Palaeomagnetism, plates, hot spots, trenches and ridges are the subject of this unusual book. Plate Tectonics is a book of exercises and background information that introduces and demonstrates the basics of the subject. In a lively and lucid manner, it brings together a great deal of material in spherical trigonometry that is necessary to understand plate tectonics and the research literature written about it. It is intended for use in first year graduate courses in geophysics and tectonics, and provides a guide to the quantitative understanding of plate tectonics.
Author(s): Allan Cox, R. B. Hart
Edition: 1
Publisher: Wiley-Blackwell
Year: 1986
Language: English
Pages: 418
Tags: Plate Tectonics;Geology;Earth Sciences
Preface xiii
Introduction xvii
1 Basics ofa Revolution 1
Earth's Layers 1
Core, Mantle, and Crust 1
Strength of the Mantle 3
Plate Tectonic Layering 5
Plate Geometry 8
Euler Poles 12
Defining Euler Poles 12
Finding Euler Poles 14
Isochrons and Velocities 17
Magnetic Stripes 17
Rates of Spreading 18
Rises 21
Discovery and Descriptions 22
Theories Before seafloor Spreading and Plate Tectonics 24
Plate Tectonic Explanation of Rises 24
Explanation of High Topography 25
Initiation of Rises 27
Trenches and Island A«s 28
Discovery and Description 28
Plate Tectonic Explanation 29
Fracture Zones 33
Discovery & Description 33
Plate Tectonic Explanation 35
Velocity Fields 36
Putting Plate Tectonics to Work 39
Problems 42
Suaested Readings 49
Texts 49
Classic Papers SO
Plate Tectonics on a Plane SO
Geology of Rises and Trenches SO
2 Plates in Velocity Space 51
The Velocity Line 51
The Velocity Plane 57
Plates In Velocity Space 64
TripleJundloDS 73
Problems 80
Suaested Readings 83
Plate Tectonics on a Plane 83
Veloclry Space 83
Triple Junctions B4
Mendocino Triple Junction B4
Juan de Fuca Plate B4
3 Getting Around on a Sphere 85
CIrcles on a Sphere 85
Spherical Coorcllnates 87
Fixed Reference Frame 88
Rotation about Axis 3 91
Rotation about Axis 2 93
Distance Between Two Points 9S
Cartesian Coordinates 104
Constructing Projections 114
Azimuthal Projealons 114
Polar Projections 117
Constructing Polar Projections 119
Constructing Equatorial Projections 119
The Mercator Projection 120
Problems 124
Suggested Readings 125
General 125
4 Wrapping Plate Tectonics Around a Globe 127
Transform Trend 128
Slip vectors 130
Velocities Due to Rotation about an Euler Pole 131
Spreading Velocities on the Mid-Atlantic Ridge 135
Best Fit Determined by Least Squares 138
Angu1ar Velocity Vectors 142
Velocity Space on the Globe 145
Rules of Angular Velocity Vectors 147
Checking Internal Consistency 148
Angular Velocity Space 151
Finding the Local Velocity V From the Angular Velocity 154
Problems 156
Suggested Readings 157
General 157
Sources of Data 158
5 Plotting Planes and Vectors in Local Coordinates 159
Inclination and Declination 160
Local Cartesian Components 163
Faults and Slip Vectors 164
Problems 174
Suggested Readings 176
6 Earthquakes and Plates 177
Birth of an Earthquake 177
First Motion 182
Going Three Dimensional 190
Directions of Compression and Tension 197
Curved Ray Paths Through a Spherical Earth 200
Earthquakes at Transforms 201
Earthquakes at Ridges 203
Earthquakes at Trenches 207
Problems 212
Suggested Readings 217
7 Finite Rotations 219
Jumping Poles 221
Finite Rotations Versus Angular Velocity Vectors 234
Rules of Finite Rotations 237
Analyzing Data 241
Finding Stage Poles from Two Reconstruction Poles 241
Finding Instantaneous Rates 244
Finding Intermediate Positions Between Two Total Reconstruction Poles 245
Global CircuitS 247
Finite Rotations in a HotSpot Reference Frame 251
The Three·Plate Probiem 255
Problems 258
Suggested Readings 260
Texts 260
Sources of Data 260
8 Magnetism and Isochrons 263
Earth's Magnetic Field 263
How Rocks Get Magnetized 266
Depositional Remanent Magnetization (DRM) 267
Thermoremanent Magnetization (TRM) 268
Good and Bad Magnetic Memories 271
Magnetic Cleaning 273
Reversals of the Earth's Magnetic Field 273
Discovery of Reversals 273
ACritical Experiment 275
What Causes the Earth's Magnetic Field? 276
What Causes Reversals? 279
Magnetostratigraphy 280
Geomagnetic Reversal Time Scale From K·Ar Dating 280
Polarity Intervals 282
Reversal Tune Scale from Marine Magnetic Anomalies 282
Fidelity and Resolution 284
Calibration 285
Superchrons 285
Problems 292
Suggested Readings 29S
Classic Papers on Reversal Time Scale 295
Current Papers on Magnetic Stratigraphy 295
Classic Papers on Magnetic Stripes 295
9 Paleomagnetic Poles 297
Obtaining Geographic Coordinates from Paleomagnetic Data 298
Magnetic Latitude and Colatitude 298
Dipole Field Observed on the Surface of a Sphere 299
Secular Variations 300
Nuts and Bolts of Paleomagnetism 302
Has Spain Rotated? 302
Experimental Strategy 303
Selection of Formations to be Samples 303
Volcanics 303
Sediments 304
Red beds 30S
Limestones 305
Intrusives 306
Collecting Samples 306
Measurement and Magnetic Cleaning 307
Statistical Analysis 309
Tectortic Corrections 312
Virtual Geomagnetic Poles and Paleomagnetic Poles 313
Confidence Limits 317
Vindication 318
Polar wander and Plate Motion 320
Using Paleomagnetic Poles to Validate Plate Reconstruction 322
Displaced Terranes 327
Apparent Polar wander Paths 328
Problems 331
Suggested Readings 335
Standard Texts 335
Articles 335
10 Putting It All Together 337
What Drives the Plates? 337
Passive Versus Active Plates 338
First Test: Ridge Offsets 340
Second Test:Jumping and Propagating Ridges 341
Third Test: Ridge Meets Trench 341
Rerum Flow in the Asthenosphere 342
Driving Forces 343
Mantle Drag Force For 343
Ridge Push FRP 344
Slab Pull Force Fsp 345
Slab Drag Force FSD 345
Transform Fault Resistance FTF 345
Colliding Resistance FeR 345
Suction Force Fsu 346
Motion Relative to the Mantle 346
Velocity Versus Plate Area 347
velocity Versus Length of Transforms 348
Velocity Versus Length of Ridges 348
Velocity Versus Length of Subducting Slab 349
Velocity Versus Continental Area of Plates 350
AModel for What Drives the Plate 351
Absolute Plate Motion 3S4
Three Model PlanetS 354
Planet A 354
Planet B 355
Planet C 355
No Net Torque 356
Planet Earth 358
HOISpOlS 358
Planet Awith HotSpots 358
Planets B and C with HOISpOlS 360
Planet Earth with HotSpotS 360
AConsistency Test 362
Single-Plate Torque Due to Slab Pull 363
Paleomagnetic Euler Poles 366
Some Concluding Thoughts 367
True Polar Wander 369
AThought Experiment 369
Observations on Planet Earth 371
Paleomagnetic and HotSpo< Euler Poles 373
Ufe Cyles ofa Plate 374
Are Continental Plates Intrinsically Slow? 374
Tracks and Cusps 375
Velocities of Continental Plates 375
Life Cycle of Oceanic and Continental Plates 376
Problems 379
SUggested Readings 379
Plate Driving Forces 379
Flow in the Asthenosphere 380
Whole Mantle Convection 380
Absolute Plate Motion from Single-Plate Torque 380
Absolute Plate Motion from HotspotS 381
True Polar Wander 381
Index 383
Index of References 391
