THE NEXT
FOUR BILLION YEARS:
MAKING EARTH HABITABLE
(FOR HUMANS)
Steve Kesler
Geological
Sciences
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
Phanerozoic
Precambrian
Proterozoic
Archean
Hadean
Billion
Years
S Kesler, UMich
EARTH HISTORY – Geologic Time Scale
Phanerozoic
HADEAN HISTORY
1 - Formation of the Core and Mantle - T=+30 M yrs
Billion
Years
Precambrian
Hadean
Archean
Proterozoic
Homogeneous Early Earth
S Kesler, UMich
Layered Earth
Mantle
Core
X
Continental and Ocean Crust
Phanerozoic
Proterozoic
Precambrian
Archean
Typical starting material
CHONDRITIC METEORITE
CHONDRULES
Hadean
Billion
Years
HADEAN HISTORY
1 - Formation of the Core and Mantle - T=+30 M yrs
S Kesler, UMich
http://www.meteorites21.com
Phanerozoic
~1000ºC
MANTLE
Mg-Si-O
Melting
Precambrian
Archean
Proterozoic
Heated by
Accretion
Radioactivity
Hadean
Billion
Years
HADEAN HISTORY
1 - Formation of the Core and Mantle - T=+30 M yrs
S Kesler, UMich
Iron sinks
CORE
Fe
Mantle
Core
http://
www.psrd.hawaii.edu/
X
Continental and Ocean Crust
Phanerozoic
HADEAN HISTORY
2 – Bombardment and Origin of Moon – T=+50 M yrs
Billion
Years
Precambrian
Hadean
Archean
Proterozoic
SUN
S Kesler, UMich
PLANET
PLANETISSIMALS
AND OTHER DEBRIS
http://www.daviddarling.info/encyclopedia/P/protoplandisk.html
Phanerozoic
MODEL OF IMPACT SEQUENCE
Precambrian
Archean
Proterozoic
LARGE IMPACTOR
ORIGIN OF MOON
Hadean
Billion
Years
HADEAN HISTORY
2 – Bombardment and Origin of Moon – T=+50 M yrs
S Kesler, UMich
http://www.swri.edu/
3pubs/ttoday/spring99/moon.htm
http://starchild.gsfc.nasa.gov
Phanerozoic
Proterozoic
Water and gases
driven out by
melting
Precambrian
H2O, CO2, H2
Hadean
Archean
HADEAN HISTORY
3 – Formation of Early Atmosphere
Billion
?????
Years
S Kesler, UMich
~0.1% H2O
and other
gases
Phanerozoic
Proterozoic
H2O, CO2, H2
Precambrian
Archean
HADEAN HISTORY
4 – Formation of the Ocean
EARTH
COOLED
THE
THE
GREAT
GREAT
RAIN
RAIN
Billion
Years
Hadean
???
S Kesler, UMich
OCEAN
Phanerozoic
Proterozoic
H2O, CO2, H2
Precambrian
Archean
HADEAN HISTORY
4 – Formation of the Ocean
EARTH
COOLED
THE
THE
GREAT
GREAT
RAIN
RAIN
Billion
Years
Hadean
???
S Kesler, UMich
OCEAN
1 – VOLUME OF THE OCEAN
2 – AGE OF THE OCEAN
Phanerozoic
HADEAN HISTORY
5 – Formation of Early Crust - Jack Hills, Australia
Billion
Years
Precambrian
Hadean
Archean
Proterozoic
JOHN VALLEY
S Kesler, UMich
4.3 Billion Years Old
http://www.geology.wisc.edu/zircon/
3.6 Billion Year Old
Conglomerate
(Stream Gravel)
Phanerozoic
HADEAN HISTORY
5 – Formation of Early Crust - Jack Hills, Australia
Billion
Years
Precambrian
Zircon Grain
(Zr2SiO4)
Hadean
Archean
Proterozoic
3.6 Billion Year Old
Conglomerate
(Stream Gravel)
S Kesler, UMich
4.3 Billion Years Old
http://www.geology.wisc.edu/zircon/
100 μm
Phanerozoic
HADEAN HISTORY
5 – Formation of Early Crust - Jack Hills, Australia
Billion
Years
Precambrian
Zircon Grain
(Zr2SiO4)
Hadean
Archean
Proterozoic
3.6 Billion Year Old
Conglomerate
(Stream Gravel)
S Kesler, UMich
4.3 Billion Years
4.3 Billion Years Old
http://www.geology.wisc.edu/zircon/
100 μm
Phanerozoic
HADEAN HISTORY
5 – Formation of Early Crust – Isua, Greenland
Billion
Years
Precambrian
Hadean
Archean
Proterozoic
~3.8 Billion Years Old
S Kesler, UMich
http://earthweb.ess.washington.edu/~jelte/
Phanerozoic
HADEAN HISTORY
5 – Formation of Early Crust – Isua, Greenland
LAVA FLOW
Billion
Years
Precambrian
Hadean
Archean
Proterozoic
Pillow-like shape
formed in water.
S Kesler, UMich
~3.8 Billion Years Old
http://www.denison.edu/geology/greene/
Phanerozoic
Precambrian
Archean
Proterozoic
PLATE TECTONICS AND RELATED PROCESSES
Ocean Crust at Mid-Ocean Ridges
Continental Crust at Subduction Zones
Hadean
Billion
Years
ARCHEAN AND PROTEROZOIC HISTORY
1 - Growth of Crust
S Kesler, UMich
MID-OCEAN
RIDGE
OCEAN
CRUST
Mg-Fe-Si-O
CONTINENTAL CRUST
Na-K-Ca-Al-Si-O
SUBDUCTION
ZONE
MANTLE
Mg-Si-O
Phanerozoic
ARCHEAN AND PROTEROZOIC HISTORY
2 - Supercontinent Cycles Build Continental Crust
Billion
Years
S Kesler, UMich
10
ISUA
3.8
3.4
5
ZONE OF
MELTING
3.0 2.6 2.2
1.8
1.4 1.0
AGE (BILLION YEARS)
FREQUENCY
Precambrian
Hadean
Archean
Proterozoic
15
0.6 0.2
Condie et al., EPSL, 1998
Phanerozoic
Proterozoic
H2O, CO2, H2
Precambrian
Archean
NO O2!!
Hadean
Billion
Years
PROTEROZOIC HISTORY
1 – Formation of Oxygen-Bearing Atmosphere
S Kesler, UMich
Phanerozoic
Proterozoic
H2O, CO2, H2
Precambrian
Archean
NO O2!!
Hadean
Billion
Years
PROTEROZOIC HISTORY
1 - Formation of Oxygen-Bearing Atmosphere
S Kesler, UMich
MOST
LIKELY
SOURCE
Photosynthesis
6CO2 + 12H2O
+ light energy →
C6H12O6 + 6O2 + 6H2O
Cyanobacteria
Phanerozoic
PROTEROZOIC HISTORY
1 - Formation of Oxygen-Bearing Atmosphere
Precambrian
20
2
0.2
S Kesler, UMich
REDUCING
ATMOSPHERE
Dominated
By Degassing
0.02
Billion
Years
OXYGEN-RICH
ATMOSPHERE
Dominated
By Life
Hadean
Archean
Proterozoic
FORMATION
OF OZONE
OXYGEN CONTENT (%)
Canfield, Ann Rev., 2005
Phanerozoic
PROTEROZOIC HISTORY
1 - Formation of Oxygen-Bearing Atmosphere
OXYGEN-RICH
ATMOSPHERE
Dominated
By Life
Precambrian
Archean
Proterozoic
FORMATION
OF OZONE
OLDEST CYANOBACTERIA FOSSILS
STROMATOLITE
REDUCING
ATMOSPHERE
Dominated
By Degassing
20
2
0.2
S Kesler, UMich
0.02
Billion
Years
Hadean
OLDEST FOSSILS
OXYGEN CONTENT (%)
Canfield, Ann Rev., 2005
THREE FINAL ISSUES
1 - Regulating Surface Temperatures
SNOWBALL
EARTH
S Kesler, UMich
http://www.arctic.uoguelph.ca
THREE FINAL ISSUES
1 - Regulating Surface Temperatures
The Greenhouse Effect
H2O, CO2, CH4
S Kesler, UMich
http://www.environment.sa.gov.au
THREE FINAL ISSUES
1 - Regulating Surface Temperatures
S Kesler, UMich
THREE FINAL ISSUES
1 - Regulating Surface Temperatures
Failure on Other Rocky Planets
-53°C
ICEBOX
Average Surface Temperatures
12°-24ºC
REGULATED
GREENHOUSE
EARTH
S Kesler, UMich
MARS
477°C
RUNAWAY
GREENHOUSE
VENUS
http://solarsystem.nasa.gov/
THREE FINAL ISSUES
2 - Formation of Mineral Deposits
Human life requires
mineral deposits
DEEP OCEAN FLOOR (5 km)
Seawater heated
at mid-ocean ridge
Formation of ocean crust
at mid-ocean ridges
http://web.mit.edu/mit-whoi/
0
S Kesler, UMich
MILLIONS OF YEARS
180
http://www.gly.fsu.edu/~salters/GLY1000/
THREE FINAL ISSUES
2 - Formation of Mineral Deposits DEEP OCEAN FLOOR (5 km)
0.5 meter
350ºC
water
containing
metal
sulfides
Cross Section of Chimney
S Kesler, UMich
http://www.dfo-mpo.gc.ca/
THREE FINAL ISSUES
3 - Geologic Setting for Early Life
DEEP OCEAN FLOOR (5 km)
Protected environment
TUBE WORMS
S Kesler, UMich
http://www.dfo-mpo.gc.ca/
THREE FINAL ISSUES
DEEP OCEAN FLOOR
3 - Geologic Setting for Early Life PROTECTED ENVIRONMENT
S Kesler, UMich
Russell et al., 2005, Economic Geology
EARTH IS THE BEST PLACE TO START
CONTINENTS
OCEAN
ATMOSPHERE
S Kesler, UMich