. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 808 THE EEGOLITH composed of an indiscriminate admixture of particles of all sizes, from those as fine as dust to blocks it may be of hundreds of tons' weight Such are necessarily limited to the immediate vicinity of the cliffs or mountains from which they are derived. As loosened by heat or frost from the parent masses, the frag- ments tumble down the slopes, gradually accumulating in beds the inclination of which is limited only by the laws of 'â â¢^ gravity and the character of the debris (See PL 25.) â¢; Inclinations of 3
. A treatise on rocks, rock-weathering and soils;. Petrology; Soils. 808 THE EEGOLITH composed of an indiscriminate admixture of particles of all sizes, from those as fine as dust to blocks it may be of hundreds of tons' weight Such are necessarily limited to the immediate vicinity of the cliffs or mountains from which they are derived. As loosened by heat or frost from the parent masses, the frag- ments tumble down the slopes, gradually accumulating in beds the inclination of which is limited only by the laws of 'â â¢^ gravity and the character of the debris (See PL 25.) â¢; Inclinations of 30° are common. From their ""^-- mode of origin it is natural that the individ- \ ual particles should be mainly angular and \ comparatively fresh. In fact, they represent \ rock-weathering through disintegration, and not decomposition, which will come later. Above, they consist simply of masses of loose rock wholly unfitted for the support of vegetable life; below, they pass gradu-. Soil hearing pc^ti/oru ^afXless partftaiv Fig. 31. â Diagram showing the history of a talus, a, bed rock; hh, talus; c, de- stroyed portion of a eliff, the material being now in the talus. ally into soils. (Fig. 31.) Through becoming saturated with water, ice, or snow, such at times become loosened from the steep slopes on which they lie and slide down in the form of avalanches into the valleys. (PL 27.) Although comparatively limited in their extent, these latter, owing to the resistless energy and suddenness of their advance, are sometimes appall- ingly destructive, as has been repeatedly illustrated in mountain regions the world over. The geographic distribution of talus deposits as controlled by climatic conditions has been already noted, (2) Alluvial Deposits. â The deposits included under this head differ structurally from those thus far described in that they are always more or less distinctly stratified, or bedded. In writing of the formation of sedimentary rocks, and aga
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectpetrolo, bookyear1913
