The changing focus of geomorphic research suggests that the time is right to summarize the state of the discipline. The number of peer-reviewed papers published has grown steadily for 20+ years, and author diversity has expanded dramatically. As more are drawn to geomorphology, summarizing contemporary geomorphic knowledge has become more difficult. The 14 volumes of the Treatise on Geomorphology are an important reference for undergraduate students seeking term paper topics, graduate students starting a literature review, and professionals looking for topic summaries. The historical development of geomorphology topics provides context for ongoing research; discussion of research strategies, equipment, field methods, laboratory experiments, and numerical simulations reflect multiple approaches to understanding Earth's surfaces. Outstanding research questions highlight future challenges and suggest new avenues for research. Our ability to adapt to geomorphic changes hinges on how well landform scientists comprehend the dynamics of Earth's surfaces. This treatise synthesizes the state of the discipline, highlighting productive research directions. Geomorphology has advanced greatly in the last 10 years to become an interdisciplinary field. Undergraduate students, graduate students, and professionals will find answers in this broad reference work. Editor-in-Chief Prof. J. F. Shroder of the University of Nebraska at Omaha is past president of the QG&G section of the Geological Society of America and present trustee of the GSA Foundation. Many noted international geomorphologists have contributed state-of-the-art chapters. Every chapter has been critically reviewed for consistency and accuracy. No other reference work in geomorphology offers the breadth and depth of information of this treatise.