GEOMAGNETIC OBSERVATIONS ON MARION ISLAND, GOUGH ISLAND AND TRISTAN DA CUNHA

Abstract

In September 1957 the International Association of Geomagnetism and Aeronomy recommended that a magnetic secular variation station be established on Tristan da Cunha (37°03' S., 12°18' W.). During the ensuing three years the Union of South Africa has established secular variation stations on no fewer than three of the southern islands, viz. Tristan da Cunha, Gough Island (40°20' S., 9°55' W.), and Marion Island (46°51' S., 37°52' E.). As all three islands are composed of highly magnetic material, it is essential that the points at which the initial observations were made be exactly reoccupied during future surveys. The stations (two on each island) were accordingly clearly marked, and a careful record was kept of the height above ground-level at which each observation was made. The results of the magnetic observations carried out on the three islands in 1960 are presented in full. It is recommended that the stations be reoccupied at intervals of about five years.