122 ON CORAL REEFS AND ISLANDS. 



But we may derive some additional knowledge respecting this 

 area of subsidence from other facts. 



Hawaiian Range. — We observe that the western islands in 

 the Hawaiian Range, beyond Bird Island, are coral islands, and 

 all indicate some participation in this subsidence. To the east- 

 ward in the range, Kauai and Oahu have only fringing reefs, yet 

 in some places these reefs are half a mile to three-fourths in 

 width. They indicate a long period since they began to grow, 

 which is borne out by the features of Kauai showing a long res- 

 pite from volcanic action. We consequently detect proof of but 

 little subsidence of the islands. Moreover, there are no deep 

 bays : and, besides, Kauai has a gently sloping coast plain of 

 great extent, with a steep shore acclivity of one to three hundred 

 feet, all tending to prove the smallness of the subsidence. We 

 should, therefore, conclude that these islands lie near the limits 

 of the subsiding area, and that the change of level was greatest 

 at the western extremity of the range beyond Kauai. 



Marquesas. — The Marquesas are remarkable for their abrupt 

 shores, often inaccessible cliffs, and deep bays. The absence of 

 gentle slopes along the shores, their angular features, abrupt sound- 

 ings close alongside the islands, and deep indentations, all bear 

 evidence of subsidence to some extent ; for their features are very 

 similar to those which Kauai or Tahiti would present, if buried 

 half its height in the sea, leaving only the sharper ridges and 

 peaks out of water. They are situated but five degrees north of 

 the Paumotus, where eighty islands or more have disappeared, 

 including one at least fifty miles in length. There is suffi- 

 cient evidence that they participated in the subsidence of the 

 latter, but not to the same extent. They are nearly destitute of 

 coral. 



Gamhier or Mangareva Group. — In the Southern limits of 

 the Paumotu Archipelago, where, in accordance with the forego- 

 ing views, the least depression in that region should have taken 

 place, there are actually, as we have stated, two high islands, 

 Pitcairrts and Ganibiefs. There is evidence, however, in the 

 extensive barrier about the Gambier^s (see cut on page 91), that 

 this subsidence, although less than farther north, was by no means 

 of small amount. On page 19, we have estimated it at 1150 feet. 

 These islands, therefore, although towards the limits of the sub- 

 siding area, were still far within it. The valley-bays of the Man- 

 gareva islets are of great depth, and afford additional evidence of 

 the subsidence. 



Tahitian Islands. — The Tahitian Islands, along with Samoa 

 and the Feejees, are near the southern limits of the area pointed 

 out. Twenty-five miles to the north of Tahiti, within sight from 

 its peaks, lies the coral island Tetuaroa, a register of subsidence. 

 Tahiti itself, by its barrier reefs, gives evidence of the same kind 



