40 C. H. HITCHCOCK — GEOLOGY OF OAHU 



winds and storms from their source, filling the valley, and were deposited 

 lower down. These leaf beds are elevated about 20 feet above tidewater. 



SECTION NEAR MO ANAL LA 



A more detailed study of the relations of several deposits is possible 

 in the bluffs less than half a mile west from Moanalua station along 

 the railroad. The first exposure is of a raised limestone, containing 

 marine shells and broken corals, apparently declining beneath earthy 

 tufTaceous beds in a westerly direction. Following the blur!', after a gap 

 in the continuity, there is an excellent exposure for many rods where 

 fresh excavations have been made for the railroad. It shows even better 

 now than when photographed (plate 6, figure 2). The bluff is estimated 

 to be 40 feet high. The lower portion is an earth or soil existing before 

 the eruption from Aliipakai, for trees grew on it and were not consumed 

 at the time of the eruption. Their stems stand upright in the tuff, as 

 ma}' be seen by a scrutiny of the figure. This upper layer ma}' be 10 

 or 12 feet thick and the stems can be seen along the whole length of the 

 bluff, some of the holes being a foot in diameter. It is easy enough to 

 imagine the scene. There was a forest growth on the soil of the lower 

 part of the section. Showers of sand and stones covered the forest 10 

 feet deep, occupying the spaces between the stumps, and in the course 

 of years a new soil accumulated and vegetation assumed its sway on the 

 surface of the tufa, and the impressions made by the stubs remain, either 

 hollow or filled by miscellaneous mud. They are like the upright tree- 

 casts found in the cliffs of the Joggins, Nova Scotia. 



Following this bluff to the west, one notices that the tufa sinks down 

 in small waves, due to the giving way of masses of the loose soil beneath. 

 Near the west end of the bluff both the tuff and soil appear, and the 

 latter is underlaid by a coral reef 8 or 10 feet thick. This is underlaid 

 again by tuff, as seen under the iron rails, and toward the sea there is 

 coral again. Hence the succession, as indicated here, is : 



1. The main coral reef. 



2. Thin layer of tuff. 



3. Coral reef or limestone. 



4. Decomposed rock sustaining a soil covered by forest. 



5. Eruption of tuff from Aliapakai covering the country from the promontory 

 east of Moanalua to Puuloa and heyond. 



6. There may be added a long interval of time during which the gorge in the 

 upper Moanalua stream has been excavated. 



As one follows the railroad beyond the bluff he can see the long 

 gradual slope from Aliapakai extending indefinitely toward Pearl river. 

 The rocks come to the surface everywhere. Beyond Puuloa station 



