Key Concepts in Geomorphology

Citation

Bierman, P. R., & Montgomery, D. R. (2020). Key Concepts in Geomorphology (2nd ed.). Macmillan Learning.

Chapter Summary

The book has sixteen chapters in four parts, followed by a consolidated list of selected references and further reading and a glossary of the bold key terms. The first edition (2013) was developed with support from the US National Science Foundation as a community-vetted textbook; for the second edition the authors report revising it largely from nearly sixty pages of comments that students and teachers posted to a public revision blog. Every chapter follows the same pattern: learning objectives at the start, thematic sections, usually a section on applications, a "Digging Deeper" essay on how scientific thinking about one problem developed, a case study applying geomorphology to a current problem (listed for thirteen of the sixteen chapters), a worked problem, and end-of-chapter questions ordered to match the learning objectives.

Chapter 1: Earth's Dynamic Surface

The first of three chapters in Part I, Geomorphology and Its Tools: an overview of the surface as the meeting place of geosphere, hydrosphere and biosphere, followed by landscapes and the unifying concepts of the field. The Digging Deeper essay asks why Earth is habitable, and the case study concerns the geomorphic effects of human-induced climate change.

Chapter 2: A Brief History of Geomorphology

New as a full chapter in this edition, it runs from geomythology through classical and natural philosophers and the nineteenth and twentieth centuries to modern geomorphology, with an essay on theories of the Earth and a case study on how the land has been portrayed.

Chapter 3: Geomorphologist's Tool Kit

The methods chapter: characterizing Earth's surface, relative and numerical dating, measuring rates of geomorphic processes, experiments, and proxy records. The Digging Deeper essay explains how a dating method works; the publisher highlights the growth of lidar mapping as one of the edition's updates.

Chapter 4: Geomorphic Hydrology

Part II, Source to Sink, opens with precipitation, evapotranspiration, groundwater and surface water, and the landforms that hydrology produces, with a case study of flooding in Houston and an essay on how human activity links hydrology and landscape change.

Chapters 5–6: Weathering and Geomorphology; Soils and Geomorphology

Formerly a single chapter, now split. Chapter 5 covers physical and chemical weathering, their interactions and weathering-dominated landforms, with acid rock drainage as the case study. Chapter 6 covers soil production, soil development, profiles and description, and soils across landscapes; its essay asks how fast soils form and its case study links soil erosion to the decline of civilizations.

Chapter 7: Hillslopes

Slope-forming materials, mass movements, slope stability, diffusion-like processes and slope morphology, with an essay on the contribution of roots to slope stability and the Oso landslide as case study.

Chapters 8–9: Channels; Drainage Basins

Chapter 8 covers external controls on rivers, fluvial processes, sediment transport, channel patterns, reach-scale morphology, floodplains and channel response, with bedrock incision as the essay topic and the fluvial legacy of the Gold Rush as case study. Chapter 9 moves to basin-scale processes, channel networks and basin morphology, the transition from uplands to lowlands, and urbanization's effects on streams.

Chapter 10: Coastal and Submarine Geomorphology

Coastal settings, drivers, landforms and processes, followed by marine settings and submarine landforms. The essay asks what is happening to the world's deltas, and Superstorm Sandy is the case study.

Chapters 11–13: Wind as a Geomorphic Agent; Volcanic Geomorphology; Glacial and Periglacial Geomorphology

Part III, Ice, Wind, and Fire, covers the remaining agents. Chapter 11 treats air as a fluid, where wind-driven processes occur, and aeolian processes and landforms, with an essay on desert pavements. Chapter 12 covers the distribution and styles of volcanism, eruption mechanisms and sizes, volcanic landscapes and their later evolution, with the 2018 Kīlauea eruption and summit collapse as case study. Chapter 13 covers glaciers, subglacial erosion, glacial transport and deposition, glacial landforms, and periglacial environments.

Chapters 14–16: Geomorphology and Climate; Tectonic Geomorphology; Landscape Evolution

Part IV, The Bigger Picture, draws the process chapters together. Chapter 14 covers climate records and cycles, climatic geomorphology and the two-way relationship between landscapes and climate. Chapter 15 covers tectonic processes and settings and how landscapes respond, with an essay on dating fault movement and the 2018 Alaska earthquake as case study. Chapter 16 takes up the factors, models, types and rates of landscape evolution, asking whether a landscape is in steady state and ending with the Anthropocene.

Key Concepts

Part I: Geomorphology and Its Tools

• Earth's surface as an interface: landscapes form where geosphere, hydrosphere and biosphere interact.
• Relative and numerical dating: ordering landforms in time versus assigning them ages, the basis for measuring process rates.
• Proxy records: indirect evidence used to reconstruct past surface conditions.

Part II: Source to Sink

• Source to sink: the organizing idea of Part II, following water and sediment from weathering on slopes through channels and basins to the coast and sea floor.
• Soil production: the conversion of rock into soil, whose rate the book discusses directly.
• Slope stability and diffusion-like processes: the two ways hillslopes move material, by sudden failure or by gradual creep-like transport.
• Sediment transport and channel response: how rivers move sediment and adjust their form when water or sediment supply changes.

Parts III–IV: Ice, Wind, and Fire; The Bigger Picture

• Aeolian, volcanic and glacial agents: the less universal process domains, each with characteristic landforms.
• Landscape–climate feedbacks: climate shapes landscapes, and landscapes in turn influence climate.
• Tectonic geomorphology: landscapes as records of, and responses to, crustal deformation.
• Steady state: the question of whether uplift and erosion balance so that a landscape keeps its form.

Critical Analysis

Strengths

• Built for first-time learners. The authors describe the book as serving undergraduates in their first course on Earth surface processes, physical geography or Quaternary geology, with eight to sixteen figures per chapter designed for novice readers and twenty to thirty color photographs. The consistent chapter template (objectives, applications, worked problem, questions keyed to the objectives) makes it predictable to study from.
• Community review. The first edition was outlined, drafted and reviewed with broad input from the geomorphology community, and the second edition was revised in response to public comments, which is unusual for a textbook.
• Applications and science in progress. Most chapters have an applications section, and every chapter has a Digging Deeper essay that follows how researchers approached one open question (how fast soils form, how much glaciers erode, whether a landscape is in steady state), which shows geomorphology as a developing science rather than a list of landforms.
• Methods and history given their own chapters. Dating, rate measurement and the history of the discipline are chapters, not appendices, so students meet the tools before the process chapters use them.

Limitations

• Introductory depth. The book is written for a first course, and its contents list one worked problem per chapter; readers who want physically based process models will need a more mathematical treatment.
• Hydrology in a single chapter. Geomorphic hydrology is compressed into Chapter 4; students in a combined geomorphology and hydrology course will need a dedicated hydrology text.
• Uneven case-study coverage. The publisher lists case studies as a feature of every chapter, but its own contents list shows none for Chapters 11, 13 and 14, which instead carry chapter-level reference lists.

Where It Fits in the Course

In the geomorphology and hydrology list the book is the standard-length introductory textbook. Goudie and Viles's Landscapes and Geomorphology: A Very Short Introduction is a brief overview of the discipline that can be read before it, and Huggett and Shuttleworth's Fundamentals of Geomorphology is a second broad introductory textbook, organized around process systems and landscape change, that works as an alternative main text or a source of second explanations. Anderson and Anderson's Geomorphology: The Mechanics and Chemistry of Landscapes builds each topic from conservation laws and simple models and is the natural step after Bierman and Montgomery for students who want the physics behind the processes.

For the hydrology side of the course, Hendriks's Introduction to Physical Hydrology is a compact introductory treatment of atmospheric, soil, ground and surface water that extends Chapter 4, and Dingman's Physical Hydrology is the quantitative text to read after it.

How to Use This Book

The book suits students in a first geomorphology, physical geography or Quaternary geology course, and the authors also have students in forestry, agriculture and civil engineering in mind. An introductory geology or physical geography course helps.

A reading plan:

• Core: Chapters 1 and 3 (the tool kit is used throughout), then Part II in order, Chapters 4–10, since it follows sediment from source to sink and each chapter builds on the previous one.
• Selective: Part III by region and interest; glacial and periglacial geomorphology (Chapter 13) is the most widely relevant, while wind and volcanic chapters can be chosen to match fieldwork areas.
• Synthesis: Chapters 14–16 at the end of the course, where they draw the process chapters together. Chapter 2 on history can be read early or alongside a geographic thought course.

Start each chapter with its learning objectives and finish by answering the end-of-chapter questions, which follow the order of the text. Do the worked problem by hand. Read the Digging Deeper essays as models of how a research question is framed, and use the case studies for discussion or short written assignments. The glossary and the end-of-book reference list support revision and further reading.