Continent

Continents consist of large blocks of continental crust, evidenced by dry land, bordered by continental shelves—the part of the continental crust that is below sea level. Every continent is also surrounded by either passive or active continental margins. At a passive margin, the continental shelf is typically a broad, nearly flat, sediment-covered submarine platform which ends at a water depth of about 600 ft (180 m) and tens or hundreds of miles (tens or hundreds of km) offshore. Marked by an abrupt increase in slope, known as the shelf break, the true edge of the continent is hidden below a thick layer of sediments on the adjacent continental slope. Seaward of the continental slope, a thick sediment wedge forms a much lower angle surface, called the continental rise. These sediments generally rest on oceanic crust, not continental crust. However, both the felsic crust of the continental margin and the mafic crust of the ocean floor are part of the same tectonic plate.

At active continental margins, interactions between two or more plates result in a very abrupt boundary between one plate's continental crust, and the crust of the neighboring plate. Typically, the continental shelf is narrow. For example, off the coast of Washington State, the Juan de Fuca plate subducts below the North American plate and the profile of the coast is very steep. There is no continental slope or rise because sediments move from the shelf down into the nearby ocean trench.