Geology For Dummies

Introduction 1 About This Book 1 Foolish Assumptions 2 Icons Used in This Book 2 Beyond the Book 3 Where to Go from Here 3 Part 1: Studying The Earth 5 Chapter 1: Rocks for Jocks (and Everybody Else) 7 Finding Your Inner Scientist 8 Making observations every day 8 Jumping to conclusions 8 Focusing on Rock Formation and Transformation 8 Understanding how rocks form 9 Tumbling through the rock cycle 9 Mapping Continental Movements 10 Unifying geology with plate tectonics theory 10 Debating a mechanism for plate movements 11 Moving Rocks around on Earth’s Surface 11 Interpreting a Long History of Life on Earth 12 Using relative versus absolute dating 12 Witnessing evolution in the fossil record 13 Chapter 2: Observing Earth through a Scientific Lens 15 Realizing That Science Is Not Just for Scientists 15 Using a Methodical Approach: The Scientific Method 16 Sensing something new 17 I have a hypothesis! 18 Testing your hypothesis: Experiments 18 Crunching the numbers 19 Interpreting results 21 Sharing the findings 21 Building New Knowledge: A Scientific Theory 21 It’s never “just a theory” 22 Scientific theory versus scientific law 22 The road to paradigms 23 Speaking in Tongues: Why Geologists Seem to Speak a Separate Language 23 Lamination vs foliation: Similar outcomes from different processes 24 Gabbro vs basalt: Different outcomes from similar processes 24 Chapter 3: From Here to Eternity: The Past, Present, and Future of Geologic Thought 27 Catastrophe Strikes Again and Again 28 Early Thoughts on the Origin of Rocks 28 Developing Modern Geologic Understanding 29 Reading the rock layers: Steno’s stratigraphy 29 These things take time! Hutton’s hypothesis 30 What has been will be: Lyell’s principles 31 Uniformi-what? Understanding the Earth through Uniformitarianism 32 Pulling It All Together: The Theory of Plate Tectonics 32 Forging Ahead into New Frontiers 33 Asking how, where, and why: Mountain building and plate boundaries 33 Mysteries of the past: Snowball earth, first life, and mass extinctions 34 Predicting the future: Earthquakes and climate change 35 Out of this world: Planetary geology and the search for life 37 Chapter 4: Home Sweet Home: Planet Earth 39 Earth’s Spheres 39 Examining Earth’s Geosphere 41 Defining Earth’s layers 41 Examining each layer 43 Part 2: Elements, Minerals, And Rocks 49 Chapter 5: It’s Elemental, My Dear: A Very Basic Chemistry of Elements and Compounds 51 The Smallest Matter: Atoms and Atomic Structure 52 Getting to know the periodic table 53 Interpreting isotopes 56 Charging particles: Ions 56 Chemically Bonding 57 Donating electrons (ionic bonds) 57 Sharing electrons (covalent bonds) 57 Migrating electrons (metallic bonds) 58 Formulating Compounds 60 Chapter 6: Minerals: The Building Blocks of Rocks 61 Meeting Mineral Requirements 62 Making Crystals 62 Identifying Minerals Using Physical Characteristics 63 Observing transparency, color, luster, and streak 63 Measuring mineral strength 64 If it tastes like salt, it must be halite: Noting unique mineral properties 68 Measuring properties in the lab 69 Realizing Most Rocks Are Built from Silicate Minerals 70 Finding silicates in many shapes 71 Grouping silicate minerals 74 Remembering the Nonsilicate Minerals 74 Carbonates 74 Sulfides and sulfates 75 Oxides 75 Native elements 76 Evaporites 76 Gemstones 77 Chapter 7: Recognizing Rocks: Igneous, Sedimentary, and Metamorphic Types 79 Mama Magma: Birthing Igneous Rocks 80 Remembering how magma is made 80 Classifying melt composition 81 Reacting in sequence: Bowen’s reaction series 81 Evolving magmas 83 Crystallizing one way or another: Igneous rocks 84 Classifying igneous rocks 85 Studying volcanic structures 89 Looking below the surface 92 Merging Many Single Grains of Sand: Sedimentary Rocks 94 Weathering rocks into sediments 95 Changing from sediment into rock 98 Sizing up the grains: Classifying sedimentary rocks 99 Searching for sedimentary basins 102 Telling stories of the past: Sedimentary structures 103 Stuck between a Rock and a Hard Place: Metamorphic Rocks 106 Turning up the heat and pressure: Metamorphism 106 Grading metamorphism with index minerals 107 Between the mineral sheets: Foliation, or maybe not 108 Categorizing metamorphic rocks 110 Tumbling through the Rock Cycle: How Rocks Change from One Type to Another 112 Part 3: One Theory To Explain It All: Plate Tectonics 115 Chapter 8: Adding Up the Evidence for Plate Tectonics 117 Drifting Apart: Wegener’s Idea of Continental Drift 118 Continental puzzle solving 118 Fossil matching 119 Stratigraphic stories 120 Icy cold climates of long ago 122 Meeting at the equator 123 Searching for a mechanism 123 Coming Together: How Technology Sheds Light on Plate Tectonics 124 Mapping the seafloor 124 Flip-flopping magnetic poles: Paleomagnetism and seafloor spreading 125 Measuring plate movements 127 Unifying the theory 127 Chapter 9: When Crustal Plates Meet, It’s All Relative 129 Density Is Key 130 Two of a Kind: Continental and Oceanic Crust 131 Dark and dense: Oceanic crust 131 Thick and fluffy: Continental crust 131 Understanding Why Density Matters: Isostasy 132 Defining Plate Boundaries by Their Relative Motion 133 Driving apart: Divergent plate boundaries 134 Crashing together: Convergent plate boundaries 136 Slip-sliding along: Transform plate boundaries 139 Shaping Topography with Plate Movements 141 Deforming the crust at plate boundaries 141 Compressing rocks into folds 142 Faulting in response to stress 144 Building mountains 146 Chapter 10: Who’s Driving This Thing? Mantle Convection and Plate Movement 149 Running in Circles: Models of Mantle Convection 150 Mantle plumes: Just like the lava in your lamp 152 The slab-pull and ridge-push models 152 Using Convection to Explain Magma, Volcanoes, and Underwater Mountains 153 Plate friction: Melting rock beneath the earth’s crust 154 Creating volcanic arcs and hotspots 154 Birthing new seafloor at mid-ocean ridges 158 Shake, Rattle, and Roll: How Plate Movements Cause Earthquakes 158 Responding elastically 159 Sending waves through the earth 160 Measuring magnitude 160 Part 4: Superficially Speaking: About Surface Processes 163 Chapter 11: Gravity Takes Its Toll: Mass Wasting 165 Holding Steady or Falling Down: Friction versus Gravity 166 Focusing on the Materials Involved 167 Loose materials: Resting at the angle of repose 167 Bedrock: Losing its stability 168 Triggering Mass Movements 168 Adding water to the mix 168 Changing the slope angle 169 Shaking things up: Earthquakes 170 Removing vegetation 170 Moving Massive Amounts of Earth, Quickly 171 Falls 171 Slides and slumps 171 Flows 172 A More Subtle Approach: Creep and Soil Flow (Solifluction) 173 Chapter 12: Water: Above and Below Ground 175 Hydrologic Cycling 176 Driving the cycle with evaporation 176 Traveling across a continent 177 Streams: Moving Sediments toward the Ocean 178 Draining the basin 178 Two types of flow 179 Measuring stream characteristics 180 Carrying a heavy load 180 Measuring what is transported 181 Eroding a Stream Channel to Base Level 182 Seeking Equilibrium after Changes in Base Level 183 Leaving Their Mark: How Streams Create Landforms 184 Draining the basin 184 Meandering along 185 Depositing sediments along the way 187 Reaching the sea 187 Flowing beneath Your Feet: Groundwater 188 Infiltrating tiny spaces underground 188 Measuring porosity and permeability 189 Setting the water table 189 Springing from rocks 190 That sinking feeling: Karst, caves, and sinkholes 192 Chapter 13: Flowing Slowly toward the Sea: Glaciers 195 Identifying Three Types of Glaciers 196 Understanding Ice as a Geologic Force 196 Transforming snow into ice 197 Balancing the glacial budget 197 Flowing solidly down the mountain 198 Eroding at a Snail’s Pace: Landforms Created by Glacial Erosion 199 Plucking and abrading along the way 200 Creating their own valleys 200 Speaking French: Cirques, arêtes, et roche moutonnées 201 Leaving It All Behind: Glacial Deposits 203 Depositing the till 203 Plains, trains, eskers, and kames 204 Behaving erratically: Large boulders in odd places 206 Where Have All the Glaciers Gone? 206 Filling the erosional gaps 206 Cycling through ice ages 207 Rebounding isostatically 209 Chapter 14: Blowing in the Wind: Moving Sediments without Water 211 Lacking Water: Arid Regions of the Earth 212 Transporting Particles by Air 212 Skipping right along: Bed load and saltation 213 Suspending particles in air 214 Deflating and Abrading: Features of Wind Erosion 214 Removing sediments 215 Scratching the surface 215 Just Add Wind: Dunes and Other Depositional Wind Features 216 Migrating piles of sand: Dunes 217 Shaping sand 218 Laying down layers of loess 219 Paving the Desert: Deposition or Erosion? 221 Chapter 15: Catch a Wave: The Evolution of Shorelines 223 Breaking Free: Waves and Wave Motion 223 Dissecting wave anatomy 223 Starting to roll 224 Going with the flow: Currents and tides 226 Shaping Shorelines 228 Carving cliffs and other features 228 Budgeting to build sandbars 228 Categorizing Coastlines 230 Part 5: Long, Long Ago In This Galaxy Right Here 233 Chapter 16: Getting a Grip on Geologic Time 235 The Layer Cake of Time: Stratigraphy and Relative Dating 236 Speaking relatively 236 Sorting out the strata 236 Putting rock layers in the right order 237 Losing time in the layers 238 Show Me the Numbers: Methods of Absolute Dating 240 Measuring radioactive decay 241 Common radioactive isotopes for geological dating 244 Other exacting methods of geological dating 245 Relatively Absolute: Combining Methods for the Best Results 248 Eons, Eras, and Epochs (Oh My!): Structuring the Geologic Timescale 249 Chapter 17: A Record of Life in the Rocks 253 Explaining Change, Not Origins: The Theory of Evolution 254 The Evolution of a Theory 254 Acquiring traits doesn’t do it 254 Naturally, selecting for survival 255 Mendel’s peas please 255 Genetic nuts and bolts 256 Spontaneously mutating genes 256 Speciating right and left 257 Putting Evolution to the Test 258 Against All Odds: The Fossilization of Lifeforms 259 Bones, teeth, and shell: Body fossils 259 Just passing through: Trace fossils 260 Correcting for Bias in the Fossil Record 261 Hypothesizing Relationships: Cladistics 262 Chapter 18: Time before Time Began: The Precambrian 265 In the Beginning Earth’s Creation from a Nebulous Cloud 266 Addressing Archean Rocks 267 Creating continents 267 Revving up the rock cycle 267 Feeling hot, hot, hot: Evidence for extreme temperatures 269 Originating with Orogens: Supercontinents of the Proterozoic Eon 270 Single Cells, Algal Mats, and the Early Atmosphere 271 Hunting early prokaryotes and eukaryotes 271 You know it as pond scum: Cyanobacteria 272 Waiting to inhale: The formation of Earth’s atmosphere 275 Questioning the Earliest Complex Life: The Ediacaran Fauna 278 Chapter 19: Teeming with Life: The Paleozoic Era 281 Exploding with Life: The Cambrian Period 282 Toughen up! Developing shells 282 Ruling arthropods of the seafloor: Trilobites 283 Building Reefs All Over the Place 284 Swimming freely: Ammonoids and nautiloids 285 Exploring freshwater: Eurypterids 287 Spinal Tapping: Animals with Backbones 287 Fish evolve body armor, teeth, and legs? 287 Venturing onto land: Early amphibians 290 Adapting to life on land: The reptiles 290 Planting Roots: Early Plant Evolution 291 Tracking the Geologic Events of the Paleozoic 293 Constructing continents 293 Reading the rocks: Transgressions and regressions 294 Fossilizing carbon fuels 297 Pangaea, the most super of supercontinents 297 Chapter 20: Mesozoic World: When Dinosaurs Dominated 299 Driving Pangaea Apart at the Seams 300 One continent becomes many 300 Influencing global climate 301 Creating the mountains of North America 302 Repopulating the Seas after Extinction 303 The Symbiosis of Flowers 304 Recognizing All the Mesozoic Reptiles 306 Flocking together 308 Climbing the Dinosaur Family Tree 308 Branching out: Ornithischia and Saurischia 308 Horned faces and armor: Ornithischian dinosaurs 309 Long necks and meat eaters: Saurischian dinosaurs 312 Flocking Together: The Evolutionary Road to Birds 313 Laying the Groundwork for Later Dominance: Early Mammal Evolution 314 Chapter 21: The Cenozoic Era: Mammals Take Over 315 Putting Continents in Their Proper (Okay, Current) Places 316 Creating modern geography 316 Consuming the Farallon Plate 317 Carving the Grand Canyon with uplift 319 Icing over northern continents 320 Entering the Age of Mammals 320 Regulating body temperature 322 Filling every niche 323 Living Large: Massive Mammals Then and Now 323 Nosing around elephant evolution 324 Returning to the sea: Whales 325 Larger than life: Giant mammals of the ice ages 326 Right Here, Right Now: The Reign of Homo Sapiens 327 Arguing for the Anthropocene 329 Altering the climate 329 Shaping the landscape 330 Leaving evidence in the rock record 332 Chapter 22: And Then There Were None: Major Extinction Events in Earth’s History 333 Explaining Extinctions 334 Heads up! Astronomical impacts 334 Lava, lava everywhere: Volcanic eruptions and flood basalts 335 Shifting sea levels 337 Changing climate 337 End Times, at Least Five Times 337 Cooling tropical waters 338 Reducing carbon dioxide levels 338 The Great Dying 339 Paving the way for dinosaurs 340 Demolishing dinosaurs: The K/T boundary 340 Modern Extinctions and Biodiversity 342 Hunting the megafauna 342 Reducing biodiversity 343 Part 6: The Part of Tens 345 Chapter 23: Ten Ways You Use Geologic Resources Every Day 347 Burning Fossil Fuels 347 Playing with Plastics 348 Gathering Gemstones 348 Drinking Water 349 Creating Concrete 349 Paving Roads 350 Accessing Geothermal Heat 350 Fertilizing with Phosphate 350 Constructing Computers 351 Building with Beautiful Stone 351 Chapter 24: Ten Geologic Hazards 353 Changing Course: River Flooding 353 Caving In: Sinkholes 354 Sliding Down: Landslides 354 Shaking Things Up: Earthquakes 355 Washing Away Coastal Towns: Tsunamis 355 Destroying Farmland and Coastal Bluffs: Erosion 356 Fiery Explosions of Molten Rock: Volcanic Eruptions 356 Melting Ice with Fire: Jokulhlaups 357 Flowing Rivers of Mud: Lahars 357 Watching the Poles: Geomagnetism 358 Index 359