Particle sorting and stone migration due to frost heave.

33°N, long. 127°W, about 650 km west of Los Angeles. These holes will be drilled to about 300 meters, the depth depending on the maximum which can be attained with one bit because hole reentry will not be feasible. The drilling will test the hypothesis of ocean floor spreading (1) and the generation of long, linear, magnetic anomalies according to the Vine-Matthews hypothesis (2), relating them to spreading coupled with reversals of the earth's magnetic field. The main factual information to be sought will be (i) the age of the oldest sediments lying upon the harder rock of layer 2 of the oceanic crust; (ii) the age of the top of layer 2, presumably basalt, by radiometric age determination; and (iii) whether, on magnetic positive and magnetic negative residual anomalies, the remanent magnetization of the rock is normal and reversed, respectively. The tentative geographic positions of the holes with respect to the magnetic anomalies are shown in Fig. 1. The data used in compiling it come from magnetic surveys (3) and from Menard's physiographic diagram of the area (4). H. H. HESS Department of Geology, Princeton University, Princeton, New Jersey H. S. LADD U.S. Geological Survey, Washington, D.C.