Solution Manual for Earth: An Introduction to Physical Geology, 12th Edition

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1ANINTRODUCTION TOGEOLOGY1INTRODUCTIONAn Introduction to Geologycovers the fundamental ideas and concepts of geologic study. Fundamentalconcepts of historical geology, including catastrophism, uniformitarianism, and geologic time, providea context to the study of geology. A discussion of scientific inquiry aids in understanding how geologicprocesses and materials are studied and understood. The chapter provides a brief discussion ofEarth’s spheres, including the hydrosphere, atmosphere, biosphere, and geosphere, and discussesEarth systems science as a means of understanding the interconnectedness of these spheres. Thechapter then discusses the formation of the solar system, Earth, and the fundamental concepts ofdensity and buoyancy in understanding Earth structure. This leads to a discussion of Earth’s layeringand the rock cycle operating at and beneath Earth’s surface. The chapter ends with a discussion of themajor physicalfeatures of the Earth’s surface, including those of the continents and ocean basins.CHAPTEROUTLINE1.Geology: The Science of Eartha.Geology is the science that pursues an understanding of planet Earthi.Earth is a dynamic body with many interacting parts and a complex historyii.Earth is continuously changing, both rapidly and slowly, and internally andexternallyb.Physical geology and historical geologyi.Physical geology1.Examines the materials composing Earth2.Seeks to understand the many processes that operate beneath and upon itssurfaceii.Historical geology1.Attempts to understand the origin of Earth and its development through time2.Establishes an orderly chronological arrangement of changes in Earth’sgeologic pastiii.Physical and historical geology is further subdivided into many areas ofspecializationc.Geology, people, and the environmenti.The problems and issues addressed by geology are of practical value to peopleii.Natural hazards1.Natural processes become hazards when people live where they occur2.Volcanoes, floods, tsunami, earthquakes, and landslides3.Urbanization makes people more vulnerable to hazardsiii.Resources1.Water and soil, metallic and nonmetallic minerals, and energy2.Form foundation of modern civilization

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2iv.Processes1.Humans are impacted by, and have an impact on, geologic processes2.Example: landslides and river flooding are affected by human activities, butalso pose threats to humansv.Basic geologic knowledge and principles are needed to understand environmentalproblems2.The Development of Geologya.Begins with writings of Greeks, more than 2300 years agob.Aristotlei.Influential philosopherii.Inaccurate explanations about the natural worldiii.Based on keen observations and experimentsiv.Continued to be viewed as authoritative for many centuries, inhibiting moreup-to-date ideasc.Post 1500s—Catastrophismi.In 1600s, James Ussher calculated that Earth was only a few thousand years old(began 4004 BC)1.This number earned widespread acceptance in science and religionii.Led to idea thatEarth’s landscapes had been shaped primarily by great catastrophesiii.Produced by sudden and often worldwide disasters produced by unknowablecauses that no longer operateiv.This philosophy was an attempt to fit the rates of Earth processes to the then-current ideas on the age of Earthd.Birth of modern geologyi.Uniformitarianism1.Physical, chemical, and biological laws that operate today have also operatedin the geologic past2.Commonly stated asthe present is the key to the past3.Forces and processes that we observe presently shaping our planet havebeen at work for a very long timeii.Hutton’sTheory of the Earthpersuasively argued that forces that appear smallcould, over long spans of time, produce effects1.Carefully cited verifiable observations to support his idease.Geology todayi.Present gives us insight into the pastii.The physical, chemical, and biological laws that govern geological processes remainunchanging through timeiii.Does not suggest that they always had the same relative importance or that theyoperated at precisely the same rateiv.Some important geologic processes are not currently observable, but evidence thatthey occur is well establishedv.Grand Canyon provides a good example (Figure 1.5)

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3f.The magnitude of geologic timei.Earth has a very long and complex historyii.Early time scales placed the events of Earth’shistory in order without knowing howlong ago, in years, they occurrediii.Today, radioactivity allows us to accurately determine numerical dates for rocksthat represent important events in Earth's distant pastiv.Today, the age of Earth is put at about 4.6 billion years3.The Nature of Scientific Inquirya.Science is a process of making careful observations and creating explanation to produceknowledge about the natural worldi.Assumption: the natural world behaves in a consistent and predictable manner thatis comprehensible through careful, systematic studyii.Goal: discover the underlying patterns in nature and then use this knowledge tomake predictions about what should or should not be expected, given certain factsor circumstancesb.Development of new scientific knowledge involves some basic logical processes that areuniversally acceptedc.Hypothesisi.A tentative (or untested) explanation of an observation or dataii.Predictions are made based on the hypothesis being considered and the predictionsare testediii.If a hypothesis cannot be tested, it is not scientifically usefuliv.Those hypotheses that fail rigorous testing are ultimately discardedd.Theoryi.Well-tested and widely accepted view that the scientific community agrees bestexplains certain observable factsii.Example—theory of plate tectonicse.Scientific methodsi.Process of gathering facts through observations and formulating scientifichypotheses and theoriesii.Not a standard recipe that scientists apply in a routine manner—An endeavor thatinvolves creativity and insightiii.Many scientific investigations involve the following:1.A question is raised about the natural world2.Scientific data are collected that relate to the question3.Questions are posed that relate to the data and one or more workinghypotheses are developed that may answer these questions4.Observations and experiments are developed to test the hypotheses5.The hypotheses are accepted, modified, or rejected based on extensivetesting6.Data and results are shared with the scientific community for criticalexamination and further testing.iv.Best to describe the nature of scientific inquiry as the methods of science

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4f.Plate tectonics and scientific inquiryi.Early 20th century—continental drift1.The idea that the continents moved about the face of the planet2.Contradicted the established view that the continents and ocean basins arepermanent and stationary featuresii.50 years later—plate tectonics1.Enough data were gathered to transform this controversial hypothesis2.A sound theory that wove together the basic processes known to operateon Earth3.Provided geologists with the first comprehensive model of Earth’s internalworkings4.Earth as a Systema.Earth is a dynamic body of four interacting spheres: the hydrosphere, atmosphere,geosphere, and biosphereb.Parts are not isolated; relate to each other in a continuously interacting whole–Earthsystemc.Earth’s spheresi.Hydrosphere1.Dynamic mass of water that is continually on the move2.Evaporating from the oceans to the atmosphere, precipitating to the land,and running back to the ocean again3.Ocean—71 percent of Earth’s surface, and 97 percent of Earth’s water4.Also glaciers, streams, and groundwaterii.Atmosphere1.Earth’s thin gaseous envelope2.Provides the air that we breathe3.Protects us from the Sun’s intense heat and dangerous ultravioletradiation4.Energy exchanges between the atmosphere and Earth’s surface produceweather and climateiii.Biosphere1.All life on Earth2.Most life on land is also concentrated near the surface3.Life forms help maintain and alter the physical environmentiv.Geosphere1.The solid Earth beneath the atmosphere and oceans2.Extends from the surface to the center of the planet, a depth of nearly6400 kilometers

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5v.Examples of interactions of all spheres: soil, thethin veneer of material at Earth’ssurface that supports the growth of plants, may be thought of as part of all fourspheres1.Weathered rock debris (geosphere)2.Organic matter from decayed plant and animal life (biosphere)3.Rock debris is the product of weathering processes that require air(atmosphere) and water (hydrosphere)4.Air and water also occupy the open spaces between the solid particlesd.Earth system sciencei.Aims to study the Earth as a system composed of numerous interacting subsystemsii.Integrates interdisciplinary knowledge (geology, atmospheric science, chemistry,biology, etc.)iii.A system is a group of interacting, or interdependent, parts that form a complex wholee.The Earth systemi.The Earth system has a nearly endless array of subsystems in which matter isrecycled over and over again1.Examples: Hydrologic cycle, carbon cycle, rock cycle2.Parts of the Earth system are linked so that a change in one part can producechanges in any or all of the other parts3.Characterized by processes that vary on spatial scales from fractions ofmillimeters to thousands of kilometersii.The Earth system is powered by energy from two sources1.Sun—drives weather and climate, ocean circulation, and erosional processes2.Earth’s internal heat—powers the internal processes that producevolcanoes, earthquakes, and mountainsiii.Humans are part of the Earth system and our actions produce changes in all of theother parts5.Origin and Early Evolution of Eartha.Origin of our solar systemi.The universe begins1.Big Bang—13.7 billion years ago, formed the universeii.The solar system forms1.Nebular theory—Solar system evolved from an enormous rotating cloudcalled the solar nebula2.Composed of hydrogen and helium atoms generated during the Big Bang,and microscopic dust grains and ejected matter of long-dead stars3.About 5 billion years ago, the nebula began to contract and formed a flat,disk-shape with a concentration of material around a protosun in its center

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6iii.Inner planets form1.Formed from metallic and rocky clumps of substances with high melting points2.The elements of which the rock-forming minerals are composed—silicon,calcium, sodium3.Repeated collisions caused these masses to coalesce into larger asteroid-sizebodies, calledplanetesimalsa.Mercury, Venus, Earth, and Mars4.Rocky and metallic pieces that remained in orbit are calledmeteoritesiv.Outer planets develop1.Larger outer planets began forming from fragments with a high percentageof ice of water, carbon dioxide, ammonia, and methane2.Jupiter, Saturn, Uranus, and Neptuneb.Formation of Earth’s layered structurei.As Earth formed, the decay of radioactive elements and heat from high-velocityimpacts caused the temperature to increaseii.Chemical differentiationin Earth’slayers1.Iron and nickel began to melt and sink toward the center2.Lighter rocky components floated outward, toward the surfaceiii.An atmosphere develops1.Gaseous material escaped from Earth’s interior to produce the primitiveatmosphereiv.Continents and ocean basins evolve1.Continents and ocean basins formed gradually over the last 4 billion years6.Earth’s Internal Structurea.Earth’s internal layers can be defined by chemical composition, and/or physical propertiesb.The nature of Earth’s interior is determined by analyzing seismic waves from earthquakesc.Earth’scrusti.Thin, rocky outer skin1.Oceanic crusta.Seven kilometers (5 miles thick)b.Composed of dark igneous rocks called basalt2.Continental crusta.Averages 35–40 kilometers (25 miles) thickb.Upper crust has an average composition of a granitic rock,granodiorite, but varies from place to place3.Continental crust rocks are less dense and older than oceanic crust rocksd.Mantlei.More than 82 percent of Earth’s volumeii.Solid, rocky shell, extends to a depth of 2900 kilometers (1800 miles)iii.Dominant rock in the uppermost mantle is peridotiteiv.Upper mantle1.Crust-mantle boundary to depth of 660 kilometers (410 miles)2.Lithosphere—uppermost mantle, relatively cool, outer shella.Thicker below continents, thinner below oceans

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73.Asthenosphere—soft, relatively weak layera.Small amount of melting at the top allows lithosphere to bemechanically detached from asthenosphereb.Lithosphere can move independently of asthenosphere4.Strength of layers is based on composition and temperature of theirenvironmenta.Rocks get progressively hotter and weaker with depth in thelithosphere5.At transition zone (660 km [410 miles]) we see a sudden increase in densitya.Minerals in peridotite respond to increased pressure to form newminerals with closely packed atomic structuresv.Lower mantle1.660 kilometers (410 miles) to 2900 kilometers (1800 miles)2.Mantle gradually strengthens with depth due to increase in pressure3.Rocks are very hot, and capable of gradual flow4.Dˈˈlayer is boundary between rocky mantle and hot liquid iron outer coree.Corei.Composed of an iron-nickel alloy with minor amounts of oxygen, silicon, and sulfurii.Due to the extreme pressure found in the core, the density is nearly 11 g/cm3iii.Divided into two regions with different mechanical strengths1.Outer core is a liquid layer 2250 kilometers (1395 miles) thicka.Movement of metallic iron in outer core generates Earth’s magneticfield2.Inner core is a solid sphere with a radius of 1221 kilometers (757 miles)a.Extremely hot, but solid due to immense pressure at center of Earth7.Rocks and the Rock Cyclea.Rocks are composed of mineralsi.Minerals—chemical compounds or single elements with their own compositionand physical propertiesii.Nature and appearance of a rock influenced by its mineralsiii.Texture refers to the size, shape, and arrangement of minerals in a rockiv.Mineral composition and texture reflect the geologic processes that createdthe rockb.Rocks are divided into three major groups—igneous, metamorphic, and sedimentaryi.The rock cycle helps us understand the origin of each group and the processes thatform eachii.Rocks continuously change from one form to another due to natural Earth processesc.The basic cyclei.Igneous rock1.Rocks formed from cooling and solidification (crystallization) of moltenmaterial (magma)ii.Sedimentary rock

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81.Pre-existing rocks weather and erode into pieces, called sediment2.When sediment is compacted and/or cemented, it turns to rock, in a processcalled lithificationiii.Metamorphic rock1.When rocks are buried deep in the Earth, or intruded by magma, they aresubjected to great heat and pressure2.Rock reacts to changing environment and becomes a different rockiv.Internal processes driven by heat from Earth’s interior create igneous andmetamorphic rocksv.External processes powered by the energy of the Sun cause the weathering anderosion that form sediment and sedimentary rocksd.Alternative pathsi.Igneous rocks become metamorphic rocks if subjected to strong compressionalforces and high temperatures in mountain buildingii.Metamorphic, igneous, and sedimentary rocks can weather to become sedimente.Rock cycle processes take very long amounts of time, but we can observe all parts of thecycle in different locations on Earth8.The Face of Eartha.Earth’s surface—continents and ocean basinsi.Significant difference between their relative levels, due to different thicknesses anddensitiesii.Continents are thicker, less denseiii.Ocean basins are thinner, more denseiv.As a result, continental crust floats on top of the deformable rocks of the mantle at ahigher level than oceanic crustb.Major features of the ocean floori.Ocean floor has volcanoes, deep canyons, plateaus, and flat plainsii.Oceanographers use depth-sounding equipment and satellite technology tounderstand the shape of the ocean flooriii.Three major regions1.Continental marginsa.Continental shelf—a gently sloping platform of continental material,extends seaward from the shoreb.Continental slope—a steep drop-off at the outer edge of the continentalshelf, marks the boundary between the continents and the deep-oceanbasinc.Continental rise—a thick wedge of sediment that moved downslopefrom the shelf and accumulated on the deep seafloor

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92.Deep-ocean basinsa.Located between the continental margins and oceanic ridgesb.Featuresi.Abyssal plain—flat, featureless areasii.Trenches are long, narrow canyons on the ocean flooriii.Some trenches are located adjacent to young mountains that flankthe continents while others parallel linear island chains calledvolcanic arcsiv.Seamounts—submerged volcanic structures on the ocean floor1.Volcanic activity also produces lava plateaus3.Oceanic ridgesa.The most prominent topographic feature on the seafloorb.Continuous belt that winds for more than 70,000 kilometers aroundthe globec.Composed of layered igneous rock that has been fractured and upliftedc.Major features of the continentsi.Mountain belts1.Uplifted regions of deformed rocks2.Two major zonesa.Circum-Pacific belt surrounding the Pacific Oceani.Mountains of the western Americas and western Pacific volcanicisland arcsb.Area eastward from the Alps through Iran and the Himalayas, andsouthward into Indonesiai.Thick sequences of rocks have been squeezed and highlydeformed, as if placed in a gigantic viseii.The stable interior1.Cratons—relatively stable interior of continents; undisturbed for the past600 million years or longer2.Shields—expansive, flat regions on the craton composed of deformedigneous and metamorphic rocks3.Stable platforms—flat areas where the shields are covered by a thin veneerof sedimentary rocksd.Understanding the topographic features of Earth helps us to better understand themechanisms that shaped the planet in the geologic past, and will shape the planet inthe futureLEARNINGOBJECTIVES/FOCUS ONCONCEPTSEach statement represents the primary learning objective for the corresponding major headingwithin the chapter. After completing the chapter, students should be able to:

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101.1Distinguishbetween physical and historical geology and describe the connections betweenpeople and geology.1.2Summarizeearly and modern views on how change occurs on Earth and relate them to theprevailing ideas about the age of Earth.1.3Discussthe nature of scientific inquiry, including the construction of hypotheses and thedevelopment of theories.1.4List and describeEarth's four major spheres.Definesystemand explain why Earth isconsidered to be a system.1.5Outlinethe stages in the formation of our solar system.1.6SketchEarth’s internal structure and label and describe the main subdivisions.1.7Sketch, label, and explainthe rock cycle.1.8List and describethe major features of the continents and ocean basins.TEACHINGSTRATEGIESIntroduce the Science of Geology:The first chapter of the book is a good time to discuss what ageologist does, and the science of geology. This activity helps students to know their own role andinterest in geology, while allowing the instructor to review writing styles of the class.Calibrated Peer Review Activity—“Why Study Geology”:http://serc.carleton.edu/introgeo/peerreview/examples/why_study_geo.htmlMuddiest Point:In the last 5 minutes of class, have students jot down the points that were mostconfusing from the day’s lecture, and what questions they still have. Or provide a “self-guided”muddiest point exercise, using the “CRS”PowerPoints, textbook Concepts in Review, and websitequestions for this chapter. Review the answers, and cover the unclear topics in a podcast to theclass or at the beginning of the next lecture.The following are fundamental ideas from this chapter that students have the most difficultygrasping.A.Nature of Sciencea.Students come to an intro-level science course thinking that science is the objectiveaccumulation of facts and science is always done following the exact steps of thescientific method. Getting students to think of science as an inquiry process isdifficult, and should be reiterated throughout the semester. The fundamentalconcept of scientific inquiry can be explained to your students with this chapter, asthe foundation of the remaining chapters. Urge your students to continuously thinkabout “How do weknow what we know?”b.Guided Reading of a Scientific Article:http://serc.carleton.edu/NAGTWorkshops/structure/activities/47021.htmlc.How many sand grains on a beach?http://serc.carleton.edu/quantskills/activities/14846.html

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11d.Thinking Scientifically:http://serc.carleton.edu/introgeo/indoorlabs/examples/21805.htmlB.Geologic Timea.Geologic time is difficult for a student to understand. Ask students to think aboutwhat is “old” to them. They will say things like grandma, the United States, a car,andso on. Ask them what is “ancient.” They will likely think of things like redwood trees,Indian artifacts, the Bible, and so on. This can lead into a discussion of what is youngand old to geologists. Cite specific Earth events and geologic events from your ownregion. Then, have students calculate how long it would take to count to 4.6 billion(the answer is in the text, but this is a useful exercise in unit conversion).b.Big Numbers and Scientific Notation:http://serc.carleton.edu/quantskills/methods/quantlit/BigNumbers.htmlc.How big is a billion?http://serc.carleton.edu/quantskills/activities/UndBigNos.htmlC.Earth Structurea.Many students believe the entire Earth is molten beneath the surface (or evenhollow—thanks, Hollywood!). Students have difficulty visualizing the interiorstructure of the Earth, so animations are helpful in helping them make thesevisualizations. Also provide alternative readings on HOW we know the structureand composition of the inside of the Earth.i.USGS “The Interior of the Earth”:http://pubs.usgs.gov/gip/interior/ii.Scientific Evidence for Structure of Earth’s Interior:http://www.columbia.edu/~vjd1/earth_int.htmhttp://www.columbia.edu/~vjd1/earth_int.htmb.Good Imagery and Models:http://crack.seismo.unr.edu/ftp/pub/louie/class/100/interior.htmlD.Humans and Eartha.Students often think that humans cannot affect Earth processes, and therefore ouractions are insignificant when thinking about Earth as a system. This concept shouldbe addressed throughout the course, and in more detail in an EnvironmentalGeology course. Here, when discussing Earth as a system, it is important to providea few examples of how humans affect Earth processes.b.A few articles to help you think about this:i.http://geology.geoscienceworld.org/content/33/3/161.abstractii.http://www.sciencemag.org/content/277/5325/494.abstractc.And, a fun debate for class: Have humans created a new geologic age?i.http://www.newscientist.com/blog/environment/2008/01/have-humans-created-new-geological.htmlii.http://www.livescience.com/25332-anthropocene-humans-geologic-era.htmliii.http://www.smithsonianmag.com/science-nature/what-is-the-anthropocene-and-are-we-in-it-164801414/?no-ist

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12TEACHERRESOURCESTeaching 100-level Geoscience CoursesThe SWERC Carleton website offers many resources to help you with teaching introductoryscience courses:http://serc.carleton.edu/NAGTWorkshops/intro/index.htmlScientific Inquiry and GeosciencesMcLelland, Christine V., “The Nature of Science and the Scientific Method,” The GeologicalSociety of America, August 2006.http://www.geosociety.org/educate/NatureScience.pdfWhat do geoscientists do?ohttp://www.agiweb.org/workforce/brochure.htmlohttp://geology.com/articles/what-is-geology.shtmlohttp://www.bls.gov/ooh/Life-Physical-and-Social-Science/Geoscientists.htmGeologic TimeGraphical Representation:http://pubs.usgs.gov/gip/geotime/time.htmlClock of Eras:http://www.fossils-facts-and-finds.com/clock_of_eras.htmlUSGS and NPS “What is?”:http://www2.nature.nps.gov/geology/usgsnps/gtime/gtime1.htmlOther Visualizations:http://serc.carleton.edu/NAGTWorkshops/time/teaching_visualizations.htmlThis activity can help students visualize the span of geologic time:http://www.geologyclass.org/Geologic%20Time%20Scale%20Activity.htmThis website gives you specific information, pictures, and histories of each geologic timeperiod:http://www.ucmp.berkeley.edu/help/timeform.htmlGeological Society of America Geologic Time Scale:http://www.geosociety.org/science/timescale/Cycles on Earth:Rock Cycle:http://ansatte.uit.no/kku000/webgeology/webgeology_files/english/rocks.htmlWater Cycle:http://www.montereyinstitute.org/noaa/lesson07.htmlCarbon Cycle:http://earthobservatory.nasa.gov/Features/CarbonCycle/Plate Tectonics:http://www2.nature.nps.gov/geology/usgsnps/animate/pltecan.htmlAkid’swebsite, but a good introduction to cycles covered later:http://www.eo.ucar.edu/kids/green/cycles1.htm

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13ANSWERS TOQUESTIONS IN THECHAPTER:CONCEPTCHECKS1.11.Name and distinguish between the two broad subdivisions of geology.Physical geology isthe study of materials composing the Earth (minerals, rocks, water, etc.) and the processesthatoperate upon and below Earth’s surface (plate tectonics, rock formation, deformation,erosion, etc.). Historical geology aims to understand the origin of the Earth and itsdevelopment through time. This study establishes an orderly chronological arrangement ofevents and changes of the geologic past by study of the origin of rocks, the movements of platesover time, and the occurrence of ancient environments and life forms as displayed in thegeologic record. These two areas of study are subdivided into many more areas ofspecialization.2.List at least three different geologic hazards.Geologic hazards are natural Earth processesthat adversely affect humans. Examples of geologic hazards include earthquakes, volcaniceruptions, floods, tsunami, and landslides. Humans can also exacerbate natural Earth processes,creating hazards, by interfering with natural processes. Examples include the increasedflooding hazards created by the clearing of forests, building cities, and constructing dams.3.Aside from geologic hazards, describe another important connection between peopleand geology.Earth resources, formed by Earth processes, have tremendous value to humans.These resources include water, soil, metallic and nonmetallic minerals, and energy. Theextraction and use of these resources have many environmental impacts.1.21.Describe Aristotle’s influence on geology.Aristotle was a Greek philosopher whose writingsinfluenced early understanding of the Earth. Unfortunately, Aristotle’s ideas were not based onstudy and observation, but simply his own opinions of how the natural world worked. Theseideas were viewed as authoritative explanations for many centuries, slowing the progress ofstudy based on observations, until Renaissance thought pushed more detailed study of theEarth.2.Contrast catastrophism and uniformitarianism. How did each view the age of Earth?Catastrophism viewed the Earth as being shaped by great catastrophes—sudden andworldwide disasters produced by unknowable processes that no longer operate. Catastrophismwas based on the idea that Earth formed in 4004 BC as calculated by biblical scholar JamesUssher in 1660. Conversely, uniformitarianism (now a fundamental concept of geology) viewsEarth processes as happening over very long time periods, and those processes that we seeoperating today also operated in the geologic past. The common idea of uniformitarianism is“the present is the key to the past.” This concept understands that Earth is much older thanthought by catastrophism, and processes that operate continually on and beneath its surfacecreated (and continue to create) the features we see.

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143.How old is Earth?Today, the age of Earth is put at about 4.6 billion years. This age is basedon scientific study of the radioactivity of rocks, as will be discussed in Chapter 9.4.Refer to Figure 1.6 and list the eon, era, period, and epoch in which we live.PhanerozoicEon, Cenozoic Era, Quaternary Period, Holocene Epoch.5.Why is an understanding of the magnitude of geologic time important for a geologist?An understanding of geologic time is essential to geologic study because many processesstudied are so gradual that vast spans of time must pass before noticeable and significantchanges occur. For example, the rocks of the Grand Canyon (Figure 1.5) were created overmillions of years, and it took many more millions of years for the Colorado River to erode downthrough these rocks to the display we see today.1.31.How is a scientific hypothesis different from a scientific theory?A scientific hypothesis is atentative, untested explanation of a natural phenomenon. Generally, scientists formulate morethan one hypothesis to explain their observations. A fundamental caveat of a hypothesis is thatit must be testable (able to pass objective testing and analysis); if it cannot be tested, it is notscientifically useful. Hypotheses may be accepted when evidence demonstrates that they arecorrect, but also may be rejected when they fail rigorous testing. The Earth-centered model ofthe universe is an example of a hypothesis that, once tested, was rejected as an explanation ofthe orientation of our planet in the solar system.A scientific theory is a well-tested hypothesis that has gone through extensive testing andscrutiny. It is a well-tested and widely accepted view that the scientific community agrees bestexplains a natural phenomenon. Theories generally include several well-tested, acceptedhypotheses to explain a larger scale process or phenomenon on Earth. An example of a theoryis the Theory of Plate Tectonics, which will be discussed in Chapter 2.2.Summarize the basic steps followed in many scientific investigations.The scientificmethod is the process by which researchers gather facts through observations and formulatescientific hypotheses and theories. Although this method does not always follow a fixed path, itdoes involve: (1) a question about the natural world, (2) data collection related to thatquestion, (3) formulation of one or more hypotheses to explain the question and data, (4)observation and experiments to test the hypothesis, (4) the acceptation, modification, orrejection of the hypothesis based on extensive testing, and (5) sharing data and results withthe scientific community for further testing and critical examination. See Figure 1.9.1.41.List and briefly describe the four spheres that constitute the Earth system.Thehydrosphere is the dynamic mass of water at Earth’s surface, including water in the oceans,atmosphere, lakes and rivers, glacial ice, and groundwater. Water moves about thehydrosphere via the water cycle through processes such as evaporation, transpiration, runoff,precipitation, and infiltration.

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15The atmosphere is the gaseous layer surrounding Earth’s surface. This layer comprises the airwe breathe, protects Earth from harmful ultraviolet radiation, and creates the weather andclimate we experience at the surface.The biosphere is all life on Earth. The biosphere includes plants and animals living on andabove Earth’s surface, within the oceans, and underground.The geosphere is the solid earth extending from the surface to the center (core) of Earthincluding both consolidated (rock) and unconsolidated (sediment) earth material. Thegeosphere includes rock and sediment at the surface, bedrock beneath and at the surface, andthe materials making up the layers deep within the Earth.2.Compare the height of the atmosphere to the thickness of the geosphere.Ninety percentof Earth’s atmosphere is located within 16 km (10miles) of the surface. Compared to thegeosphere, which comprises the entire inner Earth to a depth of 6400 km (4000miles), theatmosphere is an extremely thin veneer on the surface of the Earth.3.How much of Earth’s surface do oceans cover? What percentage of the Earth’s watersupply do oceans represent?Earth’s oceans cover 71percent of its surface and represent 97percentof Earth’s water supply.4.What is a system? List three examples.A system is a group of interacting, orinterdependent, parts forming a complex whole. The Earth system is comprised of individualcomponents such as land, water, air, and life (Earth’s spheres) that are interconnected andinteract to create the processes we see at the surface. Examples of systems operating on Earthinclude the rock cycle (the recycling of rock from one form to another), the hydrologic cycle(the movement of water about and beneath the surface), and the carbon cycle (the exchange ofcarbon between the air, life, and rocks).5.What are the two sources of energy for the Earth system?The Earth system is powered byenergy from the Sun and from heat energy generated from Earth’s interior. Energy from theSun drives processes in the atmosphere and hydrosphere such as weather, climate, oceancirculation, and erosional processes. Energy from the Earth’s interior is continuouslygenerated by radioactive decay and powers internal Earth processes such as volcanism,earthquakes, and mountain-building.1.51.Name and briefly outline the theory that describes the formation of our solar system.The nebular theory says that the bodies of our solar system evolved from an enormous rotatingcloud of microscopic dust grains and ejected matter of dead stars. This cloud of gasses, called asolar nebula, began to contract about 5 billion years ago due to gravitational interactions ofthe particles. As it contracted, it rotated faster and faster, and a flat disk with a centralprotosun formed. The gravitational energy of the rotating nebula converted to thermal energyallowing dust particles to break into molecules. When heating ceased, these moleculescoalesced into the planets—with the inner planets (Mercury, Venus, Earth, and Mars)composed of the heavier elements of the cloud and the outer planets (Jupiter, Saturn, Uranus,and Neptune) of the lighter elements.

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