fagasta and was largest in the bays from Coquimbo to Chafi- aral. It presented the usual character of these waves in that the sea first withdrew from the land, sinking away like an ebb- ing tide to a depth of many feet. The sea bottom was thus laid bare to a distance from the shore which varied with its slope. The sea then returned with three great waves which rose high- est at the ends of the funnel-shaped bays. At Coquimbo the first great wave reached an altitude of 8 meters and overturned railway locomotives. Across the bay, however, at La Serena, the height of the wave was about a meter and a half only. Since many of the ports along this part of the coast are located on low ground and at the ends of the bays, the damage done by the earthquake wave was considerable, but the destructive effect was nevertheless local.”
The West Zone of South America a Zone of Fracture and Displacement
The first law of earthquake distribution is that intensity and frequency of shock are in general greatest where the slope of the ground is greatest, that is where ocean deeps lie close to lofty mountains. There is no place in the world where this contrast is so great in a given horizontal distance as off the northern coast of Chile. The cross section, Figure 41, repre- sents the astonishingly abrupt transition from lofty table-land to abyssal ocean depth that is characteristic of the entire coast. It represents conditions along the coast of northern Chile in the vicinity of Taltal, where the Andes, attaining a height of over 16,000 to 18,000 feet (Mt. Llullaillaco, Figure 93, is over 20,000 feet high), fall off to the enormous depth below sea level of over 25,000 feet, a total descent of more than 40,000 feet in 175 miles, most of which (32,600 feet) is accomplished in 75 miles. From the northwestern coast of Peru southward to Concepción, in southern Chile, the 4000-metcr submarine con- tour is never more than 125 miles from the coast and generally less than half that distance away. We have here one of the great planes along which a major segment of the earth's crust is undergoing adjustment; the line of movement being often-
