THE ORIGIN AND THE FORMS OF MOUNTAINS A mountain defined—The festoons of mountain arcs—Theories of origin of the mountain arcs—The Atlantic and Pacific coasts contrasted—The block type of mountain—Mountains of outflow or upheap—Domed mountains of uplift; laccolites—Mountains carved from plateaus—The climatic conditions of the mountain sculpture—The effect of the resistant stratum—The mark of the rift in the eroded mountains—Reading references 435 APPENDICES A. The quick determination of the common minerals 449 B. Short descriptions of some common rocks 462 C. The preparation of topographical maps 467 D. Laboratory models for study in the interpretation of geological maps 472 E. Suggested itineraries for pilgrimages to study earth features 475 INDEX 489 LIST OF PLATES PLATE 1. Mount Balfour and the Balfour Glacier in the Selkirks _Frontispiece_ FACING PAGE 2. A. Layers compressed in experiments and showing the effect of a competent layer in the process of folding 44 B. Experimental production of a series of parallel thrusts within closely folded strata 44 C. Apparatus to illustrate shearing action within the overturned limb of a fold 44 3. A. An earthquake fault opened in Formosa in 1906 with vertical and lateral displacements combined 72 B. Earthquake faults opened in Alaska in 1889 on which vertical slices of the earth’s shell have undergone individual adjustments 72 4. A. Experimental tank to illustrate the earth movements which are manifested in earthquakes. The sections of the earth’s shell are here represented before adjustment has taken place 82 B. The same apparatus after a sudden adjustment 82 C. Model to illustrate a block displacement in rocks which are intersected by master joints 82 5. A. Once wooded region in China now reduced to desert through deforestation 156 B. “Bad Lands” in the Colorado Desert 156 6. A. Barren Karst landscape near the famous Adelsberg grottoes 188 B. Surface of a limestone ledge where joints have been widened through solution 188 7. A. Ranges of dunes upon the margin of the Colorado Desert 210 B. Sand dunes encroaching upon the oasis of Oued Souf, Algeria 210