<P> Passive margins are often located in the interior of lithospheric plates, away from the plate boundaries, and lack major tectonic activity . They often face mid-ocean ridge s . The East Coast of the United States is an example of a passive margin . These margins are much wider and less sloped than active margins . </P> <P> As continental crust weathers and erodes, it degrades into mainly sands and clays . Many of these particles end up in streams and rivers that then dump into the ocean . Of all the sediment in the stream load, 80% is then trapped and dispersed on continental margins . While modern river sediment is often still preserved closer to shore, continental shelves show high levels of glacial and relict sediments, deposited when sea level was lower . Often found on passive margins are several kilometers of sediment, consisting of terrigenous and carbonate (biogenous) deposits . These sediment reservoirs are often useful in the study of paleoceanography and the original formation of ocean basins . These deposits are often not well preserved on active margin shelves due to tectonic activity . </P> <P> Economically, the continental shelf is the most economically valuable part of the ocean . It often is the most productive portion of the continental margin, as well as the most studied portion, due to its relatively shallow, accessible depths . </P> <P> Due to the rise of offshore drilling, mining and the limitations of fisheries off the continental shelf, the United Nations Convention on "Law of the Sea" was established . The edge of the continental margin is one criterion for the boundary of the internationally recognized claims to underwater resources by countries in the definition of the "continental shelf" by the United Nations Convention on the Law of the Sea (although in the UN definition the "legal continental shelf" may extend beyond the geomorphological continental shelf and vice versa). Such resources include fishing grounds, oil and gas accumulations, sand, gravel, and some heavy minerals in the shallower areas of the margin . Metallic minerals resources are thought to also be associated with certain active margins, and of great value . </P>

Which component of the continental margin has the greatest economic and political significance