A. M. Sagalevich , P. V. Torokhov , V. V. Matveyenkov , S. V. Galkin & L. I. Moskalev To cite this article: A. M. Sagalevich , P. V. Torokhov , V. V. Matveyenkov , S. V. Galkin & L. I.From: "Gidrotermal'nyye proyavleniya podvodnogo vulkana Piypa (Beringovo more)," Izvestiya Akademii Nauk, seriya geologicheskaya, 1992, No. 9,pp.l04-114. The shallow depth of the hydrothermal vents on Piyp Volcano, which rises to a depth of 352 m, is responsible for some unusual features, both mineralogical and biological. The hydrothermal edifices are composed of anhydrite, calcite and barite, rather than sulfides, and gas bubbles discharged with the fluids contain mostly methane. Bacterial mats cover much of the surface in the vicinity of the vents. Piyp is the northernmost locality for Calyptogena, the characteristic mollusk of hydrothermal vent fauna.Piyp Submarine Volcano lies at the tip of the Vulkanolog massif in the western part of the Bering Sea. The volcano was discovered in 1984, and later examined in detail*on cruises of the R/V Vulkanolog [3]. The volcanic edifice rises more than 4000 m above the floor of a basin that marks a major north-south trending graben. The massif and graben are youthful structures that have developed as a result of back-arc spreading [4]. In 1987, a plume of bubbles was recorded on the echo sounder in the water above the summit of the volcano.The first part of the 22nd cruise of R/V Akademik Mstislav Keldysh, in the summer of 1990, was devoted to a study of the earlier-discovered hydrothermal activity on this volcano. Four dives on the volcano with a Mir manned submersible and several dredge hauls were made, which enable us to make a comparatively detailed report on the geological structure, the nature of the hydrothermal activity, and the distribution and composition of the benthic biota.Piyp Volcano has two clearly-defined summits (North and South), probably of different ages. The summits are separated by a saddle with maximum depths reaching 820 m. Hydrothermal activity was observed from the Mir submersible on both North and South summits. Each summit has its own specific features; therefore it seems appropriate to describe them separately.
North SummitDetailed echo-sounder measurements on the R/V Vulkanolog indicate that North Summit has two independent domes (western and eastern), within the 400-m isobath (Fig. 1). The western slope of the volcano is covered with dacite blocks above a depth of 700 m. The size of the blocks gradually increases upward and the western dome, lying at a depth of 360 m, consists of massive dacite broken by fissures into large rectangular blocks, sometimes creating the appearance of a 1200
