ABSTRACT
The expression the ‘continental shelf’ is used both by geographers and lawyers and it is important to be clear as to exactly what is being referred to. It is therefore sensible to consider first the use made of the expression by physical geographers. If one considers the seabed adjacent to a coast then, in many instances, it can be observed that there are three distinct sections before the bed of the ocean is reached. Immediately adjacent to the coast, the seabed will gradually slope down from the low water mark to a point of about 130 metres in depth: this is the continental shelf in the sense used by a physical geographer. At or about that point, the angle of declination is observed to increase (that is, the slope becomes much steeper) and this will continue to a point between 1,200 and 3,500 metres in depth; this second section, having the steeper slope, is known as the continental slope. Thirdly, in many instances there will be a part beyond the slope where the angle of decline is more gradual until the actual bed of the ocean is reached; this third section is known as the continental rise and may descend to a depth of between 3,500 or 5,500 metres before the actual ocean bed is reached. Geographers then describe all three sections214 as comprising the continental margin. It has been estimated that about onefifth of the seabed comes within the scope of the continental margin.
