A Method for Measuring the Movement of Rocks and Glaciers with Simple Equipment

Abstract

Contains explanation of the Van Heel method of precision alignment. Equipment consists of three marks placed in a line: (1)single slit illuminated by a projection lamp, (2) double slit placed between the first slit and the eyepiece, and (3) eyepiece. Light originating at the first slit undergoes diffraction at the second, resulting in an interference pattern observed with the eyepiece. Outer two marks may be mounted in solid rock, the center mark on moving rock or glacier. Marks may be left in the field.