Expedition of the research vessel "Vityaz" to the Pacific Ocean to study the Earth's mantle: seeing off the ship in the port of Vladivostok, the ship "Vityaz" in the ocean. The head of the expedition GB Udintsev tells the members of the expedition about the upcoming research. Members of the expedition, including foreign scientists, during research with the help of an echo sounder, seismic profiler. Blasting to obtain reflected waves. Meeting in the ocean of scientists of the research vessel "Vityaz" with the American research vessel "Maxi". Negotiations between the chiefs of the two expeditions. Meeting of Soviet and American scientists. Conducting collaborative research in the ocean. Crossing of the equator by the ship "Vityaz". A holiday on the ship. Photographing by members of the expedition of the ocean floor using a deep-sea photographic installation. Study of rocks raised from the bottom. Geological research on Norfolk Island, Philip Island, on the shores of New Zealand, on Lord Howe Island. Departure of the research vessel "Akademik Kurchatov" at sea for research in the Atlantic Ocean. "Akademik Kurchatov" off the coast of Iceland. The members of the expedition measure the Earth's magnetic field in the ocean, explore the rock raised from the ocean floor, and also carry out work to study the Icelandic rift zone, land on Jan Mayen Island.