[1] The first probabilistic tsunami flooding maps have been developed. The methodology, called probabilistic tsunami hazard assessment (PTHA), integrates tsunami inundation modeling with methods of probabilistic seismic hazard assessment (PSHA). Application of the methodology to Seaside, Oregon, has yielded estimates of the spatial distribution of 100-and 500-year maximum tsunami amplitudes, i.e., amplitudes with 1% and 0.2% annual probability of exceedance. The 100-year tsunami is generated most frequently by far-field sources in the Alaska-Aleutian Subduction Zone and is characterized by maximum amplitudes that do not exceed 4m,with an inland extent of less than 500 m. In contrast, the 500-year tsunami is dominated by local sources in the Cascadia Subduction Zone and is characterized by maximum amplitudes in excess of 10 mand an inland extent of more than 1k m. The primary sources of uncertainty in these results include those associated with interevent time estimates, modeling of background sea level, and accounting for temporal changes in bathymetry and topography.N onetheless, PTHA represents an important contribution to tsunami hazard assessment techniques; viewed in the broader context of risk analysis, PTHA provides amethod for quantifying estimates of the likelihood and severity of the tsunami hazard, which can then be combined with vulnerability and exposure to yield estimates of tsunami risk.

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Three active hydrothermal vents forming sulfide mounds and chimneys (Monolith, Fountain, and Pipe Organ) and more widely distributed inactive chimneys are spatially related to a system of discontinuous fissures and young sheet flow lavas at the northern Cleft segment, Juan de Fuca Ridge. The formation of zoned tubular Curich chimneys (type I) on the Monolith sulfide mound is related to focused flow of high‐temperature (to 328°C) fluid. Bulbous chimneys (type II or “beehives”) at the Monolith and Fountain vents are products of diffuse high‐temperature (to 315°C) discharge. A broader zone of vigorous mixing between the hydrothermal fluid and seawater results in quench crystallization of anhydrite‐rich shells. Columnar Zn‐sulfide‐rich chimneys with narrow channelways (type III) are constructed where focused and relatively low‐temperature (261°C) fluid vents directly from the basalt substrate. The bulk chemistry (low Cu; high Pb, Ag, and SiO2 contents), mineralogy (pyrite‐marcasite‐wurtzite‐amorphous silica‐anglesite), colloform and filamentous textures, and oxygen isotope characteristics of inactive (type IV) chimneys indicate a low‐temperature (<250°C) origin involving diffuse and sluggish flow patterns and conductive cooling. Seafloor observations and 210Pb data indicate that (1) type IV chimneys are products of an earlier period of hydrothermal activity that ended no more than 60 years ago but prior to the sheet flow eruption, (2) the high‐temperature Monolith and Fountain vents are manifestations of the same heating event (shallow emplacement of magma) that led to the sheet flow eruption and recent megaplumes, and (3) the Pipe Organ Vent is in a very youthful stage of development and chimney deposition postdates the sheet flow eruption.

Submarine landslides can be important mechanisms for transporting sediment down sloping seabeds. They occur when stresses acting downslope exceed the available strength of the seabed sediments. Landslides occur preferentially in particular environments, including fjords, active river deltas, submarine canyons, volcanic islands and, to a lesser extent, the open continental slope. Evaluating the relative stability of different seabeds requires an understanding of driving stresses and sediment strength. Stresses can be caused by gravity, earthquakes and storm waves. Resisting strength can be reduced by pore water and gas pressures, groundwater seepage, rapid sediment deposition, cyclic loading and human activity. Once slopes have become unstable or have failed, strength may continue to decrease, leading to sediment debris flows and possibly turbidity currents. Recent submarine landslide research has: shown that landslides and sediment waves may generate similar deposits, which require careful interpretation; expanded our knowledge of how strength develops in marine sediment; improved techniques for predicting sediment rheology; and developed methodologies for mapping and predicting the medium-to large-scale regional occurrence of submarine landslides.

Mesozooplankton (>200 μm) collected in August and September of 2010 from the northern Gulf of Mexico show evidence of exposure to polycyclic aromatic hydrocarbons (PAHs). Multivariate statistical analysis revealed that distributions of PAHs extracted from mesozooplankton were related to the oil released from the ruptured British Petroleum Macondo‐1 (M‐1) well associated with the R/VDeepwater Horizon blowout. Mesozooplankton contained 0.03–97.9 ng g−1 of total PAHs and ratios of fluoranthene to fluoranthene + pyrene less than 0.44, indicating a liquid fossil fuel source. The distribution of PAHs isolated from mesozooplankton extracted in this study shows that the 2010 Deepwater Horizon spill may have contributed to contamination in the northern Gulf of Mexico ecosystem.