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Geology of Oahu

Charles Henry Hitchcock
Geology of Oahu
Bulletin of the Geological Society of America (1900) 11: 15-57


From the descriptions now presented it is possible to make out the order of the principal events in the geological history of this volcanic island. We are now satisfied with the existence of Tertiary deposits antedating the rise of the earliest basaltic land, but will not consider whether there may have been any rising of the ocean floor in connection with the eruptions. 1. At the base of Kaala [Waianae volcano] igneous eruptions commenced under water to accumulate sheets of basalt until finally the island of Kaala, a smooth dome, rose above the waters, which slowly became covered by vegetation derived from distant regions. 2. This dome became extensively channeled by streams produced as now by the condensation of the moisture brought by the northeast trade winds. Like existing islands under the same conditions, the erosion was greater on the northeastern than southwestern sides. 3. The island of Koolau came up quite near to Kaala in a similar manner, and lava flowed down so as to conceal several hundred feet altitude of the northeast flank of Kaala. Koolau extended out to sea several miles farther to the northeast than at present. 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 has 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 corresponded 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 chrysolite; 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, etc. The tuffs came up through coral reefs, the land probably 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, Kuua, Palailai, Kapuni, 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 Achatinellidae at Diamond head. 16. Depression. Over the Achatinella beds is a red marine earth abounding in transported coral, shells, fish remains, etc, reaching to 40 feet above the sea. At the altitude of 200 feet on the east side of Diamond head, I found corals loose on the surface, more readily referable to the former presence of the ocean than to their removal from the tuff by rain. Professor Lyons writes that he has observed terraces, apparently of marine origin, on the coast side of the Pali 100 feet above tidewater. Brigham and Dutton in their writings agree as to the existence of a depression of the land somewhere about 200 feet at this epoch. Some one asks, Could not the elevation of these organisms have been effected by an earthquake wave? 17. Elevation to the present level. Accumulation of dunes. Notes on the Tertiary geology of Oahu by W. H. Dall 57 Hitchcock rejects an origin by faulting for the Koolau Pali, favoring erosion instead. He also rejects the inference that coral encountered in deep wells was in place and hypothesizes that it drifted downslope. He interprets raised coral sands as having been washed onto land during storms. He cites Brigham's descriptions of the secondary craters [Honolulu Series vents], but adds an observation of coral and lava fragments in the Diamond Head tuff. He describes a dike cutting tuffs and corals on the shore near Diamond Head and reprints (p. 57-60) an article by Dall (1900).

ISSN: 1050-9747
Serial Title: Bulletin of the Geological Society of America
Serial Volume: 11
Title: Geology of Oahu
Pages: 15-57
Published: 1900
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
Accession Number: 1918-017629
Categories: Areal geology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: map
N21°15'00" - N21°43'00", W158°18'00" - W157°39'00"
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data from Bibliography and Index of North American Geology, U. S. Geological Survey, Reston, VA, United States. Reference includes data from U. S. Geological Survey, Hawaiian Volcano Observatory, , United States
Update Code: 1918
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