Complex sentence: Mapped by Norwegian cartographers in 1957 from air photos taken by U.S. Navy Operation Highjump, 1946--47, and named for R. Admiral George J. Dufek, U.S. Navy, who had been commander of the Eastern Group of U.S. Navy Operation Highjump.
Split into simpler sentences: Mapped by Norwegian cartographers in 1957 from aerial photographs taken by United States Navy during Operation Highjump, 1946--1947. The nmountain was named for RADM George J. Dufek, who had been commander of the Eastern Group of Operation Highjump.