Trenches, ocean

You have been asked to prepare an outline design for the pressure hull of a deep-sea submersible vehicle capable of descending to the bottom of the Mariana Trench in the Pacific Ocean. The external pressure at this depth is approximately 100 MPa, and the design pressure is to be taken as 200 MPa. The pressure hull is to have the form of a thin-walled sphere with a specified radius r of 1 m and a uniform thickness t. The sphere can fail in one of two ways ... 

About 80% of the earth s surface is covered with aqueous solution. This liquid layer, the oceans, is called the hydrosphere. The average depth of the hydrosphere is about three miles but at ocean deeps or trenches, it changes precipitously to depths over twice that. 

Fujioka, K. (1987) Volcanogenic sediments of the Japan trench area and Tertiary explosive volcanism of the Tohoku arc. In Nasu, N. et al. (eds.). Formation of Active Ocean Margins, D. Reidel Publ., pp. 423-442. 

Masuda, F. (1984) Sedimentary basins in arc-trench system as a high-sensitive recorder of oceanic plate motion. Mining Geology, 34, 1-20 (in Japanese). 

Fig. 3.3. Marginal basins around the Pacific Ocean. Solid areas show marginal basins, and blocked lines show trenches. E East, N North, S South. W West (Tamaki and Honza, 1991).

Methanogens, may be the Earth s oldest organisms, produce methane from carbon dioxide and hydrogen. They can survive only in an anaerobic (i.e., oxygen-free) environment and have been found in ocean trenches, in mud, in sewage, and in cow s stomachs. 

The distribution of sediment types in the Pacific Ocean is much different from that of the Atlantic. Except for the coastline of the northwest United States, the Pacific is ringed by deep-sea trenches and, hence, has relatively narrow continental shelves. The trenches effectively trap all the terrigenous particles carried to the sea by river runoff. The Pacific Ocean is much wider than the other oceans thus the flux of wind-borne lithogenous particles is spread over a much greater area and produces a much lower mass flux, on an areal basis, to the seafloor. This makes other particles relatively important in determining the composition of the sediments in the Pacific ocean. 

Pressure effects on equilibria in liquids or solids are generally less spectacular than temperature effects, at least at the pressures normally encountered in chemical engineering (a few tens of megapascals) or in the environment (hydrostatic pressures in the ocean trenches exceed 100 MPa, but about 40 MPa would be more typical of the ocean floors). Higher lithostatic pressures are, of course, found beneath the Earth s surface, reaching 370 GPa (0.37... 

Between 1946-1970, approximately 28,000 fifty five-gallon drums of military and commercial low-level waste were disposed of in the Atlantic Ocean and approximately 47,000 in the Pacific ( ). This practice was discontinued in 1970 and since then all low-level waste has been buried in shallow trenches. 

The Deep Sea Drilling Project (DSDP), currently the Integrated Ocean Drilling Program (IODP) of the National Science Foundation, has undertaken the most systematic evaluation of ocean hydrate deposits. The DSDP has recovered hydrate cores in the deep oceans from both coasts of the United States, from the Mid-America Trench off Guatemala, and off the coast of Peru. Atotal of 23 oceanic hydrate cores have been recovered, including the Gulf of Mexico and three Soviet... 

October 19,1988), in addition to biogenic dominance in ocean hydrates (Dillon and Max, 2000), with sporadic mixtures of biogenic and thermogenic gas in Alaska, Russia, offshore Canada, and the Gulf of Mexico. It is possible to have both means (in place generation and fast fluxes) of supplying biogenic gas, indicated by Kvenvolden et al. (1984) and Kvenvolden and Claypool (1985) at DSDP Site 570 in the Middle America Trench. 

Water refers to the release of chemicals into rivers, lakes, streams, oceans, and other bodies of surface water from all discharge points at the facility This category includes the release from on-site waste-water treatment systems, open trenches, and stormwater runoff. 

There are several types of environments on Earth where significant water exists at prevalent low temperatures such that ice and liquid aqueous solutions commonly coexist permafrost, snow, glaciers, lake and river ice, sea ice, and parts of the atmosphere (polar troposphere, global upper troposphere, and stratosphere). In addition, the deep sea floor occurs at temperatures very close to the freezing point of water. For example, temperatures in the oceanic abysses hover around 2°C at a maximum hydrostatic pressure of 1100 bars (10,660 m) in the Mariana Trench (Yayanos, 1995). Table 4.1 summarizes some of these environments. Furthermore, in some permafrost and sea-floor environments, the presence of nonpolar gases under pressure can stabilize a modified form of ice known as gas hydrates even where temperatures are not quite low enough for ordinary ice to form. 

Figure 4.4 Excess 3He profiles at various locations in the Pacific Ocean. NOVA (Kermadec trench) data from Clarke et al. (1969), GEOSECS data from Clarke et al. (1970), SCAN data from Craig et al. (1975). SCAN station 38 (6°30 S, 107°24 W) is at the crest of the East Pacific Rise nearby stations 35 and 41 are on opposite flanks. Reproduced from Craig et al. (1975).

Parameter Mid-Ocean Ridge and Oceanic Inlraplate Trailing Plate-Continental Margin Subduct) on (Trench) Continent- Continent Collision Rift Basins Intra-Plate (Craion)... 

Active margin a margin consisting of a continental shelf, a continental slope, and an oceanic trench. 

The suboxic zone is defined as the region between where oxygen decreases to near zero (O2 < 10 xM) and where sulfide first appears (H2S > 1 iM) [16, 17]. Many important redox reactions involving Fe, Mn, N, and other intermediate redox elements occur in the suboxic zone. Similar redox reactions take place in sediments throughout the world s oceans, but they are easier to study in the Black Sea because they are spread out over a depth scale of tens of meters (rather than centimeter or millimeter scales as in sediments). The Black Sea suboxic layer hydrophysical structure is very stable compared with other ocean redox regions such as Cariaco Trench, which is influenced by mesoscale eddies, or the Baltic Sea that is influenced by inflows of the North Sea saline oxygenated waters in cold winters. 

Although soil microbes have been studied for decades, fundamental biological questions still remain unanswered. As stated by Noah Fierer of the University of Colorado We probably know more about the organisms in the deepest ocean trenches than we know about the organisms living in our soil in our backyard ... 

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