xv
xv
• Anatomy of the Oceanic Ridge 402
• Oceanic Ridges and Seafloor Spreading 403
Seafloor Spreading 403
Why Are Oceanic Ridges Elevated? 403
Spreading Rates and Ridge Topography 404
The Nature of Oceanic Crust 405
How Does Oceanic Crust Form? 405
Interactions between Seawater and Oceanic Crust 406
Continental Rifting: The Birth of a New Ocean
Basin 407
Evolution of an Ocean Basin 407
Destruction of Oceanic Lithosphere 409
Why Oceanic Lithosphere Subducts 409
Subducting Plates: The Demise of an Ocean Basin 410
THE CHAPTER IN REVIEW 412 KEY TERMS 412
GIVE IT SOME THOUGHT 413 COMPANION
WEBSITE 415
17 Crustal Deformation
and Mountain Building 414
• Crustal Deformation 416
Elastic, Brittle, and Ductile Deformation 416
Factors that Affect Rock Strength 416
• Structures Formed by Ductile Deformation 418
Folds 418
• Structures Formed by Brittle Deformation 421
Faults 421
Dip-Slip Faults 422
Strike-Slip Faults 423
Joints 424
Mountain Building 425
Mountain Building at Subduction Zones 425
Volcanic Island Arcs 426
Mountain Building along Andean-type Margins 426
• Collisional Mountain Belts 427
Terranes and Mountain Building 427
Continental Collisions 428
The Himalayas 429
The Appalachians 430
Fault-Block Mountains 431
Basin and Range Province 432
Vertical Movements of the Crust 432
Isostasy 432
THE CHAPTER IN REVIEW 435 KEY TERMS 435
GIVE IT SOME THOUGHT 435 COMPANION
WEBSITE 435
18 Geologic Time 436
Geology Needs a Time Scale 438
• Relative Dating—Key Principles 438
Law of Superposition 440
Principle of Original Horizontality 440
Principle of Cross-Cutting Relationships 441
Inclusions 441
Unconformities 442
Using Relative Dating Principles 443
Correlation of Rock Layers 444
Fossils: Evidence of Past Life 445
Types of Fossils 445
Conditions Favoring Preservation 448
Fossils and Correlation 448
• Dating with Radioactivity 449
Reviewing Basic Atomic Structure 449
Radioactivity 450
Half-Life 451
Radiometric Dating 452
Dating with Carbon-14 452
Importance of Radiometric Dating 453
Using Tree Rings to Date and Study the Recent Past 454
• The Geologic Time Scale 455
Structure of the Time Scale 455
Precambrian Time 455
Terminology and the Geologic Time Scale 455
Difficulties in Dating the Geologic
Time Scale 457
THE CHAPTER IN REVIEW 459
KEY TERMS 459 GIVE IT SOME THOUGHT 459
COMPANION WEBSITE 459
19 Earth’s Evolution
through Geologic Time 460
Is Earth Unique? 462
The Right Planet 462
The Right Location 463
The Right Time 463
Birth of a Planet 465
From Planetesimals to Protoplanets 465
Earth’ s Early Evolution 465
Origin of the Atmosphere and Oceans 467
Earth’ s Primitive Atmosphere 467
Oxygen in the Atmosphere 467
Evolution of the Oceans 468
GEODe
ESSENTIALS
OF GEOLOGY
• Indicates sections with a corresponding
GEODe activity on mygeoscienceplace.com.
xv
• Anatomy of the Oceanic Ridge 402
• Oceanic Ridges and Seafloor Spreading 403
Seafloor Spreading 403
Why Are Oceanic Ridges Elevated? 403
Spreading Rates and Ridge Topography 404
The Nature of Oceanic Crust 405
How Does Oceanic Crust Form? 405
Interactions between Seawater and Oceanic Crust 406
Continental Rifting: The Birth of a New Ocean
Basin 407
Evolution of an Ocean Basin 407
Destruction of Oceanic Lithosphere 409
Why Oceanic Lithosphere Subducts 409
Subducting Plates: The Demise of an Ocean Basin 410
THE CHAPTER IN REVIEW 412 KEY TERMS 412
GIVE IT SOME THOUGHT 413 COMPANION
WEBSITE 415
17 Crustal Deformation
and Mountain Building 414
• Crustal Deformation 416
Elastic, Brittle, and Ductile Deformation 416
Factors that Affect Rock Strength 416
• Structures Formed by Ductile Deformation 418
Folds 418
• Structures Formed by Brittle Deformation 421
Faults 421
Dip-Slip Faults 422
Strike-Slip Faults 423
Joints 424
Mountain Building 425
Mountain Building at Subduction Zones 425
Volcanic Island Arcs 426
Mountain Building along Andean-type Margins 426
• Collisional Mountain Belts 427
Terranes and Mountain Building 427
Continental Collisions 428
The Himalayas 429
The Appalachians 430
Fault-Block Mountains 431
Basin and Range Province 432
Vertical Movements of the Crust 432
Isostasy 432
THE CHAPTER IN REVIEW 435 KEY TERMS 435
GIVE IT SOME THOUGHT 435 COMPANION
WEBSITE 435
18 Geologic Time 436
Geology Needs a Time Scale 438
• Relative Dating—Key Principles 438
Law of Superposition 440
Principle of Original Horizontality 440
Principle of Cross-Cutting Relationships 441
Inclusions 441
Unconformities 442
Using Relative Dating Principles 443
Correlation of Rock Layers 444
Fossils: Evidence of Past Life 445
Types of Fossils 445
Conditions Favoring Preservation 448
Fossils and Correlation 448
• Dating with Radioactivity 449
Reviewing Basic Atomic Structure 449
Radioactivity 450
Half-Life 451
Radiometric Dating 452
Dating with Carbon-14 452
Importance of Radiometric Dating 453
Using Tree Rings to Date and Study the Recent Past 454
• The Geologic Time Scale 455
Structure of the Time Scale 455
Precambrian Time 455
Terminology and the Geologic Time Scale 455
Difficulties in Dating the Geologic
Time Scale 457
THE CHAPTER IN REVIEW 459
KEY TERMS 459 GIVE IT SOME THOUGHT 459
COMPANION WEBSITE 459
19 Earth’s Evolution
through Geologic Time 460
Is Earth Unique? 462
The Right Planet 462
The Right Location 463
The Right Time 463
Birth of a Planet 465
From Planetesimals to Protoplanets 465
Earth’ s Early Evolution 465
Origin of the Atmosphere and Oceans 467
Earth’ s Primitive Atmosphere 467
Oxygen in the Atmosphere 467
Evolution of the Oceans 468
GEODe
ESSENTIALS
OF GEOLOGY
• Indicates sections with a corresponding
GEODe activity on mygeoscienceplace.com.