Snow and ice
Glaciology, the study of snow and ice, encapsulates many aspects of the more conventional world of geology, including the study of igneous (lake, river, and sea ice), sedimentary (snow packs), and metamorphic (glaciers, ice sheets, and shelves) ice masses. However, glaciology avoids some of geology’s inherent problems because snow and ice bodies always occur on or near the surface of the earth and are, geologically speaking, quite thin: snow, lake, river, and sea ice are less than a few tens of meters; ice shelves and glaciers are less than a few hundred meters; and ice sheets are less than 4,000 m. Consequently, their investigation by either direct sampling (coring) or indirect geophysical methods is comparatively straightforward. They are also basically mono-mineralic; ice 1(h) and gas, plus in the case of sea ice, a liquid phase with minor amounts of a few simple solid salts. This is clearly a simplification when one considers the mineralogical complexities of most rock masses. Furthermore, color presents few problems, basic white on white.
In considering the differences between the behavior of natural ice masses and the more typical materials considered by engineering geologists, one must remember that ice on the Earth’s surface invariably exists at or near its melting temperature, as contrasted with surficial rock masses that occur at temperatures far below melting and are, relatively speaking, the real “frozen” bodies. From a research point of view, the “high” temperatures of natural ice masses are an advantage in that igneous, sedimentary, and metamorphic processes occur rapidly, resulting in changes that are invariably measurable in a few years and more commonly in a few hours or days; geologically near-lightning speeds.
Figures & Tables
A review of milestones and changes in geological theory and practice from which modern engineering geology in North America has developed. Five chapters discuss historical events and the contributions of early scientists and engineers; nine chapters review the state of knowledge of dominant geologic processes, phenomena, and specialized principles critical to modern practice; and three chapters discuss geologic environs and the properties of construction materials. Four chapters are devoted to geoscience investigations and related techniques for: initial regional-areal evaluation of conceptual candidate sites (Phase I); selection of preferred-designated sites and design (Phase II); typical kinds of investigations used during project construction (Phase III); and as-built documentation and explorations of the operating or rehabilitation phases. Closing chapters focus on the geoscientist's responsibilities relative to engineering failures, errors of judgment that impact works, litigation, and forensic geoscience. The 34 contributors present extensive case histories applicable worldwide.