Charles Andrew Cotton, born in Dunedin on 24 February 1885, was the only son of Scottish-born Margaret Thomson McCallum and her husband, Charles Henry Cotton, a Cornish mariner. His parents had met while sailing to New Zealand in the early 1880s and were married in Dunedin in February 1884. Charles senior became a master of trading vessels, and his wife and son accompanied him on many of his voyages, sometimes as far as the Gilbert Islands and Mauritius. Most of Charles's early education was provided by his mother.
From 1899 Charles lived with his maternal grandmother at Linwood, Christchurch, and attended Christchurch Boys' High School. There, a schoolmate's thoughtless prank cost him the sight in his left eye. Although a considerable handicap in adult life (for example, he could not use a stereoscope), the accident did not hinder Cotton's outstanding academic career: he gained a Junior Scholarship, and later, at the University of Otago, was awarded a Sir George Grey Scholarship and was senior scholar in physics. He graduated with an MSc in 1908, with first-class honours in geology.
On leaving Otago University Charles Cotton was director of the Coromandel School of Mines for two years, and was engaged in petrological and mining surveys of the Hauraki goldfields. In 1909 he moved to Wellington to become the first lecturer in geology at Victoria College. The college's location had disadvantages: weekend field excursions were an essential part of student practical work, but the rocks of the Wellington district had little variety, and there was no easy access to Wairarapa, which had a more interesting geology. This may have influenced Cotton's move to geomorphology, the study and analysis of landscapes. He had developed an interest in landforms on earlier field trips in North Canterbury and Marlborough with J. Allan Thomson, and also through the inspiration and encouragement of J. A. Bartrum, later professor of geology at Auckland University College.
Studies of the Wellington landscape were fundamental to the development of Cotton's ideas on the landforms produced by long-term earth movements combined with erosion. Working in relative academic (and geographic) isolation in the early 1900s, Cotton had the advantage of living in a small country with a wide variety of geological features, climates and rates of geomorphic change. He also drew inspiration from the writings of the American physiographers J. W. Powell, G. K. Gilbert and, in particular, W. M. Davis. Davis had pioneered an approach that involved the systematic description and interpretation of landforms through precise field observation. Explanations of the progressive development of landforms were often illustrated by sequential diagrams proceeding from an initial stage through to maturity. Cotton extended this approach by demonstrating that geomorphology could provide important insights into not only the more recent geological history of a region, but also the nature and structure of the underlying rocks, and their tectonic history during different geological periods.
In 1912 Cotton published his first geomorphological paper, 'Notes on Wellington physiography'. With its closely reasoned text, illustrated with carefully selected figures and Cotton's characteristic line drawings, the paper introduced a new standard of description and explanation to New Zealand geomorphology. His contact with Davis during the latter's visit to New Zealand in 1914 confirmed his belief in the importance of geomorphology and the value of Davis's interpretive methods, a view he was to retain throughout his life.
In 1915 Cotton was awarded a DSc and made an associate of the Otago School of Mines. In 1921 he was elected a fellow of the New Zealand Institute. In the same year he became a full professor at Victoria University College, a position he was to hold until his retirement in 1953. On 17 July 1926, at Auckland, he married Hilda Mary Josephine Gibbons, who was also the child of a master mariner. They were to have a son and a daughter.
In the decade after 1912 Charles Cotton produced a number of acclaimed papers and reviews, and in 1922 he published his first book, Geomorphology of New Zealand. This quickly became a standard textbook and received international recognition as an outstanding summary of the general principles and applications of the study of landforms. It was reprinted seven times, the third edition being revised, enlarged, and issued in 1942 as Geomorphology. (A planned second volume, intended to offer a more detailed regional treatment, was never completed.)
Over the following years Cotton maintained a steady flow of papers and reviews. Three further books, Landscape as developed by the processes of normal erosion (1941), Climatic accidents in landscape-making (1942), and Volcanoes as landscape forms (1944), consolidated his reputation as one of the world's leading geomorphologists. New Zealand geomorphology, published in 1955, brought together 16 of Cotton's influential papers from 1912 to 1925. A similar collection on coastal geomorphology, Bold coasts, was published posthumously in 1974. Although he was strongly influenced by W. M. Davis, Cotton never adhered blindly to his theories, and his later works acknowledge the views of Davis's critics.
Victoria University College had relatively few geology students until the mid 1950s, and for many years Cotton taught without the assistance of even a demonstrator to take practical classes. In addition to his own geology classes, he gave weekly lectures on geomorphology to first-year geography students. Cotton had little enthusiasm for the movement towards the quantitative expression of geomorphic data, which became popular in the 1950s. He considered a preoccupation with numbers tended to stifle inspiration, and was sceptical of the so-called precision and objectivity of the 'new geomorphology'. Simple description was insufficient: he sought to define problems by examining actual landscapes, photographs, and maps, then rigorously tested his hypotheses against relevant geological data. He kept in touch with the latest international developments through his extensive reading and numerous contacts overseas. Cotton's ideas were invariably well presented, logically argued, and skilfully illustrated with explanatory diagrams.
Probably as a result of his rather lonely shipboard childhood, Cotton retained a shyness and reserve of manner throughout his career. This may account for his reluctance to accept official positions in scientific societies. He compensated by a willingness to devote time and attention to tasks such as editing or refereeing papers for publication, and reviewing published material. Similarly, he was not a lively lecturer and to younger students he could appear aloof, but senior students who had the chance to know him personally remember his warm interest in their welfare.
Cotton retired from Victoria in 1953. The following year he was made a professor emeritus and was awarded an honorary LLD. In 1959 he was knighted for his outstanding services to New Zealand geology. He continued to take an active role in research and publishing on geomorphology until shortly before his death, at Lower Hutt, on 29 June 1970. He was survived by his wife and children.
One of the leading scientists New Zealand has produced, Charles Cotton possessed a keen and logical mind and was capable of sustained concentration. He was one of the first geologists to appreciate the central importance of geomorphology. The key to his enduring influence as a teacher and populariser of geological studies was his careful but highly readable writing style, and his ability to illustrate with simple line drawings and diagrams the landforms that he studied and interpreted. He also possessed the drive for publication that is vital to the completion of worthwhile research. Although it may be said that Cotton's work did not create a school, nor even a formal following, through his writings New Zealand's geology became widely known throughout the scientific world. He made an outstanding contribution to our understanding of the evolution of New Zealand's landforms.