56 ('. II. HITCHCOCK — GEOLOGY OF OAHU 



4. Coralline and molluscan limestones commenced to grow as soon as 

 the reef-building animals could migrate hither. Doubtless the work 

 commenced in the first period, and lias continued ever since, coeval with 

 the other phases of growth. If we were to judge of age from the amount 

 of work accomplished we should say the earlier stages of growth cor- 

 responded to the work done elsewhere in the later Tertiary. The slow 

 upbuilding of the volcanic domes and their subsequent erosion required 

 an immensely long period for their accomplishment. The island was 

 also a thousand feet higher than at present, if the Darwinian theory of 

 the origin of coral reefs is true. 



5. Eruption of the amygdaloidal basalt at the Pali. 



6. The chrysolitic basalt formed laccolites at the Pali. Some of the 

 dikes, both in the Kaala and Koolau areas, may have filled fissures at 

 this time. 



7. Eruption of an igneous agglomerate containing pebbles of chryso- 

 lite; may have produced craters in both areas; described typically at 

 the Pali. 



8. Quite widely extended ejection of red ash, clinker, and lava at the 

 Pali, and the formation of Makakilo and Kupuai of the Laeloa craters; 

 some of the Tantalus series of craters. 



9. Ejection of some of the basalts penetrated in sinking artesian wells. 



10. Tuff craters, probably not all active at the same time — the Salt 

 Lake group, Punchbowl, Diamond head, the Koko heads, Kaneohe 

 group, etcetera. The tuffs came up through coral reefs, the land prob- 

 ably being lower than at present ; vegetation as flourishing as at present. 

 Five substages indicated along Oahu Railway and Land Company near 

 Moanalua station. 



11. Decay of the surface of the tuff and, of course, of all the other 

 rocks, so as to produce soils. 



12. Discharge of ashes from Tantalus, Punchbowl, Diamond head, 

 Koko head, and elsewhere, followed by showers of stones. 



13. Numerous eruptions of basalt and formation of most of the Laeloa 

 craters — Knua, Palailai, Kapuai, Kamuki, Mauumae, Rocky hill. 



14. Dikes cutting Punchbowl, Diamond head and coral reef, Kaena 

 point, Kupikipikio, and Koko head. 



15. Time of the accumulation of calcareous talus-breccia with Acha- 

 tinellida) at Diamond head. 



16. Depression. Over the Achatinella beds is a red marine earth 

 abounding in transported coral, shells, fish remains, etcetera, reaching 

 to 40 feet above the sea. At the altitude of 200 feet on the east side of 

 Diamond head, 1 found corals loose on the surface, more readily refer- 

 able to the former presence of the ocean than to their removal from the 



