The Secret Land is a 1948 documentary feature produced by Orville O. Dull.
It is a record of Operation Highjump, a massive U.S. Navy expedition to Antarctica in 1946-47. The expedition, led by famed polar explorer Richard E. Byrd, brought 13 ships and 4700 men to the Antarctic, in three separate squadrons, devoted to exploring and surveying three different areas of the continent. The fleet battles the myriad difficulties of the Antarctic environment, including the high winds of the interior, but worst of all the massive ice floes that threaten to crush Byrd's ships. Tragedy also strikes when a plane on a surveying mission disappears in bad weather.
Three different narrators—Robert Montgomery, Robert Taylor, and Van Heflin—narrate each of the three prongs of the expedition. In Real Life Operation Highjump has attracted a lot of interest from the Tinfoil Hat brigade, with a lot of loopy theories about a Nazi base at the South Pole.
- Dramatization: "For brevity, the sequence of events has occasionally been rearranged." Parts dramatized after the fact include an amazingly awkward, wooden conference between Byrd and Admiral Chester Nimitz, some damage control efforts aboard the ships, and Byrd's difficult flight to the Pole and back (including the Emergency Cargo Dump).
- Emergency Cargo Dump: Admiral Byrd's plane loses one of its two engines on the way back to from the South Pole. As a consequence the plane starts rapidly losing altitude. Byrd and his men have to chuck out everything except for their exposed film, and they barely manage to keep the plane in the air until they get back.
- Everything's Better with Penguins: They provide entertainment. One smallish penguin somehow flaps its way up onto a ship and stays there for two days. A flock of penguins leap out of the water and greet a ship. Sailors marvel at the amount of fish that emperor penguins eat.
- Hiroshima as a Unit of Measure: The area of the Antarctic interior that Byrd's planes photographed is said to be larger than California, Arizona, and Texas combined.
- Initiation Ceremony: The "shellback ceremony", in which "polliwogs" become shellbacks upon crossing the Equator for the first time. It involves much silliness, including kissing the belly of a fat sailor dressed up as King Neptune.
- Mysterious Antarctica: Mapping and photographing the Antarctic when much of it was still mysterious. The film documents the discovery of the Bunger Hills, an area strangely free of ice with bare hills and liquid lakes. The lack of ice in the Bunger Hills has never been scientifically explained.
- Nature Documentary: Antarctica, with its stark beauty and its lack of hospitality to man. Compare Encounters at the End of the World, a Werner Herzog documentary with a far different mood.
- Sea Stories: Most of the movie deals with the challenges of the naval vessels trying to make their way to the Antarctic coast and avoid being crushed in the ice.