Results taken from 270 publications on rates are summarized, and collated with those from 149 publications reriewed previously (Young, 1969(Young, ,1974. The data are classified by major climatic zone, normal or steep relief, and consolid ited or unconsolidated rocks. Representative rates and their ranges are given for soil creep, solifluction, surface wash, solution (chemical denudation), rock weathering, slope retreat, cliff (free face) retreat, marine cliff retreat, and denudation, the last being compared with representative rates of uplift. Solifluction is of the order of 10 times faster than soil creep, but both cause only very slow ground loss. Solution is an important cause of ground loss for siliceous rocks, on which it may be half as rapid as on limestones. Total denudation, brought about mainly by surface wash, reaches a maximum in the semi-arid and probably also the tropical savanna zones. Acceleration of natural erosion rates by human activities ranges from 2-3 times with moderately intense land use to about 10 times with intensive land use (and considerably higher still where there is recognized accelerated soil erosion). Where there is active uplift, typical rates are of the order of 10 times faster than denudation, although in some high, steep mountain ranges these may approach equality.

Quaternary sediments and landforms in Chilliwack River valley, southwestern British Columbia, provide a detailed record of déglaciation of this area between 12 000 and 11 000 years BP. Stratigraphic, sedimentological, and radiocarbon data show that a large glacier in eastern Fraser Lowland (part of the Cordilleran Ice Sheet) blocked the mouth of Chilliwack valley at a time when the middle reaches of the valley were ice free. A lake existed between the ice dam in the lower part of the valley and a delta – sandur complex, west of Chilliwack Lake, in the upper part of the valley. Two relatively minor advances of the Fraser Lowland ice lobe into lower Chilliwack valley occurred about 11 500 and 11 200 years BP. These were separated by a brief period of recession during which tephra was deposited and a coniferous forest and soil developed on freshly deglaciated terrain. Shortly after 11 200 years BP, a glacial lake formed in Cultus Lake basin; two sets of terraces in lower Chilliwack valley are graded to different levels of this lake. The glacier dam at the mouth of Chilliwack valley disappeared about 11 000 years BP, and déglaciation of Fraser Lowland was complete less than 100 years later.

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Recent physical climatology research from North American alpine tundra environments is summarized and directions for further research suggested. Despite a rather limited database, the essential themes in the physical climatology of alpine tundra are understood. With numerous permutations of slope angle, azimuth and surface types in the alpine zone, generalizations of alpine tundra radiation and energy balances are hard to define. Several aspects of the alpine tundra radiation budget are very similar to nonalpine ones, such as the controls exerted on net radiation by atmospheric and surface conditions, and the strong relation between global solar radiation and net radiation. The larger inputs of solar radiation experienced at high altitudes are typically offset by the moderating effects of orographic clouds. Turbulent energy flux partitioning is dependent upon both the effects of macroscale weather and microscale variations in surface soil moisture. Evaporation regimes tend to be moisture-limiting in the dry tundra and energy-limiting in wetter alpine/ subalpine meadows, but there are also significant season-to-season variations. Theory suggests that the surface heterogeneity common to the alpine zone must at times stimulate vigourous horizontal heat advection at a wide range of spatial scales, but the true significance of this process remains almost entirely undocumented. Suggested future research directions include analyses of the spatial variations of albedo, the role of sloping surfaces, and the relative importance of atmospheric and surface controls on the energy balance.