Map indicating (in dotted areas) the extent of outcrops of Karroo formation (Upper Carboniferous to Jurassic) in South Africa and analogous continental formations in Equatorial Africa (Gignoux 1955, p. 242).
Two samples of quick clay showing startling contrast. Column of undisturbed clay (left) holds 11 kilograms (24 pounds). It can support 2,100 pounds per square foot surface. Another piece of the same clay pours like a liquid afer being stirred in a beaker. No water was added. Demonstration was made by Carl B. Crawford of the National Research Council of Canada (Kerr, P.F., 1963, Sci. Amer. Nov., p. 134).
Two types of slide shown schematically. At top three blocks of earth have rotated in clay-water slurry. In the other slide total liquefaction has occurred and water forced out of the clay has formed a pond. The vertical dimension is exaggerated five times. Typical slide has a figure-eight appearance. Material the leaves a hollow at the head region piles up at the foot. The low cliff at the neck is often the bank of a river (Kerr, P.F., 1963, Sci. Amer. Nov., p. 138).
Slide in Quebec on the Rimouski River was caused partly by the 14 degree slope (cross section at the top) much steeper than slopes usually associated with quick clay. A layer of soft, silty clay heavily charged with water formed a slip surface. The debris filled river for several thousand feet and created a temporary lake. Hummocky surface is typical of clay slide (Kerr, P.F., 1963, Sci. Amer. Nov., p. 138).
Collapse of quick clay is shown on microscopic scale in these schematic cross sections. Undisturbed clay (left) is thought to possess a "house of cards" structure. The "cards" are flat bits of clay minerals. Irregular blobs represent sand grains and tiny sots are dissolve salt, which provide electrolytic "glue" for the structure. Water (colour) is being squeezed out as clay collapses (middle). Most of the salt was leached out before collapse. Remolded or collapsed clay (right) contains very little water (Kerr, P.F., 1963, Sci. Amer. Nov., p. 134).
Map of southeastern part of Hawaii showing lava flows of the 1955 and 1960 eruptions of Kilauea. Letters indicate the location of the 1955 vents in the order of their outbreak (Bulman, 1962).
