Core Drilling Through the Antarctic Ice Sheet

The Antarctic ice sheet was penetrated by core drilling at Byrd Station (80° 01´S, 119° 32´W) during the 1967-68 austral summer. The drill was a cable-suspended electro-mechanical rotary type 87 ft long, weighing 2650 lb. An electrohydraulic hoist raised and lowered the drill at a maximum rate of 150 ft/min. Other equipment included 12,000 ft of armored electrical cable and 70-ft-high aluminum tower. During the 1966-67 austral summer, the equipment was installed and a depth of 745 ft was drilled. Drilling resumed in November 1967 and the hole was completed in January 1968. Cores 10 to 20 ft long averaging 4 ¼ in. diam were recovered over 99% of the depth. The penetration rate averaged 70 ft/day. The drilling rate varied from 1.4 to 7.8 in./min at a power input of 7.5 to 9 kw. Drill cuttings were dissolved in an aqueous ethylene glycol solution circulated at the bottom of the hole and returned to the surface in the drill bailer on each coring run. Liquid water, indicative of pressure melting at the bottom of the ice sheet, was encountered at 7101 ft. Attempts to recover a core of sub-ice material were not successful. The hole began deviating from the vertical at 750-ft depth, and despite corrective measures, was inclined 15 degrees at the bottom. Ice temperatures increased steadily from a minimum of -28.8 degrees C at 2400 ft to -13.0 degrees C at 5942 ft, where temperature measurement ceased. The heat flow for this location is estimated to be 1.8 pcal/cm2 sec.