Geology For Dummies

Alecia M. Spooner has been teaching at the college level for more than 15 years. She currently teaches at Seattle Central College, where she is Professor of Earth and Environmental Sciences. Alecia teaches earth science courses that are accessible and engaging, while stressing scientific literacy and critical thinking.

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