Resurvey of Byrd Station, Antarctica, Drill Hole

The drill hole at Byrd Station, which was surveyed in January 1968 to a vertical depth of 7063 ft (2153 m) below the top of the casing, was resurveyed in January 1975 to a vertical depth of 4835 ft (1474 m). Inclination and azimuth measurements were made with a Parsons multiple-shot inclinometer wand compared with the earlier measurements made during drilling. The results indicate a progressively increasing displacement with depth to a value of 51.2 ft (15.6 m) at the 4835-ft (1474 -m) level, or about 7.3 ft/yr (2.23 m/yr). The direction of movement relative to the surface varies from southwest at 300 ft (91.5 m) to northeast at 1100 ft (335 m), to east at 3368 ft (1027 m), and to northeast at 4835 ft (1417 m), indicative of a complex twisting motion. An increase in accessible depth along the hole axis of 18 ft (5.49 m) beyond the 1969 depth was noted. No attempt was made to measure hole diameter or vertical strain. It is recommended that the hole be resurveyed in 3 to 5 years if it is still logistically feasible, using a better inclinometer.