Wide areas, giving rise to oceanic depressions and leaving the continents protuberant; the other, folding along comparatively narrow belts, giving rise to mountain ranges.
The Trachylinae, on the other hand, are above all oceanic forms, and have no polyp-stage, and hence there is typically no alternation in their life-cycle.
The general scheme of oceanic circulation was made out prior to 1910.
The continental area is on one side of the sphere and the oceanic on the other.
The flora falls naturally into three great divisions: that of the Amazon basin where exceptional conditions of heat and moisture prevail; that of the coast where heat, varying rainfall, oceanic influences and changing seasons have greatly modified the general character of the vegetation; and that of the elevated interior, or sertao, where dryer conditions, rocky surfaces, higher sun temperatures and large open spaces produce a vegetation widely different from those of the other two regions.
The movement of emigration may be divided into two currents, temporary and permanentthe former going chiefly towards neighboring European countries and to North Africa, and consisting of manual laborers, the latter towards trans-oceanic countries, principally Brazil, Argentina and the United States.
Where the central oceanic buckle attains the water-line we have our oceanic islands, seen in our type ocean, as St Helena and the Azores.
Oceanic islands are divided according to their geological character into volcanic islands and those of organic origin, including coral islands.
Now it is probable that the main cause of oceanic circulation is the driving force of the winds upon the superficial layers of water.
Upon the denuded edges of the Scotland beds lies the Oceanic series.
The Oceanic series is generally overlaid directly, and unconformably, by coral limestones; but at Bissex Hill, at the base of the coral limestones, and resting unconformably upon the Oceanic series, there is a Globigerina marl.
The honour of first sounding really oceanic depths belongs to " Egeria," " Waterwitch," " Dart," " Penguin," " Stork," Sir James Clark Ross, who made some excellent measurements and " Investigator."
Large angles of slope may, however, occur on the flanks of oceanic islands and the continental borders.
A definite terminology for the larger forms of sub-oceanic relief was put forward by the International Geographical Congress at Berlin in 1899 and adopted by that at Washington in 1004.
The continental shelves include not only the oceanic border of the continents but also great areas of the enclosed seas and particularly of the fringing seas, the origin of which through secular subsidence is often very clearly apparent, as for instance in the North Sea and the tract lying off the mouth of the English Channel.
The greatest of the intercontinental seas, the Arctic, comes nearest to oceanic conditions in the extent and depth of its depressions.
The nature of the change of temperature with depth below 2500 fathoms is entirely dependent on the position of the sub-oceanic elevations, for the rises and ridges act as true submarine watersheds.
Buchan, " Specific Gravities and Oceanic Circulation," Trans.
Richard, L'Oceanographie (Paris, 1907); List of Oceanic Depths and Serial Temperature Observations, received at the Admiralty in the year 1888 (et seq.) from H.M.
Many of the oceanic islets are composed of coral limestone, which in this way becomes phosphatized; others are igneous, consisting of trachyte or basalt, and these rocks are also phosphatized on their surfaces but are not so valuable, inasmuch as the presence of iron or alumina in any quantity renders them unsuited for the preppration of artificial manures.
Hence the proportion of purely oceanic area to the total area is greater in the Pacific than in the Atlantic, the supply of detritus being smaller, and terrigenous deposits are not borne so far from land.
The Pacific has few islands; the oceanic islands are volcanic, and coral formations are of course scanty.
Next, dependent on the inclination of the earths axis, is the division of the planetary year into the terrestrial seasons, with winter and summer changes of temperature, wind-strength and precipitation: these seasonal changes are not of the restrained measure that is characteristic of the oceanic southern temperate zone, but of the exaggerated measure appropriate to the continental interruptions of ~the northern land-and-water zone, to which the term temperate is so generally inapplicable.
The "Mediterranean region," as a geographical unit, includes all this area; the Black Sea and the Sea of Marmora are within its submerged portion, and the climate of the whole is controlled by the oceanic influences of the Mediterranean Sea.
The origin and development of these conditions, in islands so distinctly oceanic as the Galapagos, have given its chief importance to this archipelago since it was visited by Darwin in the "Beagle."
The terrace closest to the land, known as the continental shelf, has an average depth of 600 ft., and connects Australia, New Guinea, and Tasmania in one unbroken sweep. Compared with other continents, the Australian continental shelf is extremely narrow, and there are points on the eastern coast where the land plunges down to oceanic depths with an abruptness rarely paralleled.
Newfoundland, the West Indies, and the Falklands, and the chief oceanic islands are the Azores, Madeira, the Canaries, the Cape Verde Islands, Ascension, St Helena, Tristan da Cunha and Bouvet Island.
This order, containing the typical oceanic medusae, is divided into two sub-orders.
Thus the best approximation to the average depth of the ocean is little more than an expert guess; yet a fair approximation is probable for the features of sub-oceanic relief are so much more uniform than those of the land that a smaller number of fixed points is required to determine them.
The latter rise abruptly from the oceanic abysses.
The direct geographical elements are the arrangement of land and sea (continents and islands standing in sharp contrast) and the vertical relief of the globe, which interposes barriers of a less absolute kind between portions of the same land area or oceanic depression.
The proportion of salt in the water of the Caspian, though varying in different parts and at different seasons, is generally much less than the proportion in oceanic water, and even less than the proportion in the water of the Black Sea.
Those of the highest zone are remarkable for the great predominance of predaceous species and of wingless forms. In this last respect they present a striking analogy with the endemic coleopterous fauna of oceanic islands.
Each of the larger islands has one or more ports which a local steamboat serves regularly, and Honolulu has the regular service of seven trans-Pacific lines (the American-Hawaiian Steamship Co., the Canadian-Australian Steamship Co., the Matson Navigation Co., the Oceanic Steamship Co., the Pacific Mail Steamship Co., the Mexican Oriental and the Toyo Kisen Kaisha); it is a midway station for vessels between the United States (mainland) and Australia and Southern Asia.
There are trans-oceanic lines to Japan and China, to the Philippines and Hawaii, and to London, Liverpool and Glasgow, by way of the Suez Canal.
The following islands may be classified as oceanic, but not with any of the three main divisions: the Bonin Islands, north of the Marianas, belonging to Japan; Lord Howe and Norfolk Islands (to New South Wales); Easter Island (to Chile); the Galapagos Islands (to Ecuador).
The following paragraphs review the oceanic islands generally, and are therefore concerned almost entirely with the central and mid-western parts of the ocean.
In1525-1527Garcia Jofre de Loyasa sailed to the Moluccas, but, like Magellan, missed the bulk of the oceanic islands.
In the oceanic islands of the Pacific three different peoples occur, who have been called Melanesians, Polynesians and Micronesians.'
That the oceanic blacks form one family there can be no doubt, and it is evidence of the immensely remote date at which their dispersion began that they have a multitude of languages often unintelligible except locally, and an extraordinary variety of insular customs: differentiations which must have needed centuries to be effected.
Codrington (Melanesian Languages) has adduced evidence to prove that Melanesia is the most primitive form of the oceanic stock-language, and that both Malays and Polynesians speak later dialects of this archaic form of speech.
One of the most obscure questions with which the ethnologist has to deal is that of the prehistoric remains which occur in different and widely separated parts of the oceanic region.