The Pacific Ocean has one and three-quarter times the E area of the Atlantic - the next largest division of the hydrosphere - and has more than double its volume of water.
The grander features of the relief of the lithosphere or stony crust of the earth control the distribution of the hydrosphere or collected waters which gather into the hollows, filling them up to a height corresponding to the volume, and thus producing the important practical division of the surface into land and water.
Physical geography naturally falls into three divisions, dealing respectively with the surface of the lithosphere - geomorphology; the hydrosphere - oceanography; and the atmosphere - climatology.
The functions of land forms extend beyond the control of the circulation of the atmosphere, the hydrosphere and the water which is continually being interchanged between them; they are exercised with increased effect in the higher departments of biogeography and anthropogeography.
It merges into physical geography, which takes account of the forms of the lithosphere (geomorphology), and also of the distribution of the hydrosphere and the rearrangements resulting from the workings of solar energy throughout the hydrosphere and atmosphere (oceanography and climatology).
The hydrosphere covers nearly threequarters of the earth's surface as a single and continuous expanse of water surrounding four great insular land-masses known as the continents of the Old World (Europe, Asia, Africa), America, Australia and Antarctica.
Since the Pythagorean school of philosophy upheld the spherical as against the disk-shaped world, some of the ancient geographers, including Eratosthenes and Strabo, looked upon the hydrosphere as forming two belts at right angles to each other, one belt of ocean following the equator, the other surrounding the earth from pole to pole as in the terra quadrifida of Macrobius; while others, including Aristotle and Ptolemy, looked upon the inhabited land, or oikumene, as occupying the greater part of the earth's surface, so that the Indian Ocean was an enclosed sea and India (i.e.
It is convenient to divide the subject-matter of physical geography into the atmosphere, hydrosphere and lithosphere, and in this sense the ocean is less than the hydrosphere in so far as the latter term includes also the water lying on or flowing over the surface of the land.
The hydrosphere is, in fact, continuous, and the land is all in insular masses: the largest is the Old World of Europe, Asia and Africa; the next in size, America; the third, possibly, Antarctica; the fourth, Australia; the fifth, Greenland.