The royal natural history . DIAGRAM EXPLAINING THEORY OF SUBSIDENCE. mountain-peaks which have disappeared below the surface. The coral-rock hasgreatly increased in thickness, and almost entirely covers the former island. Such an ideal section corresponds exactly with the reality. In the followingillustration the outline of the island of Aiva, one of the Fiji group, is given. Inthe lagoon there are two islands resembling the summits of mountains, just as inthe diagram. The exact altitudes and depths are unfortunately not known, but itwill be seen how well the theory of subsidence appears to ex
The royal natural history . DIAGRAM EXPLAINING THEORY OF SUBSIDENCE. mountain-peaks which have disappeared below the surface. The coral-rock hasgreatly increased in thickness, and almost entirely covers the former island. Such an ideal section corresponds exactly with the reality. In the followingillustration the outline of the island of Aiva, one of the Fiji group, is given. Inthe lagoon there are two islands resembling the summits of mountains, just as inthe diagram. The exact altitudes and depths are unfortunately not known, but itwill be seen how well the theory of subsidence appears to explain the conditions. The chief objections which have been made to this theory of subsidence are. OUTLINE OF THE ISLAND OF AIVA. WITH PROJECTED SECTION. the following. The simultaneous occurrence of atolls, barrier-reefs, and fringing- reefs in neighbouring regions does not coincide with the theory, nor does the appearance of atolls and barrier-reefs in regions in which recent elevation of the laud has been proved. The discovery of extensive submarine banks of sediment formed of the calcareous portions of foraminifera, deep-sea corals, molluscs, etc., lakes it possible to explain the formation of atolls and barrier-reefs without the of subsidence, this explanation being more probable than that involving the :ing of extensive areas of land. The formation of atolls can be explained by CORALS. 525 the better growth of the corals on the outer edges of the reef which are mostexposed to the action of the surf, and the sweeping of the coral material out of thelagoon through the agency of oceanic currents, and the dissolving action of thecarbonic acid contained in the sea, water. The deep
Size: 1874px × 1333px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, booksubjectnaturalhistory, booksubjectzoology
