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We document the discovery of an active, shallow, seafloor hydrothermal system (known as the Seven Sisters Vent Field) hosted in mafic volcaniclasts at a mid-ocean ridge setting. The vent field is located at the southern part of the Arctic mid-ocean ridge where it lies on top of a flat-topped volcano at ~130 m depth. Up to 200 &deg, C phase-separating fluids vent from summit depressions in the volcano, and from pinnacle-like edifices on top of large hydrothermal mounds. The hydrothermal mineralization at Seven Sisters manifests as a replacement of mafic volcaniclasts, as direct intraclast precipitation from the hydrothermal fluid, and as elemental sulfur deposition within orifices. Barite is ubiquitous, and is sequentially replaced by pyrite, which is the first sulfide to form, followed by Zn-Cu-Pb-Ag bearing sulfides, sulfosalts, and silica. The mineralized rocks at Seven Sisters contain highly anomalous concentrations of &lsquo, epithermal suite&rsquo, elements such as Tl, As, Sb and Hg, with secondary alteration assemblages including silica and dickite. Vent fluids have a pH of ~5 and are Ba and metal depleted. Relatively high dissolved Si (~7.6 mmol/L Si) combined with low (0.2&ndash, 0.4) Fe/Mn suggest high-temperature reactions at ~150 bar. A 13C value of &minus, 5.4&permil, in CO2 dominated fluids denotes magmatic degassing from a relatively undegassed reservoir. Furthermore, low CH4 and H2 (&lt, 0.026 mmol/kg and &lt, 0.009 mmol/kg, respectively) and 3He/4He of ~8.3 R/Racorr support a MORB-like, sediment-free fluid signature from an upper mantle source. Sulfide and secondary alteration mineralogy, fluid and gas chemistry, as well as 34S and 87Sr/86Sr values in barite and pyrite indicate that mineralization at Seven Sisters is sustained by the input of magmatic fluids with minimal seawater contribution. 226Ra/Ba radiometric dating of the barite suggests that this hydrothermal system has been active for at least 4670 &plusmn, 60 yr.

A 2003 high-resolution magnetic survey conducted by the Autonomous Underwater Vehicle ABE over the low-temperature, ultramafic-hosted hydrothermal field Lost City reveals a weak positive magnetic anomaly. This observation is in direct contrast to recent observations of strong positive magnetic anomalies documented over the high-temperature ultramafic-hosted hydrothermal vents fields Rainbow and Ashadze, which indicates that temperature may control the production of magnetization at these sites. The Lost City survey provides a unique opportunity to study a field that is, to date, one of a kind, and is an end member of ultramafic-hosted hydrothermal systems. Our results highlight the key contribution of temperature on magnetite production resulting from serpentinization reactions. Whereas high temperature promotes significant production and partitioning of iron into magnetite, low temperature favors iron partitioning into various alteration phases, resulting in a magnetite-poor rock. Moreover, the distribution of magnetic anomalies confirms results of a previous geological survey indicating the progressive migration of hydrothermal activity upslope. These discoveries contribute to the results of 25 yrs of magnetic exploration of a wide range of hydrothermal sites, from low- to high-temperature and from basalt- to ultramafic-hosted, and thereby validate using high-resolution magnetics as a crucial parameter for locating and characterizing hydrothermal sites hosting unique chemosynthetic-based ecosystems and potentially mineral-rich deposits.

At frequently active submarine volcanoes, it is difficult to distinguish between new and pre-existing lava flows. A combination of high-resolution bathymetric surveys taken before and after an eruption at Axial Seamount in 2011 allows detailed mapping of the 2011 lava flows, and highlights the tendency of new flows to mimic older ones.

In an effort to explain the source of nonstorm streamflow in deep-soiled areas of the southern Appalachians, a 3×3× 45-foot inclining concrete trough was constructed on a 40 per cent slope. The structure was packed with a natural sandy-loam soil to a bulk density of 1.3, and after thorough soaking was covered with plastic to prevent evaporation. Outflow was measured at the base, and soil moisture tension and content were recorded for 145 days. As shown by piezometers, the larger pores were substantially emptied in 1.5 days, during which outflow occurred according to the expression, Q = a1T−b1 where T is time in days since day zero and a1 and b1 are constants. After a 5-day transition period, the logarithm of drainage for the next 80 days was again linearly related to the logarithm of time, but with new constants,a2 and b2, expressing unsaturated flow from the entire soil mass. An additional 60 days of flow occurred, deviating more and more from the log-log relation as the limits of drainage were approached. Soil moisture content and tension substantiated the theory that the entire unsaturated soil mass was contributing to outflow throughout the experiment. It is concluded that unsaturated flow in the earth mantle of steep watersheds cannot be ignored in hydrograph analysis, since it may well be a primary mechanism for sustaining baseflow.