Extensional Tectonics E-Book
161,99 €
Mehr erfahren.
- Herausgeber: John Wiley & Sons
- Kategorie: Wissenschaft und neue Technologien
- Serie: Geophysical Monograph Series
- Sprache: Englisch
A synthesis of current knowledge on global extensional tectonics
The extension of Earth’s lithosphere occurs at divergent plate boundaries as well as in plate interiors. The geological, geochemical, and sedimentary processes of extension offer insights into topics ranging from the fundamentals of tectonics to the evolution of life.
Extensional Tectonics: Rifting and Continental Extension reviews present-day knowledge of extensional tectonic processes and explores examples from around the world.
Volume highlights include:
- Overview of extensional tectonic processes from continental rifting to oceanic basin formation
- In-depth examination of extension along rift systems and rift margins
- Review of post-collisional continental extension
- Examples from Africa, Asia, Europe, and the Americas
- Insights from observations, modeling, and 3D seismic data interpretation of extended terrains
This book is one of a set of three in the collection Tectonic Processes: A Global View.
Browse the first volume, Compressional Tectonics: Plate Convergence to Mountain Building.
The American Geophysical Union promotes discovery in Earth and space science for the benefit of humanity. Its publications disseminate scientific knowledge and provide resources for researchers, students, and professionals.
Sie lesen das E-Book in den Legimi-Apps auf:
Seitenzahl: 1137
Veröffentlichungsjahr: 2025
Ähnliche
Table of Contents
Cover
Table of Contents
Series Page
Title Page
Copyright Page
LIST OF CONTRIBUTORS
PREFACE
TECTONIC PROCESSES: A GLOBAL VIEW
EXTENSIONAL TECTONICS
ACKNOWLEDGMENTS
1 Processes and Perspectives in Extensional Tectonics
1.1. INTRODUCTION
1.2. THE IMPORTANCE OF EXTENSIONAL TECTONICS
1.3. TERMINOLOGY AND COMMON MISCONCEPTIONS
1.4. OBJECTIVES AND ORGANIZATION OF THE BOOK
ACKNOWLEDGMENTS
AVAILABILITY STATEMENT
REFERENCES
Part I: Large‐Scale Extensional Tectonics
2 The East African Rift System
2.1. INTRODUCTION
2.2. STRUCTURE OF THE EARS
2.3. PLATE STRUCTURE AND PATTERN OF EARTHQUAKES
2.4. THE MANTLE AND MELT GENERATION
2.5. VOLCANOLOGY AND GEOTHERMAL RESOURCES OF THE EAST AFRICAN RIFT
2.6. INTO THE FUTURE
ACKNOWLEDGMENTS
REFERENCES
3 Geological and Geophysical Constraints Guide New Tectonic Reconstruction of the Gulf of Mexico
3.1. INTRODUCTION
3.2. GEOLOGIC HISTORY
3.3. INTEGRATED GEOPHYSICAL MODELING
3.4. SPATIAL ANALYSIS OF GRAVITY AND MAGNETIC DATA AND MAPPED TECTONIC FEATURES
3.5. TECTONIC RECONSTRUCTION OF THE BASIN
3.6. CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
4 Introduction to an Active Oblique Rift: Walker Lane–Gulf of California
4.1. INTRODUCTION TO THE WALKER LANE–GULF OF CALIFORNIA OBLIQUE RIFT
4.2. PLATE TECTONIC SETTING OF THE WALKER LANE–GULF OF CALIFORNIA OBLIQUE RIFT
4.3. WALKER LANE—THE FIRST STAGE: OBLIQUE CONTINENTAL RIFTING
4.4. GULF OF CALIFORNIA—THE SECOND STAGE: SEAFLOOR SPREADING AND OBLIQUE CONTINENTAL MARGIN
4.5. CONCLUSIONS
ACKNOWLEDGMENTS
AVAILABILITY STATEMENT
REFERENCES
5 Extensional Tectonics in Western Anatolia, Turkey: Eastward Continuation of the Aegean Extension
5.1. INTRODUCTION
5.2. GEOLOGICAL BACKGROUND
5.3. OUTSTANDING QUESTIONS IN AEGEAN TECTONICS
5.4. CONCLUSIONS
ACKNOWLEDGMENTS
AVAILABILITY STATEMENT
REFERENCES
Part II: Extensional Tectonic Processes
6 Oceanic Isostasy
6.1. INTRODUCTION
6.2. PLATE DRIVING FORCES
6.3. OCEANIC ISOSTASY
6.4. LOCALIZATION OF SPREADING CENTERS
6.5. GEOLOGICAL EXAMPLES
6.6. OCEANIC VERSUS CONTINENTAL TECTONICS
6.7. OUTSTANDING ISSUES
6.8. SUMMARY POINTS
ACKNOWLEDGMENTS
AVAILABILITY STATEMENT
REFERENCES
7 Rigidity‐Seismicity Relation in the East African Rift System
7.1. INTRODUCTION
7.2. TECTONIC SETTING
7.3. DATA
7.4. METHODS
7.5. RESULTS AND DISCUSSION
7.6. MODEL UNCERTAINTY
7.7. CONCLUSION
ACKNOWLEDGMENTS
REFERENCES
8 Edge‐Driven Convection‐Based Models for Evolution of the Mississippi Embayment and Associated Alkaline Magmatism
8.1. INTRODUCTION
8.2. GEOLOGIC OVERVIEW
8.3. METHODS
8.4. RESULTS
8.5. DISCUSSION
8.6. CONCLUSIONS
REFERENCES
Part III: Case Studies of Continental Extensional Tectonics
9 Rapid Versus Delayed Linkage and Coalescence of Interacting Rift Tips
9.1. INTRODUCTION
9.2. METHODS
9.3. RESULTS
9.4. DISCUSSION
9.5. CONCLUSIONS
ACKNOWLEDGMENTS
AUTHOR CONTRIBUTIONS
AVAILABILITY STATEMENT
REFERENCES
10 Root Problem of Mid‐Tertiary Cordilleran Detachment Faults
10.1. INTRODUCTION
10.2. GEOLOGIC AND REGIONAL BACKGROUND
10.3. WHIPPLE DETACHMENT FAULT SYSTEM
10.4. METHODS
10.5. RESULTS
10.6. DISCUSSION
10.7. CONCLUSIONS
ACKNOWLEDGMENTS
AVAILABILITY STATEMENT
REFERENCES
11 Büyük Menderes Graben in Western Turkey
11.1. INTRODUCTION
11.2. GEOLOGIC OVERVIEW
11.3. STRATIGRAPHY AND STRUCTURAL OVERVIEW OF THE BMG
11.4. STRUCTURAL GEOLOGY
11.5. DATA AND METHODOLOGY
11.6. SEISMIC INTERPRETATIONS
11.7. KINEMATIC EVOLUTION AND SUBSIDENCE HISTORY
11.8. DISCUSSION
11.9. CONCLUSIONS
ACKNOWLEDGMENTS
REFERENCES
12 Transfer Zones in Extended Terranes
12.1. INTRODUCTION
12.2. NOMENCLATURE AND BACKGROUND OF TRANSFER ZONES
12.3. GEOLOGICAL BACKGROUND
12.4. SOME LOCAL‐SCALE TRANSFER ZONES (FAULTS)
12.5. REGIONAL‐SCALE TRANSFER ZONES IN WESTERN ANATOLIA
12.6. DISCUSSION
12.7. CONCLUSIONS
ACKNOWLEDGMENTS
AVAILABILITY STATEMENT
REFERENCES
INDEX
End User License Agreement
List of Tables
Chapter 1
Table 1.1 Extensional plate boundaries.
Table 1.2 Back‐arc extensional systems related to subduction.
Chapter 3
Table 3.1 The list of tectonic constraints used for each reconstruction per...
Table 3.2 Kinematic parameters determined from tectonic reconstruction in F...
Chapter 5
Table 5.1 A summary of some dates of granitic assemblages that intrude the ...
Table 5.2 Summary of some dates of granitic assemblages that intrude the Ta...
Table 5.3 A summary of some dates of granitic assemblages associated with r...
Table 5.4 Summary of some dates of granitic assemblages that intrude the Ce...
Table 5.5 Summary of some dates of granitic assemblages that intrude into t...
Table 5.6
Summary of some dates of granitic assemblages that intrude the Rho...
Table 5.7 Brief summary of some dates from granitic assemblages that intrud...
Table 5.8 Brief summary of some dates of granitic assemblages that intrude ...
Table 5.9 List of selected earthquake events along the Simav Fault and asso...
Table 5.10 List of selected earthquake events along the Aegean‐Anatolian pl...
Chapter 7
Table 7.1 Material parameters used for the computation of geotherms and str...
Table 7.2 Properties of the compartments shown in Figure 7.2a.
Chapter 8
Table 8.1 Whole‐rock analyses of igneous rocks from AAP numbers, central Ar...
Table 8.2 Whole‐rock Nd isotopic composition of AAP lamprophyres.
Table 8.3 Summarized zircon (U‐Th)/He data.
Chapter 9
Table 9.1 Field data on slip vectors on border faults used for the kinemati...
Chapter 10
Table 10.1 List of metamorphic core complexes associated with the southwest...
Table 10.2 Bulk rock compositions (molar wt %) from samples analyzed in thi...
Table 10.3 Results of Th‐Pb monazite ages for samples analyzed in this stud...
Chapter 12
Table 12.1 Faults, fault zones, segments, depressions, and grabens discusse...
List of Illustrations
Chapter 1
Figure 1.1 Global multiresolution topography map.Divergent plate boundar...
Figure 1.2 The cartoon cross‐section illustrates the main plate boundary typ...
Figure 1.3 Map of the Great African Rift Valley. Numbers on the plate bounda...
Figure 1.4 (a) Map of the western portion of the United States, showing the ...
Figure 1.5 World Stress Map (2016). The stress map shows the maximum horizon...
Figure 1.6 Examples of extension and normal fault tectonics in subduction zo...
Chapter 2
Figure 2.1 Generalized map of the East African Rift System. Major faults are...
Figure 2.2 Simplified conceptual illustration of the shallow crustal structu...
Figure 2.3 (a) Inset map showing the locations of panels B and C in the East...
Figure 2.4 (a) Distribution of earthquakes in East Africa from the EHB globa...
Figure 2.5 (a) Crustal scale cross‐section of the magma‐rich Main Ethiopian ...
Figure 2.6 Tomographic cross‐sections from the core‐mantle boundary to the s...
Figure 2.7 Cartoons illustrating different conceptual models of magma genera...
Chapter 3
Figure 3.1 (a) The first vertical derivative of the gravity field from Sandw...
Figure 3.2 Seismic cross‐sections (data courtesy of TGS) illustrating variou...
Figure 3.3 (a) Residual gravity field (original data from Sandwell et al., 2...
Figure 3.4 Simplified geologic time chart listing the major tectonic events ...
Figure 3.5 (a) Key tectonic structures mentioned in the literature and inter...
Figure 3.6 Filtered residual potential fields data. (a) Residual Bouguer gra...
Figure 3.7 Tectonic reconstructions of the GoM using GPlates version 2.2 and...
Chapter 4
Figure 4.1 Map of the Walker Lane–Gulf of California oblique rift. The first...
Figure 4.2 Examples of the superb exposures in the Walker Lane–Gulf of Calif...
Figure 4.3 Plate tectonic setting for the Walker Lane–Gulf of California obl...
Figure 4.4 Late Miocene to Holocene transtensional arc and rift volcanism (1...
Figure 4.5 Simplified depiction of faults and basins formed under orthogonal...
Figure 4.6 Case study of oblique rift basins in the Walker Lane (Busby et al...
Figure 4.7 Simplified map of Late Cenozoic rocks of the Baja California Peni...
Figure 4.8 Schematic representation of stratigraphic, structural, intrusive,...
Chapter 5
Figure 5.1 Tectonic map of the Aegean and Anatolian microplates. Plate bound...
Figure 5.2 Geological map of Western Anatolia focusing on the ophiolite and ...
Figure 5.3 North‐south generalized cross‐section across western Turkey after...
Figure 5.4 Geological map showing structures and locations of Western Anatol...
Figure 5.5 (a) A simplified geologic map of the Sivrihisar Massif (eastern T...
Figure 5.6 Paleogeographic reconstruction of Western Anatolia (center box) a...
Figure 5.7 (a) Map of the Simav Fault and associated structures. Small dots ...
Figure 5.8 North‐south generalized cross‐section through the Hellenic arc sy...
Figure 5.9 (a) EMODnet Digital Bathymetry map with some structures overlain....
Figure 5.10 (a) Cross‐section of the Aegean anomaly interpreted as the Afric...
Figure 5.11 Map of plate boundaries between the Aegean and Anatolian micropl...
Figure 5.12 (a) Interpretative thrust sequence during the formation of Anato...
Figure 5.13 Isochemical phase diagrams with overlapping garnet core composit...
Figure 5.14 Snapshots of thermal models of the Çine nappe for the (a) tecton...
Chapter 6
Figure 6.1 Figure from Hayford (1911) / American Association for the Advance...
Figure 6.2 Asthenosphere isostatic response to surface mass exchange that oc...
Figure 6.3 Subaerial and submarine square root of age (a) and mass gain (b) ...
Figure 6.4 Calculations for 1D across‐axis isostatic response of differentia...
Figure 6.5 Example of two axes of extension. (a) Thermal age across the syst...
Figure 6.6 Examples of random thermal structure of a rift and isostatic resp...
Figure 6.7 Morphology of the mid‐ocean ridge system across the Icelandic pla...
Figure 6.8 Isostatic gravity anomaly of Iceland and surrounding region (Bonv...
Figure 6.9 Seismicity and slip vectors for extensional earthquakes on and ar...
Figure 6.10 1D calculations of mantle tractions for a representative oceanic...
Figure 6.11 Gulf of California topography (a) and free‐air gravity anomaly (...
Figure 6.12 South Atlantic plate reconstructions at 120 and 115 Ma from Hein...
Figure 6.13 Bathymetry of the Marianas (a) and Okinawa Trough (b) back‐arc s...
Figure 6.14 Diffuse plate boundaries from Stein and Sella (2002) / with perm...
Chapter 7
Figure 7.1 Topographic map of eastern Africa and Arabia. Red lines show the ...
Figure 7.2 (a) Surface heat flow data in the EARS. Black rectangles indicate...
Figure 7.3 Gravity disturbance from the EIGEN 6C4 geopotential model (Förste...
Figure 7.4 Gravity signals of the topography (a), crust (b), and sediment (c...
Figure 7.5 Temperature model at depths of 20 (a) and 50 km (b) for a dry rhe...
Figure 7.6 Temperature model at depths of 20 (a) and 50 km (b) for a wet rhe...
Figure 7.7 Sensitivity of geotherms with changes of the heat production valu...
Figure 7.8 Residual mantle gravity anomalies in the EARS.
Figure 7.9 Integrated lithospheric strength at depths of 20 (a) and 50 km (b...
Figure 7.10 Integrated lithospheric strength at depths of 20 (a) and 50 km (...
Figure 7.11 Integrated lithospheric strength at depths of 20 (a) and 50 km (...
Figure 7.12 (a) Geotherms and (b) lithospheric strengths for four representa...
Figure 7.13 (a) Geotherms and (b) lithospheric strengths for four representa...
Chapter 8
Figure 8.1 Map of the south‐central United States, with regional tectonic fe...
Figure 8.2 Digital elevation maps and geologic overlays for (a) the OFB with...
Figure 8.3 Schematic diagrams indicating the current structure of the Missis...
Figure 8.4 Summary plot of age data presented in previous studies (Biotite A...
Figure 8.5 SiO
2
versus (Na
2
O + K
2
O) discrimination diagram adapted from Midd...
Figure 8.6 Na
2
O versus K
2
O discrimination diagram (fields adapted from Stopp...
Figure 8.7 Harker plots of MgO (%) versus (a) Al
2
O
3
, (b) SiO
2
, (c) K
2
O, (d) ...
Figure 8.8 AFM diagram adapted from Irvine and Baragar (1971), with A = Na
2
O...
Figure 8.9 Trace element spider diagrams normalized to primitive mantle and ...
Figure 8.10 Trace element ratio diagrams for the studied samples including (...
Figure 8.11 Trace element ratio diagrams for the studied samples including (...
Figure 8.12
143
Nd/
144
Nd isotopic ratio plots for all eight provinces of the ...
Figure 8.13 Backscattered electron images of 11 samples: (a) AB1909, (b) AB1...
Figure 8.14 Digital elevation map of central Arkansas with overlain polygons...
Figure 8.15 Digital elevation map of central Arkansas with basement faults (...
Figure 8.16 La/Sm versus Sr and Nb plots that demonstrate the effects of car...
Figure 8.17 Schematic diagrams indicating a time‐progressive evolution for t...
Figure 8.18 Schematic diagrams indicating a time‐progressive evolution for t...
Chapter 9
Figure 9.1 Cartoon illustrating the evolution of zones of rift segment inter...
Figure 9.2 Topographic relief map of the East African Rift System (EARS; Sou...
Figure 9.3 (a) Topographic relief map of southern Malawi and central Mozambi...
Figure 9.4 Topographic relief profiles. (a, c) 30 m resolution Shuttle Radar...
Figure 9.5 Model setup to simulate landscape evolution across two contiguous...
Figure 9.6 Field photographs showing slip surfaces along the Chingale Step F...
Figure 9.7 (a) Displacement field, (b) modeled topography, and (c) drainage ...
Figure 9.8 (a) Displacement field, (b) modeled topography, and (c) drainage ...
Figure 9.9 (a) Plot comparing the along‐axis model surface relief, model top...
Figure 9.10 (a–f) Model results of predicted static Coulomb stress change di...
Chapter 10
Figure 10.1 Map of the North American Cordilleran Anatectic Belt and metamor...
Figure 10.2 Map illustrating the distribution of Pelona‐Orocopia‐Rand Schist...
Figure 10.3 Simplified geologic map of the Whipple Mountains based on a comp...
Figure 10.4 (a–c) Models of detachment‐fault‐system evolution: (a) Gans et a...
Figure 10.5 Three end‐member models for the emplacement of the Orocopia schi...
Figure 10.6 Plot of age (Ma) versus depth (km), aiming to illustrate the tra...
Figure 10.7 (a) Landscape photograph of the Whipple Mountains highlighting a...
Figure 10.8 Outcrop photographs illustrate the styles of deformation within ...
Figure 10.9 Garnet‐bearing metapelite samples. (a) Sample VJ‐03‐01‐20‐1A, a ...
Figure 10.10 (a) Backscattered electron (BSE) image of a Whipple Mountains g...
Chapter 11
Figure 11.1 Generalized tectonic map of the Aegean extensional province. The...
Figure 11.2 (a) Generalized geological map of western Turkey. (b) Geological...
Figure 11.3 3D tectonic models and cross‐sections showing the Cenozoic exten...
Figure 11.4 Generalized geological map of the BMG and surrounding areas in w...
Figure 11.5 Generalized stratigraphic column of the Büyük Menderes Graben ar...
Figure 11.6 (a) 3D view of the 11 seismic reflection profiles from a PETREL;...
Figure 11.7 Synthetic seismogram generation. The synthetic is shown with the...
Figure 11.8 Velocity values used for the velocity model for each formation o...
Figure 11.9 The structural cross‐section restoration workflow in 2D Move sof...
Figure 11.10 Depth converted uninterpreted (a) and interpreted (b) and balan...
Figure 11.11 Restoration steps showing (a) polygon creation for seismic prof...
Figure 11.12 (a) Unfolding of balanced horizons to remove the deformation of...
Figure 11.13 (a) Restoration of the late Miocene Aydin Formation (orange uni...
Figure 11.14 (a) Restoration of the middle Miocene Bascayir Formation (blue ...
Figure 11.15 Isochore maps showing Miocene sedimentary (Aydin and Bascayir f...
Figure 11.16 Initiation of the south‐dipping boundary fault and its antithet...
Figure 11.17 (a) Formation of the high‐angle synthetic faults that superimpo...
Figure 11.18 (a) Deposition of the Bascayir Formation, thickening toward the...
Figure 11.19 (a) Deposition of the Huseyinciler Formation in the Pliocene. (...
Figure 11.20 (a) Tectonic subsidence rates during the deposition of each for...
Figure 11.21 3D diagrams showing extensional evolution of the Menderes metam...
Chapter 12
Figure 12.1 Examples of some transfer zone geometries. (a) Morley et al. (19...
Figure 12.2 Tectonic map of the Aegean and Anatolian microplates. Plate boun...
Figure 12.3 Geological map of Western Anatolia focusing on the ophiolite and...
Figure 12.4 Map of the Menderes Massif. İAESZ, İzmir‐Ankara‐Erzincan suture ...
Figure 12.5 A map of northern Turkey and the NASZ shows major strands' locat...
Figure 12.6 Map of the northern (Gördes) and portions of the central (Ödemiş...
Figure 12.7 (a) Map across Gediz Graben documenting WNW‐oriented normal and ...
Figure 12.8 Map of the İBTZ from the cities of İzmir and Balıkesir only. Bou...
Figure 12.9 Block diagrams showing the nature of the İBTZ. (a) Uzel et al. (...
Figure 12.10 Map of the UMTZ from the cities of Uşak and Muğla only. The zon...
Figure 12.11 Cartoon of how extension can be accommodated as the process pro...
Guide
Cover Page
Table of Contents
Series Page
Title Page
Copyright Page
LIST OF CONTRIBUTORS
PREFACE
Begin Reading
INDEX
Wiley End User License Agreement
Pages
ii
iii
iv
vii
viii
ix
x
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
351
352
353
354
355
356
357
358
Geophysical Monograph Series
240 Chemostratigraphy Across Major Chronological ErasAlcides N. Sial, Claudio Gaucher, Muthuvairavasamy Ramkumar, and Valderez Pinto Ferreira (Eds.)
241 Mathematical Geoenergy: Discovery, Depletion, and RenewalPaul Pukite, Dennis Coyne, and Daniel Challou (Eds.)
242 Ore Deposits: Origin, Exploration, and ExploitationSophie Decree and Laurence Robb (Eds.)
243 Kuroshio Current: Physical, Biogeochemical and Ecosystem DynamicsTakeyoshi Nagai, Hiroaki Saito, Koji Suzuki, and Motomitsu Takahashi (Eds.)
244 Geomagnetically Induced Currents from the Sun to the Power GridJennifer L. Gannon, Andrei Swidinsky, and Zhonghua Xu (Eds.)
245 Shale: Subsurface Science and EngineeringThomas Dewers, Jason Heath, and Marcelo Sánchez (Eds.)
246 Submarine Landslides: Subaqueous Mass Transport Deposits From Outcrops to Seismic ProfilesKei Ogata, Andrea Festa, and Gian Andrea Pini (Eds.)
247 Iceland: Tectonics, Volcanics, and Glacial FeaturesTamie J. Jovanelly
248 Dayside Magnetosphere InteractionsQiugang Zong, Philippe Escoubet, David Sibeck, Guan Le, and Hui Zhang (Eds.)
249 Carbon in Earth’s InteriorCraig E. Manning, Jung‐Fu Lin, and Wendy L. Mao (Eds.)
250 Nitrogen Overload: Environmental Degradation, Ramifications, and Economic CostsBrian G. Katz
251 Biogeochemical Cycles: Ecological Drivers and Environmental ImpactKaterina Dontsova, Zsuzsanna Balogh‐Brunstad, and Gaël Le Roux (Eds.)
252 Seismoelectric Exploration: Theory, Experiments, and ApplicationsNiels Grobbe, André Revil, Zhenya Zhu, and Evert Slob (Eds.)
253 El Niño Southern Oscillation in a Changing ClimateMichael J. McPhaden, Agus Santoso, and Wenju Cai (Eds.)
254 Dynamic Magma EvolutionFrancesco Vetere (Ed.)
255 Large Igneous Provinces: A Driver of Global Environmental and Biotic ChangesRichard. E. Ernst, Alexander J. Dickson, and Andrey Bekker (Eds.)
256 Coastal Ecosystems in Transition: A Comparative Analysis of the Northern Adriatic and Chesapeake BayThomas C. Malone, Alenka Malej, and Jadran Faganeli (Eds.)
257 Hydrogeology, Chemical Weathering, and Soil FormationAllen Hunt, Markus Egli, and Boris Faybishenko (Eds.)
258 Solar Physics and Solar WindNour E. Raouafi and Angelos Vourlidas (Eds.)
259 Magnetospheres in the Solar SystemRomain Maggiolo, Nicolas André, Hiroshi Hasegawa, and Daniel T. Welling (Eds.)
260 Ionosphere Dynamics and ApplicationsChaosong Huang and Gang Lu (Eds.)
261 Upper Atmosphere Dynamics and EnergeticsWenbin Wang and Yongliang Zhang (Eds.)
262 Space Weather Effects and ApplicationsAnthea J. Coster, Philip J. Erickson, and Louis J. Lanzerotti (Eds.)
263 Mantle Convection and Surface ExpressionsHauke Marquardt, Maxim Ballmer, Sanne Cottaar, and Jasper Konter (Eds.)
264 Crustal Magmatic System Evolution: Anatomy, Architecture, and Physico‐Chemical ProcessesMatteo Masotta, Christoph Beier, and Silvio Mollo (Eds.)
265 Global Drought and Flood: Observation, Modeling, and PredictionHuan Wu, Dennis P. Lettenmaier, Qiuhong Tang, and Philip J. Ward (Eds.)
266 Magma Redox GeochemistryRoberto Moretti and Daniel R. Neuville (Eds.)
267 Wetland Carbon and Environmental ManagementKen W. Krauss, Zhiliang Zhu, and Camille L. Stagg (Eds.)
268 Distributed Acoustic Sensing in Geophysics: Methods and ApplicationsYingping Li, Martin Karrenbach, and Jonathan B. Ajo‐Franklin (Eds.)
269 Congo Basin Hydrology, Climate, and Biogeochemistry: A Foundation for the Future (English version)Raphael M. Tshimanga, Guy D. Moukandi N’kaya, and Douglas Alsdorf (Eds.)
269 Hydrologie, climat et biogéochimie du bassin du Congo: une base pour l’avenir (version française)Raphael M. Tshimanga, Guy D. Moukandi N’kaya, et Douglas Alsdorf (Éditeurs)
270 Muography: Exploring Earth’s Subsurface with Elementary ParticlesLászló Oláh, Hiroyuki K. M. Tanaka, and Dezsö Varga (Eds.)
271 Remote Sensing of Water‐Related HazardsKe Zhang, Yang Hong, and Amir AghaKouchak (Eds.)
272 Geophysical Monitoring for Geologic Carbon StorageLianjie Huang (Ed.)
273 Isotopic Constraints on Earth System ProcessesKenneth W. W. Sims, Kate Maher, and Daniel P. Schrag (Eds.)
274 Earth Observation Applications and Global Policy FrameworksArgyro Kavvada, Douglas Cripe, and Lawrence Friedl (Eds.)
275 Threats to Springs in a Changing World: Science and Policies for ProtectionMatthew J. Currell and Brian G. Katz (Eds.)
276 Core‐Mantle Co‐Evolution: An Interdisciplinary ApproachTakashi Nakagawa, Madhusoodhan Satish‐Kumar, Taku Tsuchiya, and George Helffrich (Eds.)
277 Compressional Tectonics: Plate Convergence to Mountain Building (Tectonic Processes: A Global View, Volume 1)Elizabeth J. Catlos and İbrahim Çemen (Eds.)
278 Extensional Tectonics: Rifting and Continental Extension (Tectonic Processes: A Global View, Volume 2)İbrahim Çemen and Elizabeth J. Catlos (Eds.)
279 Strike‐Slip Tectonics: Oceanic Transform Faults to Continental Plate Boundaries (Tectonic Processes: A Global View, Volume 3)İbrahim Çemen and Elizabeth J. Catlos (Eds.)
280 Landscape Fire, Smoke, and Health: Linking Biomass Burning Emissions to Human Well‐BeingTatiana V. Loboda, Nancy H. F. French, and Robin C. Puett (Eds.)
281 Clouds and Their Climatic Impacts: Radiation, Circulation, and PrecipitationSylvia Sullivan and Corinna Hoose (Eds.)
282 Fast Processes in Large‐Scale Atmospheric Models: Progress, Challenges, and OpportunitiesYangang Liu and Pavlos Kollias (Eds.)
283 Helicities in Geophysics, Astrophysics, and BeyondKirill Kuzanyan, Nobumitsu Yokoi, Manolis K. Georgoulis, and Rodion Stepanov (Eds.)
284 Noisy Oceans: Monitoring Seismic and Acoustic Signals in the Marine EnvironmentGaye Bayrakci and Frauke Klingelhoefer (Eds.)
285 Alfvén Waves Across Heliophysics: Progress, Challenges, and OpportunitiesAndreas Keiling (Ed.)
286 Salt in the Earth Sciences: Evaporite Rocks and Salt DepositionWebster Mohriak
287 Salt in the Earth Sciences: Basin Analysis and ApplicationsWebster Mohriak
288 Microanalysis of Atmospheric Particles: Techniques and ApplicationsJoseph M. Conny and Peter R. Buseck (Eds.)
289 Distributed Acoustic Sensing in Borehole GeophysicsYingping Li, Robert Mellors, and Ge Zhan (Eds.)
290 Tectonics and Seismic Structure of Alaska and Northwestern Canada: EarthScope and BeyondNatalia A. Ruppert, Margarete A. Jadamec, and Jeffrey T. Freymueller (Eds.)
Geophysical Monograph 278
Extensional Tectonics
Rifting and Continental Extension
Tectonic Processes: A Global View, Volume 2
Editors
İbrahim ÇemenElizabeth J. Catlos
This Work is a co‐publication of the American Geophysical Union and John Wiley and Sons, Inc.
This edition first published 2025© 2025 American Geophysical Union
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, except as permitted by law. Advice on how to obtain permission to reuse material from this title is available at http://www.wiley.com/go/permissions.
Published under the aegis of the AGU Publications Committee
Matthew Giampoala, Vice President, PublicationsSteven A. Hauck, II, Chair, Publications CommitteeFor details about the American Geophysical Union visit us at www.agu.org.
The right of İbrahim Çemen and Elizabeth J. Catlos to be identified as the editors of this work has been asserted in accordance with law.
Registered OfficeJohn Wiley & Sons, Inc., 111 River Street, Hoboken, NJ 07030, USA
Editorial Office111 River Street, Hoboken, NJ 07030, USA
For details of our global editorial offices, customer services, and more information about Wiley products visit us at www.wiley.com.
Wiley also publishes its books in a variety of electronic formats and by print‐on‐demand. Some content that appears in standard print versions of this book may not be available in other formats.
Limit of Liability/Disclaimer of WarrantyWhile the publisher and authors have used their best efforts in preparing this work, they make no representations or warranties with respect to the accuracy or completeness of the contents of this work and specifically disclaim all warranties, including without limitation any implied warranties of merchantability or fitness for a particular purpose. No warranty may be created or extended by sales representatives, written sales materials or promotional statements for this work. The fact that an organization, website, or product is referred to in this work as a citation and/or potential source of further information does not mean that the publisher and authors endorse the information or services the organization, website, or product may provide or recommendations it may make. This work is sold with the understanding that the publisher is not engaged in rendering professional services. The advice and strategies contained herein may not be suitable for your situation. You should consult with a specialist where appropriate. Further, readers should be aware that websites listed in this work may have changed or disappeared between when this work was written and when it is read. Neither the publisher nor authors shall be liable for any loss of profit or any other commercial damages, including but not limited to special, incidental, consequential, or other damages.
Library of Congress Cataloging‐in‐Publication DataNames: Çemen, Ibrahim, 1951‐ editor. | Catlos, Elizabeth J., 1971‐ editor.Title: Extensional tectonics : rifting and continental extension / editors Ibrahim C¸emen, Elizabeth J. Catlos.Description: Hoboken, NJ : Wiley, 2025. | Series: Geophysical monograph series | Includes index.Identifiers: LCCN 2024039058 (print) | LCCN 2024039059 (ebook) | ISBN 9781119773740 (hardback) | ISBN 9781119773771 (adobe pdf) | ISBN 9781119773764 (epub)Subjects: LCSH: Geology, Structural. | Rifts (Geology)Classification: LCC QE601. E98 2025 (print) | LCC QE601 (ebook) | DDC 551.8–dc23/eng/20240929LC record available at https://lccn.loc.gov/2024039058LC ebook record available at https://lccn.loc.gov/2024039059
Cover design: WileyCover image: © Gerald Corsi/Getty Images
LIST OF CONTRIBUTORS
Ian D. BastowDepartment of Earth Science and EngineeringImperial College LondonLondon, United Kingdom
Elizabeth A. BellDepartment of Earth and Space SciencesUniversity of CaliforniaLos Angeles, California, USA
Erin BeutelDepartment of Geology and Environmental GeosciencesCollege of CharlestonCharleston, South Carolina, USA
Cathy J. BusbyDepartment of Earth and Planetary SciencesUniversity of California at DavisDavis, California, USA
Elizabeth J. CatlosJackson School of GeosciencesDepartment of Earth and Planetary SciencesUniversity of Texas at AustinAustin, Texas, USA
İbrahim ÇemenDepartment of Geological SciencesUniversity of AlabamaTuscaloosa, Alabama, USA
James A. ConderSchool of Earth Systems and SustainabilitySouthern Illinois UniversityCarbondale, Illinois, USA
Zuze DulanyaGeography and Earth Sciences DepartmentUniversity of MalawiZomba, Malawi
Thomas M. EtzelJackson School of GeosciencesDepartment of Earth and Planetary SciencesUniversity of Texas at AustinAustin, Texas, USAandExxonMobilParkway Spring, Texas, USA
Irina FilinaDepartment of Earth and Atmospheric SciencesUniversity of Nebraska–LincolnLincoln, Nebraska, USA
Karen FontijnDepartment of Geosciences, Environment and SocietyUniversité Libre de BruxellesBrussels, Belgium
James GranathGranath and Associates Consulting GeologyHighland Ranch, Colorado, USA
Valeria JaramilloDepartment of Earth and Space SciencesUniversity of California, Los AngelesLos Angeles, California, USA
Derek KeirDepartment of Ocean and Earth ScienceUniversity of SouthamptonSouthampton, United KingdomandDepartment of Earth SciencesUniversity of FlorenceFlorence, Italy
Folarin KolawoleDepartment of Earth and Environmental SciencesColumbia UniversityNew York, USA
Rezene MahatsenteSchool of GeosciencesUniversity of Louisiana at LafayetteLafayette, Louisiana, USA
Nicholas MariitaGeothermal Energy Training and Research InstituteDedan Kimathi University of TechnologyNyeri, Kenya
Osman MereyDepartment of Geological SciencesUniversity of AlabamaTuscaloosa, Alabama, USA
James D. MuirheadSchool of EnvironmentUniversity of AucklandAuckland, New Zealand
Keith PutirkaDepartment of Earth and Environmental SciencesCalifornia State UniversityFresno, California, USA
Tyrone O. RooneyDepartment of Earth and Environmental SciencesMichigan State UniversityEast Lansing, Michigan, USA
Axel K. SchmittInstitute of Earth SciencesHeidelberg UniversityHeidelberg, GermanyandJohn de Laeter CentreCurtin UniversityBentley, Australia
Daniel StockliJackson School of GeosciencesDepartment of Earth and Planetary SciencesUniversity of Texas at AustinAustin, Texas, USA
Berry H. Tew, Jr.Department of Geological SciencesUniversity of AlabamaTuscaloosa, Alabama, USAandGeological Survey of AlabamaTuscaloosa, Alabama, USA
Samuel R. WalkerDepartment of Geological SciencesUniversity of AlabamaTuscaloosa, Alabama, USA
Bernhard WeiseSchool of Geography, Geology and the EnvironmentUniversity of LeicesterLeicester, United Kingdom
Matthew W. WielickiDepartment of Geological SciencesUniversity of AlabamaTuscaloosa, Alabama, USA
Liang XueDepartment of Earth and Environmental SciencesSyracuse UniversitySyracuse, New York, USA
An YinDepartment of Earth and Space SciencesUniversity of CaliforniaLos Angeles, California, USA
PREFACE
TECTONIC PROCESSES: A GLOBAL VIEW
Tectonic processes control the shape and structure of the Earth, and these processes affect the Earth's climate, geomorphology, magmatism, geochemistry, sedimentary environments, and economic resources. The evolution of these features through geologic times can be explained within the framework of “plate tectonics,” which is the overwhelmingly accepted unified theory of Earth sciences. This makes plate tectonics the central core discipline in geoscience research.
The Earth's lithosphere is divided into major plates and microplates that interact with each other along divergent (extensional), convergent (compressional), and transform (strike‐slip) plate boundaries. Within the past few decades, Earth sciences have made tremendous advances in our understanding of plate tectonics processes along these three types of plate boundaries.
The overarching objective of the three‐volume series Tectonic Processes: A Global View is to present an up‐to‐date compendium and valuable reference for students of Earth sciences at all levels, from advanced undergraduate and graduate to doctoral and postdoctoral researchers, as well as for educators, policymakers, and research professionals in academia and industry. The collection contains three volumes:
Volume 1:
Compressional Tectonics: Plate Convergence to Mountain Building
Volume 2:
Extensional Tectonics: Rifting and Continental Extension
Volume 3:
Strike‐Slip Tectonics: Oceanic Transform Faults to Continental Plate Boundaries
EXTENSIONAL TECTONICS
Extensional Tectonics: Rifting and Continental Extension reviews present‐day knowledge of extensional tectonic processes and explores examples from around the world. It starts with an introductory chapter outlining extensional tectonics processes from the initiation of continental rifting to oceanic basin formation. The remainder of the book is divided into three parts.
Part I: Large‐Scale Extensional Tectonics
The four chapters in Part I review large‐scale extensional terranes. Chapter 2 by Rooney et al. presents an overview of the East African Rift System. Chapter 3 by Filina and Beutel suggests a new tectonic reconstruction of the Gulf of Mexico based on geological and geophysical constraints. In Chapter 4, Busby and Putirka introduce a new concept for active obliques rifting for the extensional process from Walker Lane to the Gulf of California. And in Chapter 5, Catlos et al. investigate extensional tectonics in Western Anatolia, Turkey, as part of the Aegean Extension.
Part II: Extensional Tectonic Processes
The three chapters in Part II explore processes affecting rifting that may apply broadly to other extensional terranes. Chapter 6 by Conder explains the relationship between isostasy and seafloor spreading as a self‐sustaining process. Chapter 7 by Weise and Mahatsente explores the rigidity‐seismicity relation in the East African Rift System. To conclude, Chapter 8 by Walker et al. examines the evolution of the Mississippi Embayment and associated alkaline magmatism based on an edge‐driven convection‐based model.
Part III: Case Studies of Continental Extensional Tectonics
In Part III, four regional case studies are presented. Extensional processes in these regions can be applied to other extended terrains. Chapter 9 by Kolawole et al. explores the evolution of the Middle Shire and Nsanje rift interaction zone located along three contiguous nonvolcanic propagating rift segments. In Chapter 10, Jaramillo et al. tackle the root problem of the mid‐tertiary Cordilleran detachment faults. In Chapter 11, Merey et al. suggest a new model for the Büyük Menderes Graben in Western Turkey within the framework of the Cenozoic back‐arc extension setting. Finally, in Chapter 12, Catlos and Çemen emphasize the importance of the transfer zones of extended terranes with examples from the Aegean microplate and Western Anatolia.
ACKNOWLEDGMENTS
We appreciate the authors' contributions to this volume and acknowledge the time, effort, and diverse perspectives of a large number of insightful reviewers. This volume could not be realized without the persistent efforts of the authors and reviewers. Thank you all.
İbrahim Çemen
Department of Geological SciencesThe University of Alabama, USA
Elizabeth J. Catlos
Jackson School of Earth SciencesThe University of Texas at Austin, USA
1Processes and Perspectives in Extensional Tectonics
Elizabeth J. Catlos1 and İbrahim Çemen2
1Jackson School of Geosciences, Department of Earth and Planetary Sciences, University of Texas at Austin, Austin, Texas, USA
2Department of Geological Sciences, University of Alabama, Tuscaloosa, Alabama, USA
ABSTRACT
The study of extensional tectonics harkens to the early days of plate tectonics, as the search for mechanisms driving large continental blocks to drift apart led to advances in paleomagnetism and geochronology. Divergent plate boundaries form extensive and continuous volcanic systems covering large portions of the Earth and are fundamental to understanding how plates form. The study of extensional dynamics transects traditional geoscience disciplinary boundaries and is critical in the search for the origin and evolution of life. Extensional and normal faults are not restricted to divergent plate boundaries but are also located in regions of plate convergence and within plates. Failed rifts pose significant seismic hazards. This chapter aims to identify the importance of the study of extension and dispel common misconceptions regarding the process. Stress is a critical factor in explaining why extension occurs in the lithosphere and how magma focuses in regions of extensional tectonics.
1.1. INTRODUCTION
Divergent plate boundaries are places where pieces of Earth's lithosphere (crust + upper mantle) drift away from each other (Figures 1.1 and 1.2). They are spreading boundaries, where, in some cases, new igneous crust fills space between them or sediments deposit within new accommodation space. Divergent plate boundaries can separate ocean, continental, or transitional lithosphere and have been reviewed elsewhere (Wyllie, 1988; Sibuet & Tucholke, 2013; Acocella, 2014; Philippon & Corti, 2016; Peron‐Pinvidic et al., 2019; Acocella, 2021; Zwaan & Schreurs, 2022; Olive, 2023). Divergent plate boundaries separate plates that move in opposite directions due to an extensional stress regime. Plates can extend, stretch out, enlarge in breadth, continue in length, or expand.
Despite an apparent simple observation (two plates move apart), developments in our understanding of plate tectonics have revealed that some common generalizations about these regions are incorrect. At divergent plate boundaries, lithospheric extension is often perceived to be narrow and localized between specific plates. However, the process can also occur within plates due to diverse activity at plate boundaries and mantle dynamics. In addition to its well‐known roles at divergent boundaries, extension occurs in both transform and convergent plate boundaries and plate interiors. Misconceptions arise regarding extension because it is usually introduced during introductory geoscience courses without a complete understanding of the fundamentals of stress, strain, and rock physiochemical properties. These misconceptions include discriminating between tension versus extension and the role of magma as a passive outcome versus an active driver. Because introductory geoscience students are exposed to hazards early on at convergent and strike‐slip plate boundaries (e.g., the Himalaya, Andes, and San Andreas Fault dominate the coverage in introductory geoscience textbooks), they may not recognize the inherent nature of seismic risk associated with divergent plate boundaries. For example, failed rift systems pose some of the highest risks in intraplate tectonic settings.
Figure 1.1 Global multiresolution topography map.
Source: Adapted from Ryan et al. (2009).
Divergent plate boundaries and extensional back‐arc regions are numbered. Numbers in italics are related to subduction systems.
Source: Adapted from Coffin et al. (1998).
See Table 1.1 and Table 1.2 for information.
Figure 1.2 The cartoon cross‐section illustrates the main plate boundary types.
Source: Adapted from Kious and Tilling (2016) / U.S. Department of the Interior (USGS) / Public Domain.
Table 1.1 Extensional plate boundaries.
Adapted from Coffin et al. (1998).
No.
Plate boundary name
Plate separation
1
South Atlantic Ridge (part of Mid Atlantic Ridge)
S. America–Africa
2
North and Central Atlantic Ridge Axis (also Aegir Ridge) (part of the Mid Atlantic Ridge)
N. America–Eurasian
3
Gulf of California
N. America–Pacific
4
Eurasian Basin Spreading Ridge
N. America–Eurasia
6
Falcon Basin Fault
Maricaibo–Perija
7
Cayman Trough (Trench, Spreading Center, Rise)
N. America–Caribbean Plate
9
Reykjanes‐Nansen Ridge
N. America–Eurasia
10
Azores Spreading Center and Triple Junction
N. America–Eurasian–Africa
11
Ridge north of Taimyr, Arctic Ocean
N. America–Eurasia
12
Ridge in northeast Asia
N. America–Eurasia
13
Ridge near Okhotsk Sea
Okhotsk–N. America
14
Baikal Rift Zone
Amur–Eurasia
15
Iberia‐Africa Plate Boundary
Iberia–Africa
16
Carlsberg Ridge
Africa–Indo–Australia
17
Central Indian Ridge
Africa–Indo–Australia
18
Gulf of Aden Spreading Ridge
Africa (Somali)–Arabian
19
Red Sea Ridge Axis
Africa (Somali)–Arabian
22
Ayu Trough
Philippine Sea–Caroline
24
Sorol Trough NE of Eauripik Rise
Pacific–Caroline
25
Caroline Ridge
East–West Caroline
27
Southeast Indian Ridge
Australia–Antarctic
28
Australia‐Antarctic Spreading Ridge
Australia–Antarctic
29
East American‐Antarctic Ridge
S. America–Antarctic
30
Pacific Antarctic Spreading Ridge
Pacific–Antarctic
32
Juan Fernandez‐Antarctic Spreading Center (part of Chile Rise)
Juan Fernandez–Antarctic
36
Pacific‐Galapagos Spreading Center
Pacific–Galapagos
37
Pacific‐Cocos Spreading Center
Pacific–Cocos
38
Pacific‐Nazca Spreading Center
Pacific–Nazca
39
Juan Fernandez‐Pacific S Spreading Center
Juan Fernandez–Pacific
42
Pacific‐Rivera Ridge
Pacific–Rivera
43
Explorer Ridge
Juan de Fuca–Gorda
44
Galapagos‐Nazca Spreading Center
Galapagos–Nazca
45
Easter‐Nazca Spreading Center
Easter–Nazca
46
Juan Fernandez‐Nazca Spreading Center (part of Chile Rise)
Juan Fernandez–Nazca
47
Cocos‐Nazca Spreading Center (Cocos Ridge)
Cocos–Nazca
48
Nazca‐Antarctic Spreading Center (part of Chile Rise)
Nazca–Antarctic
Advances in our understanding of lithospheric extension have also led to significant debate about the processes involved in developing regions of extended lithosphere and new and exciting ideas about how the Earth works. This chapter aims to clarify some of the basics of extensional tectonics, emphasize the importance of the study regions of crustal extension, dispel some common misconceptions, and set the stage for the chapters that focus on extensional tectonics in this volume.
1.2. THE IMPORTANCE OF EXTENSIONAL TECTONICS
Extensional tectonics plays a vital role in understanding an array of Earth processes that range from fundamental tectonics to the evolution of life. Continental drift requires extension and the rifting apart of large land masses (Wegener, 1912; Davies, 2022). These were the first plate boundaries used as evidence for plate tectonic theory, which also led to the application and further development of the fields of paleomagnetism and radiometric dating (Hess, 1962; Vine & Matthews, 1963; Wilson, 1965; LePichon, 1968; McKenzie, 1977; Palin & Santosh, 2021; Olive, 2023). Continental breakup and basin formation are fundamental and vital processes in Earth tectonics (e.g., Pagli et al., 2015; Wang et al., 2019; Buck, 2004; Palin et al., 2020; Bonifacio et al., 2023).
The lack of acceptance of plate tectonics in the geoscience community, despite ample evidence of continental connections and shapes, paleontology, and similar rock stratigraphy and types, was in part due to the unknown mechanisms driving the process of drifting and extension (McKenzie, 1977; Frisch et al., 2011; Nyarko & Rudge, 2022; Bonifacio et al., 2023). Modern‐day plate reconstructions rely on extensional dynamics to shape and develop supercontinents. Continental extension is often restricted to occurring along narrow zones in the geological past (Dunbar & Sawyer, 1987; Seton et al., 2012). Although infrequent in the modern day, active continental extension is an important process in regulating intraplate stresses (Dalmayrac and Molnar, 1981; Rey et al., 2001; others). This volume includes a chapter on understanding reconstructions of the Gulf of Mexico (Filina and Beutel, “Geological and Geophysical Constraints Guide New Tectonic Reconstruction of the Gulf of Mexico”). The “push” from mid‐ocean ridges is invoked as a force that separates landmasses (e.g., Vink, 1982; Dunbar & Sawyer, 1987; Seton et al., 2012, 2023). Ridge push is a sliding force driven by horizontal density contrasts that develop from cooling and thickening oceanic lithosphere and is thought to contribute about 10% to plate driving forces (Hales, 1969; Solomon et al., 1980; Hager & O'Connell, 1981; Spence, 1987; Turcotte & Schubert, 2014; Mulyukova & Bercovici, 2019; Lu et al., 2021).
Divergent plate boundaries form extensive and continuous volcanic systems covering large portions of the Earth. Mid‐ocean ridges are Earth's most extensive continuous volcanic systems (Figures 1.1 and 1.2) (Perfit & Chadwick, 1998; MacDonald et al., 1991). The ridge system extends 67,338 km but is only 5–30 km wide (Macdonald, 2001; Bird, 2003). Mid‐ocean ridges are also considered the longest mountain ranges on Earth, separating plates at a rate of 10 mm/yr (Gakkel Ridge) to 170 mm/yr (East Pacific Rise) (e.g., MacDonald et al., 1991; Püthe & Gerya, 2014). Approximately 60% of Earth's surface comprises oceanic crust created at mid‐ocean ridges (Cogley, 1984; Searle, 2013), and these regions are of primary importance in modeling how new oceanic plates develop (Haymon et al., 1991; Purdy et al., 1992). The average crust production at mid‐ocean ridges is estimated at ~18 km3/year. Assuming the global ridge system was constant in length at 67,338 km, the average crust production rate is ~233–326 km3.
Oceanic crust is basaltic in composition and is further classified as mid‐ocean ridge basalt (MORB), oceanic island basalt (OIB), intraoceanic arc basalt (IOAB), island arc basalt (IAB) and continental arc basalt (CAB), depending on chemistry (see review in Xia & Li, 2019). Compositional information gleaned from basalts in MORB, OIB, IOAB, and CAB settings inform the types of tectonic processes that operate within the framework of extensional terranes. Due to their origin, MORB is Earth's most voluminous igneous phenomenon (Brooks et al., 1991; Gannoun et al., 2016). The composition of MORB is a cornerstone of discrimination diagrams used to constrain the tectonic setting of numerous regions (e.g., Floyd, 1995; Pearce, 1996; Grimes et al., 2015). The composition of minerals within basaltic rocks has also proved helpful in determining their conditions of crystallization and formation (e.g., Bryndzia et al., 1989; Ernst & Liu, 1998). Basaltic melts are generated beneath mid‐ocean ridges via decompression melting of upwelling mantle and focus beneath a ridge axis (Perfit & Chadwick, 1998; Soule, 2015). As such, basalts are used to examine processes such as mantle composition and partial melting, crust–mantle interactions, and convection (Boutilier & Keen, 1999; Gannoun et al., 2016). Differences in the morphology of fast (>80 mm/yr total spreading rate) and slow‐spreading (<55 mm/yr) mid‐ocean ridges may be due to the periodicity of magmatic heat input, which controls lithospheric rheology (e.g., Small, 1998; Dick et al., 2003; Buck et al., 2005; Püthe & Gerya, 2014). Other factors that can control mid‐ocean ridge morphology include the thermal regime, offsets in thermal perturbations, crustal thickness, and the influence of rheology on fault systems (see discussion in Püthe & Gerya, 2014). Submarine lava flows that characterize mid‐ocean ridges also influence morphology (e.g., Kennish & Lutz, 1998).
Divergent plate boundaries that separate continental lithosphere create rift zones (Figure 1.2) (e.g., Milanovsky, 1972; Kinabo et al., 2008; Zou et al., 2013). The active African Rift Valley is 3,500 km long but only 50–150 km wide (Figure 1.3) (Davies, 2008; Scoon, 2018). This volume includes two chapters dedicated to the East African Rift Valley (Weise and Mahatsente, “Rigidity–Seismicity Relation in the East African Rift System”; and Rooney et al., “The East African Rift System”). Due to the difference in the degree of contamination by the continental lithosphere, melt chemistry in regions of continental rifting differ from mid‐ocean ridges (e.g., Bailey, 1977; Wyllie, 1988), and the processes involved in generating melts in these regions are under active investigation (Neugebauer, 1983; Brune, 2016; Chiasera et al., 2021; Brune et al., 2023). Besides their origin, magma systems beneath divergent plate boundaries are studied for how they facilitate the rifting process through dike emplacement and thermal weakening (e.g., Acocella, 2014; Daniels et al., 2014; Urbani et al., 2015; Sigmundsson et al., 2015; Acocella & Trippanera, 2016) and triggering low‐angle detachment faulting (Ebinger & Casey, 2001; Bialas et al., 2010). Fundamentally, how melts are produced in the mantle, migrate, pond in the lithosphere, and are injected into the upper crust relates to constraints on the processes involved in creating volcanoes (e.g., Pagli et al., 2015).
Figure 1.3 Map of the Great African Rift Valley. Numbers on the plate boundaries are listed in Table 1.1. Arrows indicate the approximate motion of rifting. The map was developed using ArcGIS. The layers are the Global Faults Layer from ArcAtlas (Esri) (USGS), Gridded Population of the World v4 2020 (Center for International Earth Science Information Network, Columbia University, World Wide Fund for Nature), Tectonic Plates and Boundaries (Peter Bird, Hugo Ahlenius/Nordpil), and Volcanoes (Smithsonian in conjunction with the USGS, value added by TERC's earth exploration team and simplified by Roger Palmer).
Lithospheric extension also creates topographic depressions and basins. A supradetachment basin forms above a low‐angle (<30°) normal fault system that experienced large (>5 km) displacement (e.g., Friedmann & Burbank, 1995; Muñoz‐Barrera et al., 2022) and is rarely preserved as exhumation, uplift, and erosion proceeds (Jia et al., 2021). However, these are found worldwide (e.g., Basin and Range Province, Davis & Friedmann, 2005; North American Cordillera, Whitney et al., 2013; western Anatolia and the Aegean region, van Hinsbergen, 2010, Oner & Dilek, 2011; Norwegian Sea, Muñoz‐Barrera et al., 2022; South China Sea, Jia et al., 2021; Sun et al., 2022). These basins also occur throughout geological time, documented as early as the Archean (Zametzer et al., 2023). Because they are closely related to the tectonic processes that developed them, they provide critical constraints on the kinematic evolution of the extensional system (e.g., Milia & Torrente, 2015).
Volcanism at continental rifts poses hazards when intersecting large population centers, affecting the quality of air, soil, and ground and surface hydrology, which are reflected in water and food quality (Davies, 2008). Today, East Africa's rift hosts the largest urban populations and critical infrastructure, including transportation and energy and water supplies (Figure 1.3) (Hearn, 2022). Hearn (2022) identifies several of its geological hazards, including earthquakes and volcanism, landslides, ground fissuring and cavity collapse, flooding, and sedimentation problems. Significant quantities of CO2 are emitted at continental rifts, which may have influenced deep carbon fluxes and contributed to climate change (Brune et al., 2017). Lakes and rivers that develop in continental rift zones are critical for understanding climate change (e.g., Ayenew & Legesse, 2007; Olaka et al., 2010; Scholz et al., 2011). The geomorphology and active tectonics of the African rift may have controlled human evolution (Abdelsalam et al., 2004). Volatile emissions in submarine and subaerial gas releases at extensional settings have played a role in killing humans and livestock and are often overlooked as significant geohazards (Edmonds et al., 2015; Annunziatellis et al., 2003).
Fluid‐driven processes that occur at divergent plate boundaries have diverse impacts. Hydrothermal systems that develop at divergent plate boundaries also have implications for understanding climate change via degassing (Poulsen et al., 2003). At mid‐ocean ridges, hydrothermal circulation and alteration regulate seawater chemistry and global chemical fluxes (Früh‐Green et al., 2022). These regions are also important in understanding the origin of life (Holm, 1992). Geothermal processes at mid‐ocean ridges today support abundant marine life in the absence of light, so much so that an investigation found new species in every square meter of seafloor sediment (Grassle & Maciolek, 1992; Rona, 2003). Ocean gateways develop during continental breakup, influencing ocean circulation and life (Peron‐Pinvidic et al., 2019).
Ancient and modern mid‐ocean ridges are sites of valuable ore resources that appear under conditions that facilitate their development and preservation (e.g., Rona, 1984, 2003). Metalliferous muds with large amounts of Cu, Zn, Pb, Fe, Au, and Ag were first noted in the Red Sea rift (Figure 1.1 and Figure 1.3) (Laurila et al., 2015). The high concentrations are related to new oceanic crust developing in smaller, isolated deeps with high‐saline brines that favor preservation (Scholten et al., 2017). Massive sulfide deposits are in mounds along the East Pacific Rise near the Gulf of California, the Galapagos Rift, the Guaymas Basin, and the Juan de Fuca Ridge (Bischoff et al., 1983). The International Sea Bed Authority (https://www.isa.org.jm/) estimates the extensional systems at ridge, arc, and backarc spreading centers host ∼3 × 107 tons of Cu and Zn. Economic deposits can be hosted within the hydrothermal volcanic system (volcanogenic massive sulfide [VMS] deposits and seafloor massive sulfide [SMS]) or within associated sedimentary rocks (Herzig & Hannington, 1995; Humphris et al., 1995; Knight et al., 2018). Gold occurs in sulfides from the Southern Explorer Ridge and Axial Seamount (Northeast Pacific), the Trans‐Atlantic Geotraverse (TAG) hydrothermal field and Snakepit vent field (Mid‐Atlantic Ridge) (Hannington et al., 1991). Gold enrichment in these regions is associated with late‐stage, low‐temperature (<300 °C) vents (Hannington et al., 1991; Herzig & Hannington, 1995). Slower‐spreading ridges appear more enriched in gold (Knight et al., 2018). Demand for economic deposits found at mid‐ocean ridges continues to increase (Murton et al., 2019), and the International Sea Bed Authority oversees the regulation of seafloor to minimize the impact of mining on the benthic communities associated with these deposits.
Geothermal resources exist beneath regions of widespread and incipient crustal extension, even in amagmatic regions (e.g., Coolbaugh et al., 2002; Banks, 2012; Jolie et al., 2021; English et al., 2023). The Basin and Range physiographic province in the western United States is characterized by broadly distributed normal faults, thin lithosphere, long‐lived episodic magmatism, and high heat flow (Figure 1.4a,b) (e.g., Eaton, 1982). Figure 1.4b shows that the region hosts a significant fraction of geothermal resources and electricity generation capacity (Sifford & Bloomquist, 2000; Wisian & Blackwell, 2004). Extensional geothermal systems also comprise a significant portion of the geothermal installed capacity in the region (Wisian & Blackwell, 2004). Normal faults associated with extended lithosphere are critical portions of these geothermal systems and facilitate heat transfer from deep to shallow levels (e.g., Faulds et al., 2010). Two chapters in this volume focus on the extensional dynamics of the U.S. Basin and Range (Jaramillo et al., “Root Problem of Mid‐Tertiary Cordilleran Detachment Faults: Deciphering the Evolution of the Whipple Mountains Detachment Shear Zone in Southeastern California”; and Busby and Putirka, “Introduction to an Active Oblique Rift: Walker Lane to Gulf of California”).
Hot springs and geothermal activity also occur during incipient continental extension, even in areas associated with flat‐slab subduction. Back arc extension associated with flat‐slab subduction zones has been shown to lead to significant continental hydration, resulting in a reduction of lithospheric strength, mantle delamination, the development of ignimbrites, and increased lithospheric buoyancy (e.g., Scott et al., 2020; Hiett et al., 2021). This hydrothermal activity can lead to the development of significant ore deposits (e.g., Landis and Rye, 1974; Bissig et al., 2001; Newell et al., 2015).
Ore deposits are a signature of post‐collisional extensional environments. For example, Pb–Zn–Ag, Cu–Mo, and Au–Ag deposits are found in association with the development of metamorphic core complexes in the Rhodope Massif of Bulgaria (e.g., Marchev et al., 2005; Rohrmeier et al., 2013). Groves et al. (1998) document several regions with significant Au deposition that were sometimes developed during compression but facilitated and exhumed during lithospheric extension. The combination of high metamorphic temperatures, fluid infiltration, magmatism, and tectonic exhumation identifies regions of extension ideal for developing and providing access to ore minerals.
Rifted margin research has classically been related to the search for hydrocarbons (oil, gas, and coal) (e.g., Peron‐Pinvidic et al., 2019; Alves et al., 2020; Li et al., 2023). Rifts with post‐rift sag basins and rift basins with marine fill host the most known reserves of recoverable oil and gas (Lambiase & Morely, 1999). Rift basins in the Newark region (northeastern New Jersey, United States) developed during the Mesozoic and host bituminous coal that played a role in the early economic history of the United States (Robbins et al., 1988). Today, they are evaluated for their potential for CO2 sequestration (Zakharova et al., 2020).
Figure 1.4 (a) Map of the western portion of the United States, showing the location of several metamorphic core complexes.
Source: Adapted from Gébelin et al. (2011) / with permission of John Wiley & Sons.
(b) Geothermal heat flow map of the same region.
Source: Blackwell et al. (2011).
We include geothermal belts and systems.
Source: Adapted from Faulds et al. (2010).
Determining the origin and driving forces of rifting and how it evolves tectonically directly correlates to understanding its hydrocarbon potential (e.g., Rop et al., 2022). Rifts can encompass a variety of geometries as sediments within a rift system are hosted on a range of basement compositions, and architectures develop over geological time (e.g., Alves et al., 2020; Brune et al., 2023). Critical archives of environmental and climate changes are recorded within rift‐related sediments (e.g., McNeill et al., 2019; Hou et al., 2020). Deeper structural levels of highly magmatic active rifts are largely inaccessible, but ancient rifts exhumed in continental interiors can be used to understand parts of these systems and their dynamics (e.g., Oslo rift, Neumann et al., 1992). Rifts can also fail, providing additional snapshots of the extensional process (Elling et al., 2022). In this volume, we include a chapter that discuss failed rifts (Walker et al., “Edge‐Driven Convection‐Based Models for the Evolution of the Mississippi Embayment and Associated Alkaline Magmatism”). Eventually, some rift systems will interact with other plate boundaries, including convergent ones. The internal architecture of some collisional orogens is controlled by rift inheritance (e.g., Jourdon et al., 2019; Peron‐Pinvidic et al., 2019). Intraoceanic settings are one of the central regions for subduction development as convergent systems initiate at or near mid‐ocean ridges (e.g., Barth et al., 2008; Wu et al., 2023). Extinct mid‐ocean ridges may subduct, creating seismic hazards (e.g., Zhu et al., 2023) and the development of flat‐slab (low‐angle) subduction zones (Gutscher et al., 2000; Horton et al., 2022). Subduction of these features may also drive extension within the continental crust (e.g., George et al., 2022).
As discussed in this section, understanding lithospheric extension involves almost every aspect of geosciences. It will continue to be an active focus of investigation as we seek to develop new ideas about plate tectonics and search for economic resources. The following section lists a few common misconceptions about how extension operates in the lithosphere.
1.3. TERMINOLOGY AND COMMON MISCONCEPTIONS
1.3.1. Tension Is Not Extension
As the title of this subsection indicates, extension is not tension. Tension is the condition of being held in a state between two or more forces that are acting in opposition to each other. Extension is used from a kinematic perspective to represent tectonic processes under stretching in Earth's crust and lithosphere, giving rise to a range of phenomena, such as extensional tectonics and extensional basin formation (e.g., Wernicke & Burchfiel, 1982).
For example, Figure 1.3 shows the African Rift, where the Nubian plate separates from the Somalia plate, breaking up the larger African (or Nubia–Somalia) plate. In introductory courses, some students imagine a scenario where the plates separate due to imaginary forces far afield from the rift valley. Unfortunately, this common misconception may persist throughout a student's geoscience education as this plate boundary is often used as the type locality for introducing continental lithosphere extension. Students need clarification, as the arrows representing motion along the East African rift appear at odds with the sense of motion indicated by mid‐ocean ridges. However, the arrows in Figure 1.3 represent tension, not stress. Rocks respond to stress (σ), an internal force resulting from an applied load that acts along a cross‐section of a mechanical or structural component, by changing volume or form (Figure 1.5, inset). Stress is defined as force/area and has units of pressure (N/m2 or lb/in2 or Pa, pascals). Stress can be normal (perpendicular to the surface) or shear (parallel). Anderson (1905, 1951
