYGEN-RICHATMOSPHERE
DominatedBy Life
REDUCINGATMOSPHERE
DominatedBy Degassing
FORMATIONOF OZONE
Canfield, Ann Rev., 2005
PROTEROZOIC HISTORY1 - Formation of Oxygen-Bearing Atmosphere
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
2020.2
0.02
OXYGEN CONTENT (%)S Kesler, UMich
OXYGEN-RICHATMOSPHERE
DominatedBy Life
REDUCINGATMOSPHERE
DominatedBy Degassing
FORMATIONOF OZONE
Canfield, Ann Rev., 2005
PROTEROZOIC HISTORY1 - Formation of Oxygen-Bearing Atmosphere
Had
ean
Arc
hean
Prot
eroz
oic
BillionYears
Prec
ambr
ian
Phan
er-
ozoic
2020.2
0.02
OXYGEN CONTENT (%)
OLDEST FOSSILS
OLDEST CYANOBACTERIA FOSSILS
STROMATOLITE
S Kesler, UMich
SNOWBALLEARTH
http://www.arctic.uoguelph.ca
THREE FINAL ISSUES1 - Regulating Surface Temperatures
S Kesler, UMich
http://www.environment.sa.gov.au
The Greenhouse EffectH2O, CO2, CH4
THREE FINAL ISSUES1 - Regulating Surface Temperatures
S Kesler, UMich
THREE FINAL ISSUES1 - Regulating Surface Temperatures
S Kesler, UMich
http://solarsystem.nasa.gov/
VENUSEARTH
MARS
12°-24ºC 477°C
-53°CFailure on Other Rocky Planets
Average Surface Temperatures
RUNAWAYGREENHOUSE
ICEBOX
THREE FINAL ISSUES1 - Regulating Surface Temperatures
REGULATEDGREENHOUSE
S Kesler, UMich
http://www.gly.fsu.edu/~salters/GLY1000/
0 MILLIONS OF YEARS 180
http://web.mit.edu/mit-whoi/
THREE FINAL ISSUES2 - Formation of Mineral Deposits
Human life requiresmineral deposits
Formation of ocean crustat mid-ocean ridges
Seawater heatedat mid-ocean ridge
DEEP OCEAN FLOOR (5 km)
S Kesler, UMich
350ºCwater
containingmetal
sulfides
0.5
met
er
http://www.dfo-mpo.gc.ca/
Cross Section of Chimney
THREE FINAL ISSUES2 - Formation of Mineral Deposits DEEP OCEAN FLOOR (5 km)
S Kesler, UMich
http://www.dfo-mpo.gc.ca/
THREE FINAL ISSUES3 - Geologic Setting for Early Life
DEEP OCEAN FLOOR (5 km)Protected environment
TUBE WORMS
S Kesler, UMich
THREE FINAL ISSUES3 - Geologic Setting for Early Life
Russell et al., 2005, Economic Geology
DEEP OCEAN FLOORPROTECTED ENVIRONMENT
S Kesler, UMich
CONTINENTS
OCEAN
ATMOSPHERE
EARTH IS THE BEST PLACE TO START
S Kesler, UMich