Theory question 205
Oceans and Lakes(a) Draw a diagram to show the relief features of an ocean floor. (b) Highlight three main characteristics of the continental shelf. (c) In what three ways is the continental shelf of importance to man?
Show the model answer
(a) Cross-section from the coast: continental shelf (gentle slope to about 180-200 m), continental slope (steep), continental rise, deep-sea (abyssal) plain with oceanic ridges, seamounts/volcanic islands and ocean deeps/trenches; label each.
(b) Gently sloping margin of the continent; shallow water, usually less than 200 m deep; width varies from a few km to hundreds of km; covered with sediments from the land; sunlight reaches the bottom.
(c) Rich fishing grounds (plankton growth); source of petroleum, gas and other minerals; good for harbours and ports; recreation and tourism; sand and gravel for construction.
Label shelf, slope, plain, ridge and trench on the diagram.