Diagram Of Ocean Floor Features

October 30, 2022

Physical Geology

Important features are the vast continental shelves less than 250 m deep (pink); the vast deep ocean plains between 4,000 and 6,000 m depth (light blue and dark blue); the Mid-Atlantic Ridge, in many areas less than 3,000 m deep; and the deep ocean trench north of Puerto Rico (8,600 m). The bottom of the Pacific, like those of other oceans, is actually very flat, even in areas of seamounts or deep trenches. The main features of the Pacific Ocean floor are continental slopes, which drop from about 200 m to several thousand meters over a distance of a few hundred kilometres; abyssal plains — extremely flat and 4,000 m to 6,000 m deep; seamounts and volcanic islands; and trenches in subduction zones down to 11,000 m depth. The ocean floor rests almost entirely on mafic oceanic crust (primarily basalt and gabbro, as described in more detail below), while the continental slopes rest on felsic continental crust (primarily granitic and sedimentary rocks). Continental shelves are generally less than 200 m deep; 200 m is also the limit of the photic zone, the maximum depth at which enough light penetrates to allow photosynthesis. The mesopelagic zone extends from 200 m to 1,000 m; the bathypelagic zone from 1,000 m to 4,000 m; and the abyssalpelagic zone is deeper than 4,000 m. (Pelagic refers to the open ocean and therefore excludes areas near the coasts or the ocean floor.) The deepest parts of the ocean are in subduction trenches, and the deepest of them it is the Mariana Trench in the southwest Pacific (near Guam) at 11,000 m (Figure 18.5).

Principles Of Earth Science

The topography of the North Atlantic Ocean is shown in Figure 14.2. Important features are the vast continental shelves less than 250 meters deep (pink); the vast deep ocean plains between 4,000 and 6,000 meters deep (light blue and dark blue); the Mid-Atlantic Ridge, in many areas less than 3,000 meters deep; and the deep ocean trench north of Puerto Rico (8,600 meters). The bottom of the Pacific, like those of other oceans, is actually very flat, even in areas of seamounts or deep trenches. The main features of the Pacific Ocean floor are the continental slopes, which drop from about 200 meters to several thousand meters over a distance of a few hundred kilometers, the abyssal plains - extremely flat and from 4,000 meters to 6,000 meters deep, volcanic seamounts and islands and trenches in subduction zones down to 11,000 meters deep. The ocean floor rests almost entirely on mafic oceanic crust (primarily basalt and gabbro, as described in more detail below), while the continental slopes rest on felsic continental crust (primarily granitic and sedimentary rocks). The continental shelf and slope off Nova Scotia is shown in Figure 14.4. In this passive margin zone (no subduction zone), the plateau is more than 150 kilometers wide. Continental shelves are generally less than 200 meters deep; 200 meters is also the limit of the photic zone, the maximum depth at which enough light penetrates to allow photosynthesis. The mesopelagic zone extends from 200 meters to 1,000 meters, the bathypelagic zone from 1,000 meters to 4,000 meters and the abyssalpelagic zone is deeper than 4,000 meters. Although the temperature of the ocean surface varies widely - from a few degrees either side of freezing in the polar regions to over 25°C in the tropics - in most parts of the ocean , the water temperature is about 10°C at 1,000 meters depth and about 4°C from 2,000 meters depth to the bottom. The deepest parts of the ocean are in the subduction trenches, and the deepest of these is the Mariana Trench in the southwest Pacific (near Guam) at 11,000 meters (Figure 14.5). There are other trenches in the Pacific Southwest more than 10,000 meters deep; the Japan Trench is more than 9,000 meters deep; and the Puerto Rico and Chile-Peru trenches are over 8,000 meters deep.

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Ocean-Floor Bathymetry

Certain features, such as mid-ocean ridges (where oceanic crust is constantly being produced) and subduction zones, also known as sea trenches (where it is constantly being destroyed), are unique to the ocean floor. The hypsographic curve The elevation features of the ocean floor - shelves, slopes, elevations, plains, ridges and trenches - are quantitatively summarized by oceanographers, along with the distribution of dry land at different elevations, in a graph called the hypsographic curve (see figure).