Part I: Deformation mechanisms 1.What is “high temperature”? (3-11) 2. Diffusion Creep (3-23) ToDo 1: flow laws 3. Dislocation Creep (3-25) ToDo 2: Mechanism 4. Rocks: multi-scale materials (3-30) Maps Part I: Rheology & Dynamics ToDo 3: 0D shear 1. Stress, strain, forms of suffering (4-1) zones/ wires 2. Viscoelasticity, Thermodynamics (4-6) 3. Shear Zones (4-8) ToDo 4: 1-D Thermal 4. Thermal structure & strength profiles (4-13) profiles 5. Strength profiles 2. (4-15) ToDo 5: Strength Part I: Applications Profiles 1.Toroidal (San Andreas, revisited) (4-20) 2. Collisions (Alps / Himalaya)? (4-22) 3. Rifts (Basin & Range vs EAR) (4-27) 4. Project talks (4-29) lecture Emphasis on concepts, processes and quantitative tools to think about how plates deform... with applications at the end... do
T Independent Projects*: ToDo 1: flow laws 3 groups of 2? ToDo 2: Mechanism Maps* 1 on wire deformation experiments ToDo 3: 0D shear zones/wires 2 on regional studies ToDo 4: 1-D Thermal (each person on a profiles* different aspect? e.g. thermal structure/ ToDo 5: Strength seismic velocities/ Profiles* viscosity and surface deformation patterns) EXAM*: conceptual questions, not calculations *Graded
empirical, ab initio , observation/ mechanistic, experiment, deductive inductive phenomenological The word " empirical " denotes information gained by means of observation, experience, or experiment... The standard positivist view of empirically acquired information has been that observation, experience, and experiment serve as neutral arbiters between competing theories. However, since the 1960s, Thomas Kuhn [2] has promoted the concept that these methods are influenced by prior beliefs and experiences. Consequently it cannot be expected that two scientists when observing, experiencing, or experimenting on the same event will make the same theory-neutral observations. The role of observation as a theory-neutral arbiter may not be possible. Theory-dependence of observation means that, even if there were agreed methods of inference and interpretation, scientists may still disagree on the nature of empirical data. (Wikipedia: Empirical ) The term phenomenology in science is used to describe a body of knowledge which relates empirical observations of phenomena to each other, in a way which is consistent with fundamental theory, but is not directly derived from theory.... The boundaries between theory and phenomenology, and between phenomenology and experiment, are fuzzy. Some philosophers of science, and in particular Nancy Cartwright argue that any fundamental laws of Nature are merely phenomenological generalizations[2] (Wikipedia: Phenomenology_(science) ) A calculation is said to be ab initio (or "from first principles") if it relies on basic and established laws of nature without additional assumptions or special models. (Wikipedia: Ab_initio)
from the siesmogenic layer down and the asthenosphere up..
Part I: Deformation mechanisms 1.What is “high temperature”? (3-11) 2. Diffusion Creep (3-23) 3. Dislocation Creep (3-25) 4. Rocks: multi-scale materials (3-30) Questions: By what processes do rocks deform at high temperature ?
atomic scale silicon metal, atomic force microscopy ~1 nm http://www.omicron.de/
“dislocation” scale Dislocations in olivine from Hawaiian mantle nodule. Optical view, scale ~175 microns images source: http://ic.ucsc.edu/~casey/eart150/Lectures/DefMech/14deformationmechanisms.htm
“grain” scale from T. Hiraga http://www.eri.u-tokyo.ac.jp/hiraga/Preface.html grain boundary:
deformation mechanism map 45678#94&"#:5;<=8#> 8 ! = ' ! " ! " " ! =7< ! ? dislocation creep ! & ! & = ! # ! @ 1/$# ! "#)2%+))#,34&0 ;7< ! % ! % ! A ! " ! & ; diffusion ! !$ $ ! ! ! ;6 ! % creep 67< ! # ! ! ;= 6 ! " ! & ! ;? " ! ! 67< ! !$ ! ! !# ! % ! ;@ ! ; ' 6 ; = 8 ? log !"#$%&'(#)'*+#,-'.%/()0
Microstructure of a * not from here, but representative fabric mylonite. Fine- grained quartz-rich matrix surrounding relative rigid feldspar clasts. 1 cm width of view. * rock * “fabric” Undulose extinction in larger quartz Recrystalization grains microstructure. reflection Relatively strain- dislocations free grains with in crystal. straight grain Width of boundaries. Width view 4 mm of view 2 mm. (CASEY) image source: http://ic.ucsc.edu/~casey/eart150/Lectures/DefMech/14deformationmechanisms.htm
SW Ontario, from website of Chris Gerbi, University of Maine, Orono
Questions: Part II: Rheology & Dynamics >How do we extrapolate micro-mechanisms to the 1. Stress, strain, forms of suffering (4-1) Earth? 2. Viscoelasticity (Cheese), Thermodynamics (4-6) >How do we describe (mechanically) deformation in 3. Shear Zones (4-8) the Earth ? 4. Thermal structure & strength profiles (4-13) >What are the structures and dynamics that lie 5. Strength profiles 2. (4-15) beneath the seismogenic regions? >How do we infer processes at depth from the patterns of seismicity?
1. Stress, strain, forms of suffering (4-1) e=0.375 Z ! =3.6982 X Y
2. Viscoelasticity, Cheese and Thermodynamics of Deformation (4-6) viscoelasticity, anelasticity and attenuation... rheology: phenomenological models
3. Shear Zones (4-8) How do mylonites (ductile shear zones) form? Why and does strain localize? emphasis on grain size reduction... Zero-D shear zone: Montesi, Geophysical Research Letters, 2007
The Wire Deformation Experiments: Work and Strain Energy � = � L � = F strain stress elasticity � = E � L A Consider increasing stress from 0 to � SE = 1 = 1 � � d � 2 �� LA Strain energy 2 V 1. Constant force W = Fu = 1 2. vary mass and material 2 � A � L work 3. measure displacement, time So in this case. W=SE, 0=-W+SE , a conservative system 4. analyze data with thermodynamic model
(McKenzie, Jackson & Priestley, EPSL 2005) Continental geotherms, constrained by P-T estimates of xenolith equilibration 4. Thermal structure & strength profiles (4-13) )'%% )$%% /+61+7:/87+34; <34)4=034$%4=0 <4:/4>" ! ?"@" (from Equations of state and thermal conductivity) )&%% )%%% % &% $% '% (% )%% )&% )$% )'% )(% &%% ' Density, pressure and temperature 17+--87+3491: $ & % % &% $% '% (% )%% )&% )$% )'% )(% &%% $ *+,-./0 !"# ! % &% $% '% (% )%% )&% )$% )'% )(% &%% *+1/23456
Temperature, °C The Structure and Physical Properties of the Earth’s Crust, Geophysical Monograph 14, editor John G. Heacock, pp. 169 – 184, 1971. The Thermal Structure of the Continental Crust DAVID D . BLACKWELL measured heat flow at surface estimated temperatures at a depth of 6 kilometers http://smu.edu/geothermal/heatflow/ http://www1.eere.energy.gov/geothermal/geomap.html
5. Strength profiles 2. (4-15)
5. Strength profiles 2. (4-15) Return to this image:
Part III: Applications 1.Toroidal (San Andreas, revisited) (4-20) 2. Collisions (Alps / Himalaya)? (4-22) 3. Rifts (Basin & Range / EAR) (4-27) 4. Project talks (4-29) Thermal/compositional differences that lead to rheological differences? Boundary condition differences (i.e. plate forces) ? Feedbacks between the two? How to develop hypotheses for rheological explanations for morphological/structural differences in a setting? How to test those hypotheses?
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