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Introduction to Offshore Operation
Published in Shashi Shekhar Prasad Singh, Jatin R. Agarwal, Nag Mani, Offshore Operations and Engineering, 2019
Shashi Shekhar Prasad Singh, Jatin R. Agarwal, Nag Mani
Oceans cover almost three-fourths of the earth’s surface, and the land beneath them can meet the energy requirements of the world for years to come. Beaches extend from the shore into the ocean on a continental shelf that gradually descends to a sharp drop called the continental slope. The continental shelf can be as narrow as 20 km or as wide as 400 km. Water on the continental shelf is usually shallow and rarely more than 150–200 m deep. Continental shelf drops off at the continental slope, ending in abyssal plains up to 3–5 km below the sea level. While many plains are flat, others have jagged mountain ridges, deep canyons, and valleys. The tops of some of these mountain ridges form islands where they extend above the water. Our borders extend 200 miles into the water from coastlines, encompassing areas larger than some countries. This large underwater area is called the exclusive economic zone (EEZ).
The United Nations Convention on the Law of the Sea and related agreements
Published in Mark Zacharias, Jeff Ardron, Marine Policy, 2019
The EEZ and a state’s continental shelf are not the same. The continental shelf is the submerged portion of a continent (seabed) that extends from the baseline to the 200nmi EEZ or until the submerged continent ends, whichever is greater. The LOSC refers to the ‘natural prolongation’ of the land territory as the ‘extended continental shelf’, including the seabed and subsoil of the shelf (Article 76). The LOSC provides two constraints on the maximum extents of the extended continental shelf: The first is that the shelf may not be more than 350nmi from a state’s coastal baselines. The second constraint limits the extended continental shelf 100nmi seaward from the 2,500 metre isobath (depth contour). Within the two above constraints, continental shelves can be delineated by the following means, also termed formula lines: Sediment thickness: A line, termed the Gardiner line, is defined by the points where the thickness of the sediment is at least 1 per cent of the distance to the foot of the slope.Bathymetry: A formula, termed the Hedberg formula, defines a line by points 60nmi seaward from the foot of the continental slope where the foot of the slope is defined as the point of maximum change in the gradient at its base. Once the Gardiner/Hedberg lines are established, then the constraint lines are applied to determine the outer limit of the continental shelf.
Nonrenewable Energy Resources
Published in Julie Kerr, Introduction to Energy and Climate, 2017
The ocean floor extends from the beach into the ocean on a continental shelf that gradually descends to a sharp drop, called the continental slope. The width of the U.S. continental shelf varies from 16 to 400 kilometers. The water on the continental shelf is relatively shallow, rarely more than 150 to 200 meters deep. The continental shelf drops off at the continental slope, ending in abyssal plains that are three to five kilometers below sea level. Many of the plains are flat, while others have jagged mountain ridges, deep canyons, and valleys. The tops of some of these mountain ridges form islands where they extend above the water.
Numerical modelling of the seismic response of gentle slopes in Southeastern Brazil
Published in Marine Georesources & Geotechnology, 2022
Cristian Yair Soriano Camelo, Maria Cascão Ferreira de Almeida, Marcio de Souza Soares de Almeida, Gopal S. P. Madabhushi, Brian Carlton
The offshore Campos Basin is situated in the southeastern continental margin of Brazil, off the coast of the states of Rio de Janeiro (RJ) and Espirito Santo (ES), and covers an area of approximately 100,000 km2 (Castro and Picolini 2016). A digital elevation model of the Campos Basin, presented in Figure 1, was developed with data from the General Bathymetric Chart of the Oceans (GEBCO Compilation Group 2020). The Campos Basin is in a passive margin tectonic context (de Almeida and Kowsmann 2016) and is divided into three physiographic provinces: continental shelf, continental slope, and São Paulo plateau (Figure 1). Different physical mechanisms are associated with the formation of those provinces. The continental shelf is the product of an interaction of sedimentary, hydrodynamic, and sea-level variation processes. The continental slope is the transition between the continental shelf and the São Paulo Plateau. Several geomorphologic features are present in the continental slope, such as submarine canyons and channels associated with mass wasting processes (Kowsmann et al. 2002) that took place in periods of relatively low sea level. Finally, the São Paulo Plateau is an area composed of an accumulation of muddy sediments from debris flows and contourites above the salt layer. Further details related to the geomorphology of the continental slope and the São Paulo Plateau can be found in de Almeida and Kowsmann (2016).
A hybrid method for electromagnetic scattering from target above composite rough surface of ground and near sea in adjacent region
Published in Electromagnetics, 2018
Gao Xiang Zou, Chuang Ming Tong, Hua Long Sun, Tong Wang, Peng Peng
According to the International Maritime Bureau, the water area whose depth is less than 600 m belongs to the near sea region. The water depth in the range of continental shelf is often less than 200 m. The slope of seabed is approximately ranging from 0 to 0.9. On the basis above, an approximate method is presented in Figure 2 to simulate the water depth in the range of continental shelf. This method is just a simple and approximate way to deal with the problem of water depth simulation. If we can obtain the datum of actual water depth in the range of near sea, the water depth simulation would be more accurate and reasonable.