Pacific Science Volume 19, Number 3, 1965
Permanent URI for this collectionhttps://hdl.handle.net/10125/4106
Pacific Science is a quarterly publication devoted to the biological and physical sciences of the Pacific Region.
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Item type: Item , Magnetic Studies of Rocks and Sediments Obtained by Deep Drilling(University of Hawai'i Press, 1965-07) Belshe, John C.Item type: Item , The Paleomagnetic Significance of Aeromagnetic Surveys of the Hawaiian Islands(University of Hawai'i Press, 1965-07) Malahoff, Alexander; Strange, William E.Aeromagnetic surveys of the Hawaiian Islands have revealed that the primary magnetic anomalies associated with the islands are dipole anomalies caused by the intrusive rocks of the volcanic centers and rift zones. Comparisons of the direction of magnetization indicated by the dipole anomalies with results of laboratory measurements on lavas show that in many cases the lavas possess reverse polarization while the intrusive rocks are normally polarized. These results must be taken into account when interpreting the magnetic field of submerged marine volcanic features such as seamounts and when establishing periods of reversal in the earth's magnetic field.Item type: Item , An Analysis of the Gravity Field Over the Hawaiian Islands in Terms of Crustal Structure(University of Hawai'i Press, 1965-07) Strange, William E.; Woollard, George P.; Rose, John C.Item type: Item , Gravity and Magnetic Fields Over the Proposed Moho Hole Site North of Maui(University of Hawai'i Press, 1965-07) Rose, John C.; Belshe, John C.Item type: Item , Gravity Relations in American Samoa and the Society Islands(University of Hawai'i Press, 1965-07) Machesky, L.F.Item type: Item , Gravity Investigations on the Leeward Islands of the Hawaiian Ridge and Johnston Island(University of Hawai'i Press, 1965-07) Kroenke, Loren W.; Woollard, George P.Item type: Item , A Gravity Survey of the Island of Niihau, Hawaii(University of Hawai'i Press, 1965-07) Krivoy, Harold L.Gravity data collected on Niihau support geologic evidence that the island is an erosional remnant of a dead shield volcano whose center of volcanism was just east of the present Niihau highlands. Bathymetric and gravity evidence offer clues to a genetic link between Niihau and west Kauai; onshore gravity suggests a continuous Bouguer high connecting the two regions. This link would be in accord with ocean-bottom topography, which shows a prominent ridge rising above sea level at Niihau and at Kaula Rock to the west.Item type: Item , A Reconnaissance Gravity Survey of the Island of Kauai, Hawaii(University of Hawai'i Press, 1965-07) Krivoy, Harold L.; Baker, Melville Jr.; Moe, Euguene E.Item type: Item , A Gravity Survey of the Island of Oahu, Hawaii(University of Hawai'i Press, 1965-07) Strange, William E.; Machesky, L.F.; Woollard, George P.Item type: Item , A Gravity Survey of the Island of Kahoolawe, Hawaii(University of Hawai'i Press, 1965-07) Furumoto, Augustine S.Item type: Item , A Preliminary Gravity Survey of the Island of Lanai, Hawaii(University of Hawai'i Press, 1965-07) Krivoy, Harold L.; Lane, Michael P.Item type: Item , A Reconnaissance Gravity Survey of the Island of Molokai, Hawaii(University of Hawai'i Press, 1965-07) Moore, James G.; Krivoy, Harold L.Item type: Item , A Gravity Survey of the Island of Maui, Hawaii(University of Hawai'i Press, 1965-07) Kinoshita, W.T.; Okamura, R.T.Item type: Item , A Gravity Survey of the Island of Hawaii(University of Hawai'i Press, 1965-07) Kinoshita, W.T.Item type: Item , Seismic Reflection Studies of Sediment Thickness Around the Hawaiian Ridge(University of Hawai'i Press, 1965-07) Kroenke, Loren W.Item type: Item , Hawaiian Calderas(University of Hawai'i Press, 1965-07) MacDonald, Gordon A.Hawaiian calderas form by collapse during the last stages of growth of shield volcanoes built by frequent eruptions of tholeiitic basalt. They range from 2-12 miles across, have sunk several thousand feet, and in part have grown piecemeal by coalescence of smaller collapse craters. They may never have formed on some volcanoes, and all are partly or wholly filled by continued eruption. Toward the end of the filling activity slows, and alkalic lavas complete the filling and build a thin cap over the caldera. Gravity studies reveal masses of ultra-dense rocks only 1-2 km below the surface of several of the volcanoes-perhaps olivine-rich cumulates in the feeding pipe of the volcano, or perhaps protrusions of the mantle. The idea that these may have led to formation of the calderas by isostatic sinking of a heavy column culminating in the caldera appears to be negated by the facts that some calderas show no associated gravity high, in some the high is offset to one side of the caldera, and some highs are not associated with any apparent caldera collapse. Caldera formation probably depends on the formation of a magma reservoir within the mass of the shield volcano, with its top within a few kilometers of the summit of the shield. The Glen Coe mechanism of caldera formation seems to be ruled out by the lack of upward displacement of magma around the sinking block. Caldera collapse is probably the result of sinking of a block bounded by inward-dipping conical fractures, permitted by distension of the top of the volcano and removal of support due to drainage of magma into the rift zones, with or without flank eruption. The distension of both the summit region and the rift zones may result from a lateral spreading of the lower part of the ultra-dense core of the volcano.Item type: Item , Seismic Refraction Studies of the Crustal Structure of the Hawaiian Archipelago(University of Hawai'i Press, 1965-07) Furumoto, Augustine S.; Woollard, George P.Item type: Item , The Structure of Koolau Volcano from Seismic Refraction Studies(University of Hawai'i Press, 1965-07) Furumoto, Augustine S.; Thompson, Noel J.; Woollard, George P.Item type: Item , A Seismic Refraction Study of the Koolau Volcanic Plug(University of Hawai'i Press, 1965-07) Adams, William Mansfield; Furumoto, Augustine S.The seismic data from the GASHOUSE line suppOrt the gravity and magnetic data as indicating a plutonic body occurring beneath the center of the Koolau caldera in the vicinity of Kailua, Oahu. This plug has a velo city greater than 7 krn/sec and adjoins material with a velocity of about 4.6 km / sec at the top and to the southeast. The width of the plug is estimated to be about 6 km down to 3-4 km. Reflections from a horizon greater than 3 km deep may indicate an und erlying magma chamber. The top of the plug is about 1600 m deep. Drilling of this plug would have considerable scientific value both geologically and geophysically. An appropriate drilling site would be at the southwest corner of Kaelepulu Pond, which "lies close to the center of the plug as now defined geophysically. Seismic reflection work directly above the dome is also recommended to test the present estimate of the depth based on refraction results .Item type: Item , Ultrasonic Velocities and Related Elastic Properties of Hawaiian Basaltic Rocks(University of Hawai'i Press, 1965-07) Manghnani, Murli H.; Woollard, George P.