Essentials of Geology

Chapter 1

An Introduction to Geology

The Science of Geology

Geology, People, and the Environment

Historical Notes About Geology

            Catastrophism

            The Birth of Modern Geology

Geologic Time

The Nature of Scientific Inquiry

            Hypothesis

            Theory

            Scientific Methods

Earth’s Spheres

            Hydrosphere

            Atmosphere

            Biosphere

            Geosphere

Earth as a System

            Earth System Science

            The Earth System

The Rock Cycle: One of Earth’s Subsystems

            The Basic Cycle

            Alternative Paths

Earth’s Internal Structure

            Layers Defined by Composition

Early Evolution of Earth           

            Origin of Planet Earth

            Formation of Earth’s Layered Structure

            Layers Defined by Physical Properties

The Face of Earth

            Features of the Continents

            Features of the Ocean Basins

Dynamic Earth

            The Theory of Plate Tectonics

            Plate Boundaries

 

Box 1.1 Do Glaciers Move? An Application of the Scientific Method

 

Chapter 2

Minerals: Building Blocks of Rocks

Minerals: Building Blocks of Rocks

Elements: Building Blocks of Minerals

Why Atoms Bond

            Ionic Bonds: Electrons Transferred

            Covalent Bonds: Electrons Shared

            Other Bonds

Isotopes and Radioactive Decay

Properties of Minerals

            Primary Diagnostic Properties

            Other Properties of Minerals

Mineral Groups

The Silicates

            The Silicon—Oxygen Tetrahedron

            Other Silicate Structures

            Joining Silicate Structures

Common Silicate Minerals

            The Light Silicates

            The Dark Silicates

Important Nonsilicate Minerals

Mineral Resources

 

Box 2.1 Asbestos: What Are the Risks?

 

Chapter 3

Igneous Rocks

Magma: The Parent Material of Igneous Rock

            The Nature of Magma

            From Magma to Crystalline Rock

            Igneous Textures

            Factors Affecting Crystal Size

            Types of Igneous Textures

Igneous Compositions

            Granitic versus Basaltic Compositions

            Other Compositional Groups

            Silica Content as an Indicator of Composition

Naming Igneous Rocks

            Felsic (Granitic) Igneous Rocks

            Intermediate (Andesitic) Igneous Rocks

            Mafic (Basaltic) Igneous Rocks

            Pyroclastic Rocks

Origin of Magma

            Generating Magma from Solid Rock

How Magmas Evolve

            Bowen’s Reaction Series and the Composition of Igneous Rocks

            Assimilation and Magma Mixing

            Partial Melting and Magma Formation

Mineral Resources and Igneous Processes

 

Box 3.1 A Closer Look at Bowen’s Reaction Series

Chapter 4

Volcanoes and Other Igneous Activity

The Nature of Volcanic Eruptions

            Factors Affecting Viscosity

            Importance of Dissolved Gases

Materials Extruded During an Eruption

            Lava Flows

            Gases

            Pyroclastic Materials

Volcanic Structures and Eruptive Styles

            Anatomy of a Volcano

            Shield Volcanoes

            Cinder Cones

            Composite Cones

Living in the Shadow of a Composite Cone

            Eruption of Vesuvius a.d. 79

            Nuée Ardente: A Deadly Pyroclastic Flow

            Lahars: Mudflows on Active and Inactive Cones

Other Volcanic Landforms

            Calderas

            Fissure Eruptions and Basalt Plateaus

            Volcanic Pipes and Necks

Intrusive Igneous Activity

            Nature of Plutons

            Diles

            Sills and Laccoliths

            Batholiths

Plate Tectonics and Igneous Activity

            Igneous Activity at Convergent Plate Boundaries

            Igneous Activity at Divergent Plate Boundaries

            Intraplate Igneous Activity

 

Box 4.1 Anatomy of an Eruption

Box 4.2 Can Volcanoes Change Earth’s Climate?

 

Chapter 5

Weathering and Soils

Earth’s External Processes

Weathering

Mechanical Weathering

            Frost Wedging

            Unloading

            Biological Activity

Chemical Weathering

            Water and Carbonic Acid

            How Granite Weathers

            Weathering of Silicate Minerals

            Spheroidal Weathering

Rates of Weathering

            Rock Characteristics

            Climate

            Differential Weathering

Soil

            An Interface in the Earth System

            What Is Soil?

Controls of Soil Formation

            Parent Material

            Time

            Climate

            Plants and Animals

            Topography

The Soil Profile

Soil Erosion

            How Soil Is Eroded

Classifying Soils

            Rates of Erosion

            Sedimentation and Chemical Pollution

Weathering: The Cause of Ore Deposits

            Bauxite

            Other Deposits

 

Box 5.1 Clearing the Tropical Rain ForestThe Impact on Its Soils

 

Chapter 6

Sedimentary Rocks

What Is a Sedimentary Rock?

Turning Sediment into Sedimentary Rock: Diagenesis and Lithification

Types of Sedimentary Rocks

Detrital Sedimentary Rocks

            Shale

            Sandstone

            Conglomerate and Breccia

Chemical Sedimentary Rocks

            Limestone

            Dolostone

            Chert

            Evaporites

            Coal

Classification of Sedimentary Rocks

Sedimentary Rocks Represent Past Environments

Sedimentary Structures

Nonmetallic Mineral Resources from Sedimentary Rocks

Energy Resources from Sedimentary Rocks

            Coal

            Oil and Natural Gas

 

Box 6.1: The Carbon Cycle and Sedimentary Rocks

 

Chapter 7

Metamorphic Rocks

Metamorphism

Agents of Metamorphism

            Heat as a Metamorphic Agent

            Pressure and Differential Stress

            Chemically Active Fluids

Metamorphic Textures

            Foliation

            Foliated Textures

            Other Metamorphic Textures

Common Metamorphic Rocks

            Foliated Rocks

            Nonfoliated Rocks

Metamorphic Environments

            Contact or Thermal Metamorphism

            Hydrothermal Metamorphism

            Regional Metamorphism

            Other Metamorphic Environments

Metamorphic Zones

            Textural Variations

            Index Minerals and Metamorphic Grade

 

Chapter 8

Mass Wasting: The Work of Gravity

A Landslide Disaster in Peru

Mass Wasting and Landform Development

            The Role of Mass Wasting

            Slopes Change Through Time

Controls and Triggers of Mass Wasting

            The Role of Water

            Oversteepened Slopes

            Removal of Vegetation

            Earthquakes as Triggers

            Landslides Without Triggers?

Classification of Mass-Wasting Processes

            Type of Material

            Type of Motion

            Rate of Movement

Slump

Rockslide

Debris Flow

            Debris Flows in Semiarid Regions

Lahars

Earthflow

Slow Movements

            Creep

            Solifluction

 

Box 8.1: Debris Flows on Alluvial Fans: A Case Study from Venezuela

Box 8.2: The Sensitive Permafrost Landscape

 

Chapter 9

Running Water

Earth as a System: The Hydrologic Cycle

Running Water

            Drainage Basins

            River Systems

Streamflow

            Gradient and Channel Characteristics

            Discharge

            Changes from Upstream to Downstream

The Work of Running Water

            Erosion

            Transportation

            Deposition

Stream Channels

            Bedrock Channels

            Alluvial Channels

Base Level and Stream Erosion

Shaping Stream Valleys

            Valley Deepening

            Valley Widening

            Changing Base Level and Incised Meanders

Depositional Landforms

            Deltas

            Natural Levees

            Alluvial Fans

Drainage Patterns

Floods and Flood Control

            Causes and Types of Floods

            Flood Control

 

Box 9.1: Coastal Wetlands Are Vanishing on the Mississippi Delta

 

Chapter 10

Groundwater

Importance of Underground Water

Distribution of Underground Water

The Water Table

            Variations in the Water Table

            Interaction Between Groundwater and Streams

Factors Influencing the Storage and Movement of Groundwater

            Porosity

            Permeability, Aquitards, and Aquifers

How Groundwater Moves

Springs

Wells

Artesian Wells

Environmental Problems Associated with Groundwater

            Treating Groundwater as a Nonrenewable Resource

            Land Subsidence Caused by Groundwater Withdrawal

            Groundwater Contamination

Hot Springs and Geysers

Geothermal Energy

The Geologic Work of Groundwater

            Caverns

            Karst Topography

 

Box 10.1 Measuring Groundwater Movement

Box 10.2: The Case of the Disappearing Lake

 

Chapter 11

Glaciers and Glaciation

Glaciers: A Part of Two Basic Cycles

            Valley (Alpine) Glaciers

            Other Types of Glaciers

How Glaciers Move

            Rates of Glacial Movement

            Budget of a Glacier

Glacial Erosion

Landforms Created by Glacial Erosion

            Glaciated Valleys

            Arêtes and Horns

            Roches Moutonnées

Glacial Deposits

            Types of Glacial Drift

            Moraines, Outwash Plains, and Kettles

            Drumlins, Eskers, and Kames

Glaciers of the Ice Age

Some Indirect Effects of Ice Age Glaciers

Causes of Glaciation

            Plate Tectonics

            Variations in Earth’s Orbit

            Other Factors

 

Box 11.1 The Collapse of Antarctic Ice Shelves

Box 11.2 Glacial IceA Storehouse of Climate Data

 

Chapter 12

Deserts and Wind

Distribution and Causes of Dry Lands

            Low-Latitude Deserts

            Middle-Latitude Deserts

Geologic Processes in Arid Climates

            Weathering

            The Role of Water

Basin and Range: The Evolution of a Desert Mountainous Landscape

Transportation of Sediment by Wind

            Bed Load

            Suspended Load

Wind Erosion

            Deflation, Blowouts, and Desert Pavement

            Wind Abrasion

Wind Deposits

            Sand Deposits

            Types of Sand Dunes

            Loess (Silt) Deposits

 

Box 12.1 The Disappearing Aral Sea

Box 12.2 Dust BowlSoil Erosion in the Great Plains

 

Chapter 13

Shorelines

The Shoreline: A Dynamic Interface

The Coastal Zone

Waves

            Wave Characteristics

            Circular Orbital Motion

            Waves in the Surf Zone

Wave Erosion

Sand Movement on the Beach

            Movement Perpendicular to the Shoreline

            Wave Refraction

            Beach Drift and Longshore Currents

Shoreline Features

            Erosional Features

            Depositional Features

            The Evolving Shore

Stabilizing the Shore

            Hard Stabilization

            Alternatives to Hard Stabilization

            Erosion Problems Along U.S. Coasts

Coastal Classification

            Emergent Coasts

            Submergent Coasts

Tides

            Causes of Tides

            Monthly Tidal Cycle

            Tidal Currents

 

Box 13.1 The Move of the CenturyRelocating the Cape Hatteras Lighthouse

Box 13.2 Coastal Vulnerability to Sea-Level Rise

 

Chapter 14

Earthquakes and Earth’s Interior

What Is an Earthquake?

            Earthquakes and Faults

            Discovering the Cause of Earthquakes

            Foreshocks and Aftershocks

San Andreas Fault: An Active Earthquake Zone

Seismology: The Study of Earthquake Waves

Locating an Earthquake

Measuring the Size of Earthquakes

            Intensity Scales

            Magnitude Scales

Destruction from Earthquakes

            Destruction from Seismic Vibrations

            Tsunami

            Landslides and Ground Subsidence

            Fire

Can Earthquakes Be Predicted?

            Short-Range Predictions

            Long-Range Forecasts

Earthquake’s and Earth’s Interior

            Layers Defined by Composition

            Layers Defined by Physical Properties

            Discovering Earth’s Major Layers

            Discovering Earth’s Composition

 

Box 14.1 Damaging Earthquakes East of the Rockies

 

 

Chapter 15

Plate Tectonics: A Scientific Theory Unfolds

Continental Drift: An Idea Before Its Time

            Evidence: The Continental Jigsaw Puzzle

            Evidence: Fossils Match Across the Seas

            Evidence: Rock Types and Structures Match

            Evidence: Ancient Climates

The Great Debate

Plate Tectonics: The New Paradigm

            Earth’s Major Plates

            Plate Boundaries

Divergent Boundaries

            Oceanic Ridges and Seafloor Spreading

            Continental Rifting

Convergent Boundaries

            Oceanic—Continental Convergence

            Oceanic-Oceanic Convergence

            Continental—Continental Convergence

Transform Fault Boundaries

Testing the Plate Tectonics Model

            Evidence: Ocean Drilling

            Evidence: Hot Spots

            Evidence: Paleomagnetism

Measuring Plate Motion

What Drives Plate Motion?

            Forces that Drive Plate Motion

            Models of Plate-Mantle Convection

Plate Tectonics into the Future

 

Box 15.1 The Breakup of Pangaea

 

Chapter 16

Origin and Evolution of the Ocean Floor

An Emerging Picture of the Ocean Floor

            Mapping the Seafloor

            Viewing the Ocean Floor from Space

            Provinces of the Ocean Floor

Continental Margins

            Passive Continental Margins

            Active Continental Margins

Features of Deep-Ocean Basins

            Deep-Ocean Trenches

            Abyssal Plains

            Seamounts, Guyots, and Oceanic Plateaus

Anatomy of the Oceanic Ridge

Origin of Oceanic Lithosphere

            Seafloor Spreading

            Why Are Oceanic Ridges Elevated?

            Spreading Rates and Ridge Topography

The Structure of Oceanic Crust

            Formation of Oceanic Crust

            Interactions Between Seawater and Oceanic Crust

Continental Rifting: The Birth of a New Ocean Basin

            Evolution of an Ocean Basin

Destruction of Oceanic Lithosphere

            Why Oceanic Lithosphere Subducts

            Subducting Plates: The Demise of an Ocean Basin

Opening and Closing Ocean Basins: The Supercontinent Cycle

            Before Pangaea

 

Box 16.1 Explaining Coral AtollsDarwin’s Hypothesis

 

Chapter 17

Crustal Deformation and Mountain Building

Rock Deformation

            Temperature and Confining Pressure

            Rock Type

            Time

Folds

            Types of Folds

            Domes and Basins

Faults

            Dip-Slip Faults

            Strike-Slip Faults

Joints

Mountain Building at Subduction Zones

            Island Arcs

Mountain Building Along Andean-Type Margins

Mountain Building

Collisional Mountain Ranges

            Terranes and Mountain Building

            Continental Collisions

Fault-Block Mountains

Vertical Movements of the Crust

            Isostasy

            How High Is Too High?

Box 17.1 The San Andreas Fault System

 

Chapter 18

Geologic Time

Geology Needs a Time Scale

Relative DatingKey Principles

            Law of Superposition

            Principle of Original Horizontality

            Principle of Cross-Cutting Relationships

            Inclusions

            Unconformities

            Using Relative Dating Principles

Correlation of Rock Layers

Fossils: Evidence of Past Life

            Types of Fossils

            Conditions Favoring Preservation

            Fossils and Correlation

Dating with Radioactivity

            Reviewing Basic Atomic Structure

            Radioactivity

            Half-Life

            Radiometric Dating

            Dating with Carbon-14

            Importance of Radiometric Dating

The Geologic Time Scale

            Structure of the Time Scale

            Precambrian Time

Difficulties in Dating the Geologic Time Scale

 

Box 18.1 Radon

Box 18.2 Using Tree Rings to Date and Study the Recent Past

 

Chapter 19

Earth History: A Brief Summary

Early Evolution of Earth

            Earth’s Primitive Atmosphere

            Earth’s Atmosphere Evolves

Precambrian Time: Vast and Enigmatic

            Precambrian History

            Precambrian Fossils

Paleozoic Era: Life Explodes

            Paleozoic History

            Early Paleozoic Life

            Late Paleozoic Life

Mesozoic Era: Age of the Dinosaurs

            Mesozoic History

            Mesozoic Life

Cenozoic Era: Age of Mammals

            Cenozoic North America

            Cenozoic Life

Box 19.1 Demise of the Dinosaurs