HOW ISLANDS ARE BORN

Dominion, Volume 14, Issue 303, 16 September 1921, Page 5

HOW ISLANDS ARE BORN

MOVEMENTS OF THE EARTH'S CRUST. Scroby Sands, off Yarmouth, have ; risen above the sea after lying submerged • for eighty years, says the "Daily Mail.” ■ Their reappearance is probably due to the long drought. In ordinary times the. water from the Rivers Yare and Bure ; keeps the sand from, silting up, but the flow is now not strong enough, to overcome the action of the sea. The appearance of new islands is gon-: erally due to volcanic action or the work 1 of coral insects. But the whole, crust • of the earth is more or lest elastic and subject to changes of level. All the eastern coast of Greenland, from latitude 60deg. to about 70deg. N. '■ has been subsiding for the last four cen-1 turies, so that some of the ancient piles ■ driven into the beach to support the ( boats of the settlers have been gradually. submerged. ’ Again, the island! of Crete has been raised at, its western extremity about 25 feet; so that ancient ports are now high and dry above the sea. While t this action was taking place tho eastern end of the island, sank so much that the ruins of old towns are seen under the water.

The Andaman and Nicobar Islands in' the Bay of Bengal-are the last remnants of a great chain of mountains running south from the Himalayas. But all the' rest up to the Gulf of Martaban weresubmerged many thousand years _ ago, leaving a race of pygmies (the Negrittos) cut off from nil the rest of the world in: their island forests. Our own islands have been subject t<V the same influences within the human 1 period. At one time Great Britain and Ireland, as well as the Orkney and Shetland Islands, were all part of the Continent of Europe. A rise of only 600 . feet would produce this condition again. Before the “continental” period the greater- part of the British Isles north' of the Thames was submerged, and only tho mountains showed above sea-I’vol,' forming an archipelago. These movements of the earth’s crust aro, however, very slow. Probably they did not exceed an average of 2} feet a century. Tho growth of coral islands in tho Pacific Ocean is far more rapid. .In some places they are estimated to havo risen almost eight inches a year, though this is quite exceptional. In regions where volcanic action is more powerful islands appear and disappear very unexpectedly. Some few years ago one appeared off the Arakan coast of Burma. It was at once inspected by' the Marine Survey, and though ib had been scarcely ten days above water, signs of vegetation were already beginning to appear. The seeds mny have been dropped by migrating birds, or perhaps were carried by the wind. Tho life of this baby island was a brief one; for before the report of the Marine Survey was in print it had sunk back into the sea.