PUTT WAAWAA.
When one is at the landing of Kawaihae, he may see a curious bill to the south at the base of Hualalai called Puu Waawaa. It is a fluted cone several hundred feet higher than its base which is 3.300 feet above sea level. The name in the Hawaiian lan guage signified fluted. There are numerous ravines radiating from the summit penetrating the slopes for fifty or more feet, all of them apparently formed by the downward flowage of rain water. The material is tuff made of ash or fine gravel contain ing angular fragments—and it has the structure of the ordinary cinder cone, quaquaversal stratification.
This cone is not far removed from the Manna Loa flow of 1859. There is a descent from it to the west of about t,Soo feet to another hill called Puu Anahulu and the slope is bordered on the east by a cliff facing the 1859 flow. This terraced slope has been covered by the lava from both Hualalai and Mauna Loa. Puu Waawaa has also been encircled by lavas from Hualalai which covered up the original floor between the two eminences. The fact of the more ancient age of these cones is very obvious to the observer upon the steamer going north from Kailua. He can see that lava of a darker color has flowed downwards around Pun Waawaa, proving that the fluted cone is older than the basaltic flows. Nor is the fluted character so obvious from the seaward side.
While this cone has arrested attention, Dr. Whitman Cross seems to have been the first scientific man to visit it, and he has published his observations in the Journal of Geology No. 6, Vol. October, 1904, entitled "An occurrence of trachyte on the Island of Hawaii." The terrace bench of Puu Anahulu he represents as made of an agglomerate aggregate of large and small fragments of a felsitic trachyte. The rock here has suf fered decomposition by kaolinization. Both this original and decayed portion "exhibit a rude schistority due to a parallel ar rangement of minute feldspar tablets, like that common in phono lite and some trachyte." The fragments at Puu Waawaa consist of brown pumice, dark aphanitic or black obsidian-like rocks, with some showing a mingling of the latter materials. The dark
aphanitic fragments are not unlike some dense basalts of the island in appearance, yet resemble also the freshest rock from the boulders of Puu Anahulu. "Thin sections of the obsidian show it to be a colorless glass containing streams of feldspar micro lites in some parts and free from them in others. The dull aphanitic streaks and masses are largely crystalline, with more or less of fine magnetic dust and ferritic globulites, and a color less glassy base of variable amount." Chemical analyses of these rocks were made under Dr. Cross' directions by Dr. Hillebrand of the U. S. Geological Survey, and the surmise of their trachytoid character well substantiated. Further notices of the petro graphic character are given in the Appendix.
The finding of lava rich in alkali feldspar, where heretofore only basalt and allied rocks had been noted, is a matter of great importance and Dr. Cross rightly assumes that there may have been quite extensive eruptions of these lavas, and that there is an ancient trachytic island here beneath the basaltic flows from the great volcanoes of Mauna Kea, Mauna Loa, and Hualalai ; and that "if further exposures of the trachytoid rocks are found, it seems to me probable that they will be in the area of the Wai mea plain, which extends practically from Puu Anahulu for twenty miles northeasterly to the north base of Mauna Kea, or in the northern and oldest basaltic section of the island, the Ko hala mountains. The peculiar petrographic character of these rocks therefore substantiates the doctrine heretofore stated, of the greater age of the Kohala group of hills as indicated by the enormous erosion to which they have been subjected.
Mr. R. S. Hosmer informs me that there is an isolated area of dense forest just north of Keokeo in Kona. It should be examined so that it may be determined whether it is underlaid by older rocks or is a spared monument of a once more extensive woodland.