It has recently been recognized that, in addition to low concentrations of widespread natural gas hydrate associated with bottomsimulating seismic refl ectors, highly concentrated hydrate can occur in local seafl oor fl uid venting structures. Such structures extend upward into the regional gas hydrate stability fi eld and sometimes allow gases to escape into the overlying ocean. These hydrate-choked chimneys are especially prospective as an energy resource because they contain high hydrate concentrations. Furthermore, they may be one of the most important conduits into the ocean-atmosphere system for deep methane. We present an analysis of two-dimensional seismic refl ection data from offshore Korea that give a complete picture of gas migrating from a deep source zone to feed hydrate-choked vent structures at the seafl oor. The gases migrate upward through networks of fractures imaged as steep amplitude striations in both diffuse and concentrated distributions. We present an example of a high-fl ux gas vent fed through fracture swarms emanating from a 10-15-km-wide catchment zone of source gases residing 3-4 km below the seabed. The geological context and the inferred distribution of hydrate within this feature are consistent with recent models in which seabed gas venting is a consequence of elevated pore fl uid salinities that are produced by a high fl ux of gases migrating independently of the pore water. In contrast, a nearby vent that is not plumbed into the same high-fl ux system appears to be dominated more by gas-rich liquids. We present these two vent structures as type cases for high-and lowfl ux fl uid escape systems in the seabed. Furthermore, we suggest that since the amount of gas trapped as hydrate within the vents is small compared with the amount in the underlying reservoir, the greatest risk for increased methane input to the atmosphere associated with climate-driven oceanic warming is not the melting of hydrate, but an increase in the number of deep reservoirs able to vent gases through the seabed that occurs as the regional gas hydrate stability zone thins.

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Geologic structure around holes drilled during Ocean Drilling Program Leg 139 is interpreted from single-and multichannel seismic reflection data. The holes are in a fault block of a sedimented rift valley (Middle Valley) of the Juan de Fuca ridge. This block is bound by two west-facing normal faults that separate crustal blocks with significantly different sedimentary sequences. Sediments in the drilled block are 200 to 500 ms thick and are underlain by nearly flat, high-amplitude reflectors. These events are 500-1000 m in width and appear to step down to the west towards younger crust. The events are interpreted to be the top of a sediment-sill complex that formed during simultaneous volcanism, extension, and sedimentation. Four groups of these bright reflectors can be correlated along strike in the fault block. Because they are elongated along strike, we infer that they are sills that were intruded as magma welled up along extensional faults. Several previously unmapped west-facing normal faults have been interpreted on the west side of the fault block; their offsets increase with depth and range from 10 to 100 ms. Contrary to a previous interpretation, we show that the character of sediments and basement across the eastern block-bounding fault near Site 855 is different and that this fault has been active for some time. Site 856 and another hydrothermal mound to the north are associated with shallow basalt reflectors significantly smaller in their lateral extent than the elongated sills within the fault block. Sites 857 and 858 are near the western block-bounding fault; Holes 857A and 857C are separated by a small offset fault. A region no more than 2 km along strike around Site 858 appears to have been uplifted by tens of meters. This uplift is presumably related to late-stage igneous activity documented by drilling.

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A large number of solar cells is metallized by printing and firing glass containing silver pastes. However, the contact formation is not fully understood so far. There is still a lack of understanding the role of the glass phase in the complex contact formation scenario because single effects could not been seperatly observed and evaluated up to now. To overcome this, an in-situ method to observe the contact formation via a contact resistance measurement was introduced. A special measuring device was applied to characterize two typical front side pastes, featuring a PbO-containing as well as a PbO-free glass frit during firing. The viscosity of the paste glass showed decisive influence for the etching of the anti-reflection coating (ARC). The ARC was opened immediately after entering the softening range of the respective glass, regardless of large differences in glass chemistry. Furthermore, the viscosity-temperature behaviour of the paste glass determines the intensity of the redox-reaction and related silver precipitation at the interface, which takes part between ARC opening and glass resolidification. The cooling slope was confirmed to have decisive influence on the final interface conductivity, because a crucial part of silver colloids can be formed here