Earth sciences overview Chris Paola email@example.com 4-8025 SAFL & Pills 30b
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
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
The Ancient Kingdoms • Mineralogy & petrology • Structural geology • Paleontology • Igneous, metamorphic, sedimentary geology • Surficial and Quaternary geology • Geophysics • Geochemistry • Geobiology
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
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
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?
Mechanism: how plates bend The theory describing plate deflection is identical to that used for beams in structural engineering!
Alternative Earth: Mesozoic greenhouse • Warm, ice-free poles • High CO2 • Weak oceanic, atmospheric circulation • Oceanic anoxic events • Land initially assembled as one ‘supercontinent’
The Earth in equilibrium • Atmospheric temperature • Steady state erosion • Steady state deposition
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?
Example: earthquake distribution follows Gutenberg-Richter law An example of a “power law” – a common distribution
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…)
Non-linearity: self-organization & pattern formation • Plate tectonics • Fault systems • Banding in minerals • River networks • Bedforms and bars Canyonlands, UT Rio Salado, NM
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
Trends and culture • Research trends: • Crossing disciplines, e.g. emergence of geobiology • Quantification & theory • New methods • Major limitations: • Access to information • Age control
New methods New research made possible by new measurement techniques LIDAR
New methods High-res bathymetry
New methods Dating methods for surface materials and short time scales Cosmogenic radionuclides (CRN)
New methods Geomicrobiology
New methods High res 3D seismic reflection
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
Research frontiers • Drivers and history of plate tectonics • Role of life? • Atmospheric history and regulation • Role of life? • Origin of life
Connections • Civil engineering: hydrology, geomorphology, structural geology, rock mechanics • Ecology: geobiology, paleoecology • Computer science: data bases and data mining; numerical earth modeling
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.
Milankovitch orbital cycles 2. Axial tilt (obliquity) Period: 40,000 years Range: 2.4 degrees Present value: 23.44 degrees
Milankovitch orbital cycles 3. Precession Period: 20,000 years Range: entire orbit Present value: perihelion during SH summer, aphelion during NH summer
Milankovitch orbital cycles: linear superposition but nonlinear Earth response
Milankovitch orbital cycles: linear superposition but nonlinear Earth response Vostok ice core data