CHAPTER 22
Landscape Development
Chapter Summary• Landscapes are described in terms of their topography: elevation, the altitude of the
surface of the Earth above sea level; relief, the difference between the highest and thelowest spots in a region; and the varied landforms produced by erosion and sedimen-tation by rivers, glaciers, mass wasting, and wind. Elevation is a balance between tec-tonic activity and erosion rate.
• Tectonics (uplift and subsidence), erosion, climate, and the type of bedrock control theevolution of landscapes. Water, wind, and ice act to erode and transport rock materialfrom the high spots and deposit it in the low spots. Over time, relief is subdued by botherosion and sedimentation.
• Landscapes go through different phases depending on tectonic activity and climate.For example, a landscape with high relief will form if tectonic activity is high, whichin turn stimulates erosion. Erosion will at first enhance relief, but over time water,wind and ice will wear down the high spots and fill in the low spots with sediment.
• Current views of landscape evolution emphasize the competition between erosion andtectonic uplift. If uplift is faster, the mountain will rise; if erosion is faster, the moun-tains will be lowered. When tectonics dominates, mountains are high and steep, andthey remain so as long as the balance is in favor of tectonics. When erosion exceedsuplift, slopes become lower and more rounded.
• Mountain building processes dominate convergent plate boundaries. Various feedbackmechanisms may influence evolution of a mountain system at a convergent boundary.As the mountains become higher, glaciers can form. Ice is a very effective agent oferosion. Therefore, negative feedback develops whereas mountains get higher, gla-ciers become bigger and more numerous, and the faster the ice can erode. Over thelong term (tens to hundreds of millions of years) this feedback mechanism probablyspeeds up the wearing down of high mountains. However, over the short term (thou-sands to millions of years) erosion may promote uplift and actually result in the high-est peaks rising even higher, due to isostatic adjustments associated with erosionalunloading.
Learning ObjectivesIn this section we provide a sampling of possible objectives for this chapter. No class could orshould try to accomplish all of these objectives. Choose objectives based on your analysis of yourclass. Refer to Chapter 1: Learning Objectives—How to Define Your Goals for Your Course in theInstructional Design section of this manual for thoughts and ideas about how to go about such ananalysis.
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Knowledge• Know how landscapes are described in terms of their topography: elevation, the alti-
tude of the surface of the Earth above sea level, and relief (the difference between thehighest and the lowest spots in a region).
• Understand how the great variety of landscapes result from sculpturing geologic pro-cesses such as erosion and sedimentation by rivers, glaciers, mass wasting, and wind.
• Understand how landscapes go through different phases depending on tectonic activi-ty and climate.
• Know the major landform provinces for North America.
• Know characteristic landforms associated with active tectonic plate boundaries.
• Understand how Earth systems and plate tectonics control landscapes.
• Understand the relationship between tectonics and erosion.
Skills/Applications/AttitudesChapter 22 provides an opportunity for application of the material in previous chapters. Another wayof saying this is that students, by taking this geology course, have acquired a new set of eyes throughwhich to view the world. It is a good time to test those new eyes with exercises requiring applicationand synthesis.
• Given facts about a region’s elevation, relief, and climate make predictions about thelandforms one would expect to find there.
• Given a particular topography (mesa, cuesta, hogback, valley and ridge topography)sketch and describe its features. Hint: The following figures could be downloaded fromthe instructor’s Web site: aretes (see Figure 22.6), mesas (see Figure 22.8), valley andridge topography (see Figures 22.12 and 22.13), cuestas (see Figure 22.14), hogbacks(see Figure 22.15).
General Education Skills • Write a review of an article out of Scientific American or a professional journal.
(writing/critical thinking)
Freshman Survival Skills• Exam Preparation As the end of the semester approaches students will appreciate
helpful ideas about preparing for finals and taking exams.
• Focused Review This chapter depends heavily on concepts students have been learn-ing throughout the semester. A focused review of previous material will be more ben-eficial than usual. Hint: The section Vital Information at the beginning of Chapter 22of the Student Study Guide for Understanding Earth outlines much of the key materi-al you might choose to review. Consider combining review during lecture with a struc-tured assignment requiring students to do their own review work.
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Chapter 22: Landscapes—Tectonic and Climate InteractionTopography, Elevation, and Relief
Contour linesTopographic maps
LandformsTypes
PlateausMountains and hillsBadlandsMesasHogbacksCuestasRiver and tectonic valleys
Streams and bedrock erosionStream power—dynamic balance between slope, discharge, and sediment loadAbrasion
Tectonics vs. ErosionFeedbacks
Uplift vs. erosionClimate vs. topography
ClimateLatitude
Models for Landscape EvolutionDavis—cycle of erosionHack—dynamic equilibriumPenck—uplift competes with erosion
218 PART II CHAPTER 22
Sample Lecture Outline Sample lecture outlines highlight the important topics and concepts covered in the text. We suggestthat you customize it to your own lecture before handing it out to students. At the end of each chapter outline consider adding a selection of review questions that represent a range of thinking levels.
Teaching Tips Cooperative/Collaborative Exercises and In-Class ActivitiesRefer to Chapter 4: Cooperative Learning Teaching Strategies in the Instructional Designsection of this manual for general ideas about conducting cooperative learning exercises inyour classroom.
Coop Exercise: Landscapes—Tectonic and Climate Interaction FlowchartThe following exercise from the Student Study Guide makes a good in-class exercise. Displaythe flowchart below as a slide or overhead, then have students pair-up with a neighbor to fillin the blanks.
Instructions: Place the following words in the correct positions on the flowchart:
tectonic activity
high relief
low relief
erosion
physical weathering
chemical weathering
General Education Skills• The Geology in Practice exercises offer an opportunity for students to think
about feedback relationships between uplift, erosion and isostatic adjustments.The article entitled “A Review of How Erosion Builds Mountains” by NicholasPinter and Mark T. Brandon, Scientific American, April 1997, pp. 74–79, pro-vides a basis for this investigation. Below is a brief summary of this article.
Major Themes Discussed in How Erosion Builds Mountains:
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uplift
_________weatheringdominates
_________weatheringdominates
e.g., convergentboundary
stimulates
Low relief, hot anddry, tropical
High relief, cold anddry, polar or desert
activationof a plateboundary
— Mountains are a product of plate tectonics, erosion and climate.
— Plate tectonics determines the location of mountain on Earth and plate tec-tonic processes produce the thick crustal root that helps to support manymountain ranges.
— Erosion and climate are closely linked and act together to determine howfast rock is removed off the mountain.
— Erosion coupled with isostatic compensation can result in a positive feed-back, whereas rock is removed from a mountain range by erosion, thebuoyant response of the crustal root results in additional uplift.
Additional Themes:
— Orographic effects can help to determine the ultimate shape of mountains.
— The history of a mountain range can be characterized in three basic stages:
1. Tectonics act to thicken crust and induce uplift at rates greaterthan erosion.
2. Rate of uplift and erosion are about equal, so the highest areaswithin the mountain range can get even higher.
3. Erosion surpasses uplift and the mountain range wears down.
— There is continued debate about the relationship between mountain build-ing and global climate.
Freshman Survival SkillsFocused Review This chapter depends heavily on concepts students have been learningthroughout the semester. A focused review of previous material will be even more beneficialthan usual. Hint: The section Vital Information at the beginning of Chapter 22 in the StudentGuide for Understanding Earth outlines much of the key material you might choose toreview. Consider combining review during lecture with a structured assignment requiring stu-dents to do their own review work. The Study Guide is available in the Understanding Earth e-Book.
Exam Preparation As the end of the semester approaches students will appreciate helpfulideas about preparing for finals and taking exams. Hint: You will find lots of test taking andexam preparation tips in the Student Study Guide and in the teaching tips section of manychapters in this manual. Appendix A is a study plan for preparing for exams, and Appendix Boffers helpful ideas about preparing for final exam week.
• Show slides with exam preparation tips as background during your lecture.
• Provide students a thorough exam review session close to the time of the final.
• Show slides with test taking tips during your exam review section.
• Finally, if you have a class Web site consider posting some materials or linksthat will help students prepare for exams.
Topics for Class DiscussionIntroduce the concept of isostatic adjustment due to loading, e.g., accumulation of ice, andunloading, e.g., the retreat of the ice sheets, erosion of high mountains.
220 PART II CHAPTER 22
Teaching ResourcesStudent Study Guide Highlights In Part I, chapters provide strategies for learning geology. Ideally, students would read thesechapters early in the course.
Chapter 1: Brief Preview of the Student Study Guide for Understanding Earth
Chapter 2: Meet the Authors
Chapter 3: How to Be Successful in Geology
In Part II, Chapter 22: Landscapes—Tectonic and Climate Interaction
Before Lecture:
Preview Questions and Brief Answers
Vital Information from Other Chapters
During Lecture
After Lecture:
Check Your Notes: Have You …
Study Tip: Learn by Drawing
Intensive Study Session
Study Tip for Figure 22.18 and Earth Issues 22.1
Exam Prep:
Chapter Summary
Practice Exercises: Landscapes: Tectonic and Climate Interaction Flowchart
Comparison of Some Landforms
Review questions
Test Taking Tip: Think Logically
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(part of the Understanding Earth e-Book)
