Earth sciences overview

1. Earth sciences overview Chris Paola cpaola@umn.edu 4-8025 SAFL & Pills 30b

2. Plan for next two weeks • Today: overview of earth sciences • Friday: Nonlinearity and nonequilibrium case examples • Monday: paleoclimate (with Emi Ito) • Friday: ESci connections to other fields

3. Journals and societies • American Geophysical Union (Eos, Journal of Geophysical Research, Water Resources Research) • Nearly all areas of earth science: atmosphere, oceans, surface (inc. hydrology), geobiology, lithosphere, deep earth) • Geological Society of America (Geology, GSA Today, GSA Bulletin) • All areas of geology, geobiology, and geochemistry • European Geophysical Union • Terra Nova

4. The Ancient Kingdoms • Mineralogy & petrology • Structural geology • Paleontology • Igneous, metamorphic, sedimentary geology • Surficial and Quaternary geology • Geophysics • Geochemistry • Geobiology

5. Research threads • Observation and inference on planetary scales: atmosphere, ocean, deep interior • Mechanical properties & materials • Extreme conditions (e.g. heat, pressure) • Extreme events (e.g. meteorite impact) • Co-evolution of Earth and life • Spatial structure through time: surface • Spatial structure through time: lithosphere • Comparative planetology

6. Major intellectual contributions • Uniformitarianism: present as key to past • Deep time, evolution, age of Earth • Plate tectonics • “Mechanism”: application of physical laws over planetary scales • Neocatastrophism • Alternative earths and planetary history: past as key to (possible) futures

7. Uniformitarianism

9. Deep time: the highlights reel

10. Plate tectonics

11. Plate tectonics & topography

12. Plate tectonics: basement

13. Plate tectonics: a simple estimation problem • Plate horizontal motion rates: of the order of cm/year • Relation of vertical to horizontal rates: order 0.1 • What (order of magnitude) should be the concentration of sediment in river water?

14. Mechanism: how plates bend The theory describing plate deflection is identical to that used for beams in structural engineering!

15. Alternative Earth: Mesozoic greenhouse • Warm, ice-free poles • High CO2 • Weak oceanic, atmospheric circulation • Oceanic anoxic events • Land initially assembled as one ‘supercontinent’

16. The Earth in equilibrium • Atmospheric temperature • Steady state erosion • Steady state deposition

17. Non equilibrium – the variability around the mean • It’s hard to think of examples of geologic systems that don’t fluctuate: • Stream flow • Plate motion (earthquakes) • Sedimentation • Heat flow (volcanoes) • Erosion rates • One basic question is: what is the distribution of fluctuation energy over time and/or space scales?

18. Example: earthquake distribution follows Gutenberg-Richter law An example of a “power law” – a common distribution

19. Example: flood distribution

20. Nonlinearity: Earth sciences have provided the type examples for three major classes of new nonlinear phenomena of C20 • Fractals: coastline of Britain (contour line) • Chaos: simplified atmospheric model • Self-organized criticality: sand pile (a few minor problems…)

21. Non-linearity: self-organization & pattern formation • Plate tectonics • Fault systems • Banding in minerals • River networks • Bedforms and bars Canyonlands, UT Rio Salado, NM

22. Trends and culture • Dominant influence of finding resources • Minerals • Fossil fuels: coal, hydrocarbons • water • From story-telling to advanced mathematics • Wavelet analysis invented in geophysics • Historical tradition – we like a ‘good story’ • Induction vs deduction – detectives vs theorists • Central role of field work • Is prediction possible? How to test models in historical sciences

23. Trends and culture • Research trends: • Crossing disciplines, e.g. emergence of geobiology • Quantification & theory • New methods • Major limitations: • Access to information • Age control

24. New methods New research made possible by new measurement techniques LIDAR

25. New methods High-res bathymetry

26. New methods Dating methods for surface materials and short time scales Cosmogenic radionuclides (CRN)

27. New methods Geomicrobiology

28. New methods High res 3D seismic reflection

29. Research frontiers • Complexity, natural variability, and predictability • Natural variability in surface morphology • Can we forecast earthquakes? Floods? • Big problem seems to be systems that are too random to simulate directly, too ordered to use only statistics • Long-range connections (“teleconnections”) in the Earth system • Ocean/atmosphere coupling • Deep earth/surface earth coupling – does erosion cause mountain belts? • Role of microbes

30. Research frontiers • Drivers and history of plate tectonics • Role of life? • Atmospheric history and regulation • Role of life? • Origin of life

31. Connections • Civil engineering: hydrology, geomorphology, structural geology, rock mechanics • Ecology: geobiology, paleoecology • Computer science: data bases and data mining; numerical earth modeling

32. Milankovitch orbital cycles 1. Eccentricity Circular orbit, no eccentricity. Orbit with 0.5 eccentricity Periods: 413,000, 95,000, and 136,000 years. Overall dominant ~ 100,000 year cycle Range: -0.03 to +0.02). Present value: 0.017.

33. Milankovitch orbital cycles 2. Axial tilt (obliquity) Period: 40,000 years Range: 2.4 degrees Present value: 23.44 degrees

34. Milankovitch orbital cycles 3. Precession Period: 20,000 years Range: entire orbit Present value: perihelion during SH summer, aphelion during NH summer

35. Milankovitch orbital cycles: linear superposition but nonlinear Earth response

36. Milankovitch orbital cycles: linear superposition but nonlinear Earth response Vostok ice core data