A trellis drainage pattern on folds. This resembles the trellis drainage pattern of eroded dipping sediment (slide Box XII-15), but opposing sets of tributaries are shorted and of more equal length than on cuesta topography. Strahler, 1960, p. 473.
Wandering the north magnetic pole through geologic time. although students of ancient rock magnetism regard this path as fairly well established, there is no conclusive proof that the geographic pole followed the same path or that the continents maintained their same positions during this lengthy period. Notice also that there are no signs of frigid conditions or glacial action in northeastern Asia during the periods when the pole was supposed to be in that vicinity. Stokes, 1960, p. 168.
Earthquake epicentres (black dots and circles) in the middle of the Atlantic almost fall within a narrow belt that coincides with rift valley of the mid-Atlantic Ridge. Open circles indicate strongest earthquakes; solid dots represent weaker earthquakes. Heezen, 1960.
Confined and unconfined aquifers. Artesian wells may be flowing or non-flowing depending on whether the pressure surface is above or below the ground surface. (A) Wells in an unconfined aquifer. (B) Artesian wells in a confined artesian aquifer. Zumberge, 1958, p. 135.
Angular unconformity. Zechstein above folded Carbiniferous. Carboniferous rocks (folded intensely) were leveled down by erosion; and on the erosion surface Permian strata (Zechstein) were horizontally deposited. The whole sequence was then raised, and again attacked by erosion. Cloos, 1954, p1. 44.
Wave refraction. The manner in which waves are refracted on an irregular shoreline. It is assumed that the water is deeper off the bay off the headlands. Consider that the original wabe is divided into three equal segments A-B, B-C, and C-D. Each segment has the same potential energy. But observe that by the time the wave reaches the shore the energy of A-B and C-D has concentrated along the short shoreline of headlands A'-B' and C'-D', while the energy of B-C has been dispersed over a greater front (B'-C') around the bay. Thus there is more energy available for erosion per unit of shoreline on the headlands than there is along the bay. Leet and Judson, 1958, p. 310.
