LYONS ON LIFE HISTORY OF A VOLCANIC ISLAND. 95 



TIr* isliuul as a luoduct of cniplivc aclivilv is at lasi liiiislit-d. It is a 

 more or less synnnctrical low dome, its slopes extending on the leeward 

 side quite to ilie sea level, on the windward side terminating abruptly 

 in ])r('(ii»iloiis clitTs. I( is already clothed with forest vcjictatiou on 

 the portions receiving- abundant rainfall provided there is oiImm- land n<'ar 

 by whence seeds may be easily brought. It can hardly fail to have 

 some luxuriant ve<;('tation. if only of ferns. Probably only on the lee- 

 ward side will there be lava Hows on which ]ilanr life has not estab- 

 lished itself. There may or may not be a summit crater. It is probable 

 that there will be numerous parasitic cones and there may be also 

 near the sea some tufa cones, but these are minor features, all destined 

 to disajipear without atfectin.i;- the final result of the o]»eration of 

 denndin<i' agencies. 



AN'hat is of much greater consequence is the probability that already 

 the insecurity of the foundation on which the island rests has been 

 manifested in faults that mar th(> symmetry of the mountain, and which 

 may profoundly affect the result of erosive agiMicies by giving 

 unexpected direction to their action. It is this possibility which geol- 

 ogists have hitherto failed to take into account. Some most striking 

 illustrations of such faulting exist in the Hawaiian islands, the signifi- 

 cance of which came to me a few years ago as a most illuminating 

 revelation. 



To me, as to others with whom I had conversed, Waipio valley on the 

 island of Hawaii had been a mystery. A gorge, apparently the work of 

 stream erosion, half a mile wide, with level floor, extends back into 

 the mountain five miles or more, then turns abruptly to the right, 

 pursuing a course parallel with the coast perhaps eight miles, main- 

 taining much of this distance its extraordinary breadth and nearly 

 level floor. On either side the walls rise precipitously 2.000 to 3,000 

 feet, picturesque waterfalls coursing down at intervals from the moun- 

 tain above, but occupying only insignificant gullies. From near the 

 point where the valley heads, there starts a counterpart valley, w^hich 

 follows a course at first jtarallel with the shore line, then abruptly 

 turns seaward, this A'alley also characterized by precipitous sides 

 throughout its course. 



What does it all mean? There can be but one explanation. A section 

 of the mountain, perhaps five miles wide and ten miles long, parallel 

 with the coast has been split away by a fault, dropped down some dis- 

 tance and tilted bodily seaward. To all appearance, another slice ex- 

 ternal to this has slid off and disappeared completely in the deep sea. 

 This has happened in a region of very abundant rain, and stream erosion 

 has played its subordinate part in carving the valley into its present 

 form. No doubt the excessive rain has had something to do also with 

 causing the catastrophe, not as has been supposed by provoking a 

 volcanic explosion, but by solvent action of the water on the constituents 

 of the rock. 



The example does not stand alone. Something very similar must 

 have happened on the island of Molokai, where a somewhat similar 

 valley terminates illogically in a precipice perhaps 400 feet high over 

 which pours the waters of a considerable stream Avhich has not cut 

 for itself a gorge in the cliff. What has taken place you comprehend 



