NORMAL FAULTING 513 



and the Kipalmhi Gap remained intact. Normal valley erosion could 

 scarcely produce the structural features described. 



Evidence of faulting along the shorelines of Mani has not been ob- 

 served, with the possible exception of the line of cliffs between Kaupo 

 and Kipaluilu, the ends of whicli are hid by younger flows. Similarly, 

 on Lanai and Kahoolawe there is no indication of faulted shorelines. 



On West Maui the lao Valley and on West Oahu the Lualualei basin 

 have both been described as calderas, although satisfactory evidence in 

 support of this view and in opposition to the hypothesis of normal valley 

 erosion has never been presented. 



Molokai is bounded on the north by a fault-line scarp, as was recognized 

 by Lindgren."'^ Two-thirds of the Wailau volcano-^ lias subsided, leaving 

 only a few crags projecting above the water not far from the fault-scarp 

 (plate 31, figure 2). Kalaupapa, north of the fault-line, was formed 

 from three centers of activity along a line perpendicular to the main fault, 



Oahu presents a j)roblem in the Koolaupoko district northeast of Hono- 

 lulu where the pali wall stretches in a curved line from Makapuu Point 

 to Waikane. Branner and others have argued that this pali (cliff) rep- 

 resents a normal erosion feature. The buttressed wall unquestionably 

 shows the effect of erosion and Kaneohe Bay has been somewhat drowned, 

 thus obscuring the drainage systems. 



The wall, 23 miles in length, truncating the heads of the Nuuanu and 

 other valleys extending toward Honolulu (plate 32), appears to the writer 

 to represent a fault-line scarp buttressed by erosion. Such peaks as 

 Olomanu and Manawili would represent crags of the original mountain 

 mass which did not subside. The ridges extending out to Kualoa and 

 Waikane would also represent portions of the original mountain, but the 

 low ridges east of Kaneohe and the rounded hills now cultivated in pine- 

 apples may be eroded cones of 3^ounger age analogous to the ash cones at 

 the head of the pali and the cones below the pali, both in tlie Nuuanu 

 Valley and toward Kaneohe. These cones did not appear until after the 

 major faulting, as is shown by the fact that the ashes from the cone at 

 the top of the pali have covered a portion of the steep pali slope. 



On western Oahu the Lualualei basin and the other broad valleys 

 appear to have been cut by normal erosion before the Koolau volcano 

 attained a sufficient height to rob the Waianae volcano of its rainfall. 

 Drowning to a depth of over 700 feet filled these valleys with gravels and 

 surface wash and obscured their original character. Lava flows in the 

 sides of the Lualaulei basin do not dip away from this basin, but from a 



28 U. S. Geol. Survey, Water Supply Paper 77, 1908. 



29 A name here proposed for the volcano which built east Molokai. 



