Great Barrier Reef

“ After the formation of these flats and islands corals grew upon them. The recent reefs have been elevated at least ten feet, and do not owe their contours to subsidence, yet they form true atolls. The inner channels of the Barrier Reef are maintained free of corals by the great amount of silt held in suspension in the water or deposited to form a blue mud over the bottom. Thus there appears to be nothing in the Great Barrier Reef region to lend support to Darwin's theory of coral reefs. ”

“ A few examples of the material on which the delightful work might be undertaken are given, so that the wealth of one brief strip of beach may be taken as typical of a vast stretch of calm waters within the Great Barrier Reef.
The ridges and furrows of the cyclone season, when the clean sand is covered and stained with weed, dead and living molluscs, coral, leaves carried from the hills by flooded streams, all fermenting in the heat, tell that Christmas is past and March not yet over. Many a year passes without such a storm as compels the groaning ocean to ravage its reefs. ”

“ Following the shoreline of Queensland, at a distance of from ten to one hundred and fifty miles, and stretching for twelve hundred and fifty miles, is the Great Barrier Reef of Australia, one of the wonders of the world. ”

“ The stretch of smooth water that forms a natural harbour for a thousand miles inside the great barrier reef was unimagined. The northern coast land was believed to be uninhabitable by white men; the interior was supposed to be an almost waterless area of intolerable heat, while experts affirmed that if sheep survived at all beneath the tropical suns of Queensland, they would grow hair instead of wool. ”

“ All you've got to do is to steer due west till you sight the Great Barrier Reef which you ought to do to-morrow night; then run the reef down southerly till you come to the first opening--you will find plenty of boat passages--then once you are inside steer west again for Cape Manifold which you'll see thirty or forty miles away. Then follow the coast southerly again till you come to the settlement in Keppel Bay. If you don't like landing there you can go on to Port Curtis--there's a lot o' people there but I don't think they will trouble to ask you many questions. ”

“ With the débris from all these sources the reef is constantly built up until it rises to low-tide level. Higher than this the corals cannot grow, since they are killed by a few hours’ exposure to the air.
Fig. 159. Patch of Growing Corals exposed at an Exceptionally Low Tide, Great Barrier Reef, Australia
When the reef has risen to wave base, the waves abrade it on the windward side and pile to leeward coral blocks torn from their foundation, filling the interstices with finer fragments. ”

“ These islets may coalesce and form a strip of dry land lying some hundred yards or less from the extreme outer edge of the reef, and separated by a wide channel from the mainland. Where the barrier reef is not far from the land there are always gaps in it opposite the mouths of rivers or considerable streams. The outer wall of a barrier reef is steep, and frequently, though not always, descends abruptly into great depths. ”

“ Environment - current issues:
soil erosion from overgrazing, industrial development, urbanization, and poor farming practices; soil salinity rising due to the use of poor quality water; desertification; clearing for agricultural purposes threatens the natural habitat of many unique animal and plant species; the Great Barrier Reef off the northeast coast, the largest coral reef in the world, is threatened by increased shipping and its popularity as a tourist site ”

“ First of all, the north and south central band of Torres Straits, or submarine continuation of the eastern chain, forms the western boundary of the Great Barrier reefs, just as much as does the dry land to the southward. No true independent coral reefs infringe on this band though they come close up to it. There are no wide spread coral reefs round its islets as there are round Darnley and Murray Islands, but only small fringing reefs clinging to the rocks. ”

“ Here, as in Whitsunday Island, the whole of that part of the reef which is visible is converted into land. This is a circumstance of rare occurrence; more usually a snow-white line of great breakers, with here and there an islet crowned by cocoa-nut trees, separates the smooth waters of the lagoon-like channel from the waves of the open sea. The barrier-reefs of Australia and of New Caledonia, owing to their enormous dimensions, have excited much attention: in structure and form they resemble those encircling many of the smaller islands in the Pacific Ocean. ”

“ No theory worthy of notice has been advanced to account for those barrier-reefs, which encircle islands of moderate dimensions. The great reef which fronts the coast of Australia has been supposed, but without any special facts, to rest on the edge of a submarine precipice, extending parallel to the shore. The origin of the third class or of fringing-reefs presents, I believe, scarcely any difficulty, and is simply consequent on the polypifers not growing up from great depths, and their not flourishing close to gently shelving beaches where the water is often turbid. ”

“ As the reef-building corals require food, are preyed upon by other animals, are killed by sediment, cannot adhere to a loose bottom, and may be easily carried down to a depth whence they cannot spring up again, we need feel no surprise at the reefs both of atolls and barriers becoming in parts imperfect. The great barrier of New Caledonia is thus imperfect and broken in many parts; hence, after long subsidence, this great reef would not produce one great atoll 400 miles in length, but a chain or archipelago of atolls, of very nearly the same dimensions with those in the Maldiva archipelago. ”

“ In the Pacific, the lithothamnion ridge always grows along the seaward face of reefs, provided the reef is exposed to the breakers, for the lithothamnion can thrive only in strongly agitated water. This ridge at Maër Island is only about six inches above low tide, for the breakers are not very high, the force of the rollers being partially spent upon the reefs of the Great Barrier six miles to the eastward of the Murray Islands. ”

“ As the smooth water within the shelter of the Great Barrier Reefs affords facilities for steering with great nicety, a steamer, with care, might effect a saving of fuel as well as time by passing through Torres Strait without anchoring. ”

“ The barrier reef—that singular breakwater that makes so much of the circuit of Pacific islands—is carried far to sea at Matautu and Mulinuu; inside of these two horns it runs sharply landward, and between them it is burst or dissolved by the fresh water. The shape of the enclosed anchorage may be compared to a high-shouldered jar or bottle with a funnel mouth. Its sides are almost everywhere of coral; for the reef not only bounds it to seaward and forms the neck and mouth, but skirting about the beach, it forms the bottom also. ”

“ The barrier reef, in fact, constituted a magnificent natural breakwater, upon which the surf eternally broke in a loud, sullen roar of everlasting thunder, while inside it the water was smooth as a mill pond, shoaling very gradually from the reef to the shore of the island, which consisted of a narrow beach of dazzling white sand, bordered by a fringe of thousands of cocoa-nut palms, the long, plume-like branches of which swayed gently in the soft, warm morning breeze. ”

“ Where the channel is narrow, the agency, which on unprotected coasts is most productive of sediment, namely the force of the breakers, is here entirely excluded, and the reef being breached in the front of the main valleys, much of the finer mud from the rivers must be transported into the open sea. As a current is formed by the water thrown over the edge of atoll-formed reefs, which carries sediment with it through the deep-water breaches, the same thing probably takes place in barrier-reefs, and this would greatly aid in preventing the lagoon-channel from being filled up. ”

“ All those colours of shoaling sand and coral beds are only visible when the water is rippled. A few stones, mere specks here and there above the glassy surface alone shew the presence of a reef on which no swell is breaking.
Calm is thus more dangerous to a steamer than storm, for should she approach the reef areas before picking up the beacons and lighthouse that mark the entrances to Port Sudan and Suakin, she runs great risk of striking an invisible reef. Sailing vessels are safe, as whenever they are under way the water is rippled and the reefs easily seen. ”

“ In barrier-reefs it has long been remarked with surprise that the passages through the reef exactly face valleys in the included land, even in cases where the reef is separated from the land by a lagoon-channel so wide and so much deeper than the actual passage itself, that it seems hardly possible that the very small quantity of water or sediment brought down could injure the corals on the reef. ”