Surface access passages to the original Amundsen-Scott South Pole Station were permanently exposed to drifting snow in early 1977 as a means of sealing off the abandoned facility from further visits.
Built in 1955-56 [sic] for the International Geophysical Year, the old station operated year-round through early January 1975. A replacement facility nearby was dedicated on 9 January 1975 (see March/April 1975 Antarctic Journal, pages 37-44).
The original U. S. station at the geographic South Pole bacame buried over the years under about 15 meters of snow and ice, the crushing weight of which eventually led to the decision to build the new station. After the new station opened, however, the old station was still visited from time to time to collect miscellaneous, small items that might be useful at the new station. Most salvageable items had already been removed from the old station at the time of its closing in early January 1975.
Occasional visitors to the old station reported hearing loud cracks, presumably caused by the weight of the snow and ice. Fearing that the strained buildings and tunnels might collaps, National Science Foundation officials declared the old station unsafe and ordered it sealed.
The above article appeared in the March/June 1977 issue of the Antarctic Journal.
A few comments...first let me say that in those days the actual mailing of the Antarctic Journal was frequently a number of months after the cover date. As for contemporary documentation, there was no formal direction received by the 1977 winter station management (yours truly) regarding the "sealing" of the station, and nothing was actually done to expose the entrances or allow them to get drifted up. Surprisingly, that actually would not take place until the 1984-85 summer--it was not until then that the remaining protruding structures (aurora tower, BIT platform above the galley) and escape hatches were made to disappear. As a result, in the late 1980's there was a definite visible rise in the landscape in the area of the old station as a result of the accumulated drifting...something I didn't really notice when I returned in 2005 and the area landscape had been transformed by the dark sector and its own associated drifting.