Emperor Seamounts Research Articles

Instabilities of fluid conduits in a flowing earth -- are plates lubricated by the asthenosphere?

Summary. A laboratory and theoretical study of the stability of conduits of buoyant fluid in a viscous shear flow has been conducted. The object of the study is to explain the formation of discrete islands in island chains such as the Hawaiian Emperor seamount chain, and to investigate a new method by which the variation of shear with depth in the mantle may be determined. The conduits were made by injecting oil into a more viscous oil of greater density. Initially a growing chamber of lower viscosity oil formed near the injector, but when the chamber got sufficiently large it rose as a buoyant spheroid. Behind this trailed a vertical cylindrical conduit through which fluid could continue to rise to the surface as long as the source continued. If the more viscous fluid was sheared laterally the conduit was gradually rotated to a more horizontal position. The diameter of the conduit increased with time due to a decreasing component of gravitational force along the axis of the conduit. When the conduit was tilted to more than 60 with the vertical, it began to go unstable by developing bumps which ultimately initiated a new chamber which rose to a new spot. In addition, if the Reynolds number of the conduit was greater than approximately ten, an axisymmetric wavy instability appeared in the walls of the conduit and the conduit had to be tilted less before a new chamber was initiated. If shear under the Pacific plate has to tilt buoyant mantle plumes to as much as 60 to form the relatively regular island chains associated with hot spots, most of the shear would be found in a zone with a vertical extent of less than 200 km.

Nuclear divisions in pacific pomfret Brama japonica HILGENDORF.

The gonads of the Pacific pomfret pomfret Brama japonica HILGENDOLF collected from the area near the Emperor's Sea Mounts in the North Pacific were used for cytological observations. Mitotic nuclear divisions in spermatogonia showed to have chromosomes of 2n=54. One or two long rod-shaped multivalents frequently appeared at metaphase of meiosis I in spermatocytes.

The Relationships of the Hawaiian Honeycreepers (Drepaninini) as Indicated by DNA-DNA Hybridization

AbstractTwenty-two species of Hawaiian honeycreepers (Fringillidae: Carduelinae: Drepaninini) are known. Their relationships to other groups of passerines were examined by comparing the single-copy DNA sequences of the Apapane (Himatione sanguinea) with those of 5 species of cardueline finches, 1 species of Fringilla, 15 species of New World nine-primaried oscines (Cardinalini, Emberizini, Thraupini, Parulini, Icterini), and members of 6 other families of oscines (Turdidae, Monarchidae, Dicaeidae, Sylviidae, Vireonidae, Corvidae). The DNA-DNA hybridization data support other evidence indicating that the Hawaiian honeycreepers shared a more recent common ancestor with the cardueline finches than with any of the other groups studied and indicate that this divergence occurred in the mid-Miocene, 15-20 million yr ago.The colonization of the Hawaiian Islands by the ancestral species that radiated to produce the Hawaiian honeycreepers could have occurred at any time between 20 and 5 million yr ago. Because the honeycreepers captured so many ecological niches, however, it seems likely that their ancestor was the first passerine to become established in the islands and that it arrived there at the time of, or soon after, its separation from the cardueline lineage. If so, this colonist arrived before the present islands from Hawaii to French Frigate Shoal were formed by the volcanic "hot-spot" now under the island of Hawaii. Therefore, the ancestral drepaninine may have colonized one or more of the older Hawaiian Islands and/or Emperor Seamounts, which also were formed over the "hot-spot" and which reached their present positions as the result of tectonic crustal movement. The cardueline-drepaninine lineage probably diverged from the Fringilla lineage in the late Oligocene, from the New World nine-primaried oscines in the early Oligocene, and from the other oscines in the early Eocene.During this study we also obtained evidence that the vireos (Vireonidae) are not closely related to the New World nine-primaried oscines.

Tertiary Dismemberment of Western North America: ABSTRACT

Before coastal California began moving along the San Andreas fault, strike-slip faults displaced two other large terranes, thereby affecting petroleum maturation and migration. During the early Eocene, the Pacific plate converged against North America, because at that time it moved parallel to the Emperor Seamounts hot-spot trace. Later, when the Pacific plate began to move parallel to the Hawaiian Ridge (43 m.y. ago), the Pacific-Farallon spreading axis was contacting North America at Oregon. Strike-slip faulting, as evidenced by displaced Tertiary paleolatitudes in Alaska, then detached the Wrangellia-Chugach terrane from the Pacific Northwest and began to move it northward. Today, this block, with a pointed leading edge at the Alaska Peninsula, lies between the Aleutia Trench and the Denali fault. Local deformation indicates that during the Pliocene it curved to the west and came to rest along an ancestral Aleutian subduction zone. Magnetic lineations show that in the middle Tertiary another segment of the Pacific-Farallon spreading axis intersected the continent at northern Baja California. A terrane from Vizcaino Bay to the Olympic Peninsula, which included the Sierra Nevada and Klamath Mountains, moved northward along a fault that joined the earlier strike-slip fault near Vancouver Island. This terrane juxtaposed Obispo-block Franciscan rocks from Vizcaino Bay against Salinian-block potassium-rich plutons at the back side of the Sierra Nevada batholith. At the end of the Miocene, the East Pacific rift jumped east and established the present plate b undary, which is detaching continental rocks only from the Gulf of California to Cape Mendocino. End_of_Article - Last_Page 977------------

Marine geology of the Hess Rise: 1. Bathymetry, surface sediment distribution, and environment of deposition

New charts of bathymetry, acoustic character, and sediment distribution describe the Hess Rise, a large oceanic plateau in the central north Pacific. Discrete physiographic provinces on the Hess Rise are the High Plateau, shallower than 3900 m, trending N30°W; the Northeastern Flank, a smooth, gentle slope gradually increasing in depth to the northeast; the Woollard Abyssal Plain, extending farther to the northeast; the Volcanic Province with its high peaks and ridges along the southern margin of the Hess Rise; the Mendocino Fracture Zone to the south, expressed by broad, planar seafloor regions bordered by ridges and scarps; the Western Steps, formed by structural benches on the western side of the Rise; and the Emperor Deep, between the rise and the Emperor Seamounts. Five types of acoustic units have been mapped and interpreted: a transparent layer, predominantly of biosiliceous pelagic clay; a stratified layer, predominantly of nannofossil ooze; a diffuse layer of debris flows that seem to have originated mostly in the Volcanic Province; an opaque horizon commonly formed of volcaniclastic sediments that are usually found on the seafloor of the Mendocino Fracture Zone; and a hyperbolic horizon, indicating outcrops of igneous rock. The pronounced effect of bottom currents on the present‐day environment of deposition in the Hess Rise is evidenced by the presence of the opaque horizon, which is interpreted as an erosion surface, and by current moating, abrupt thinning of surface layers and truncation of subbottom reflectors. The widespread erosion on the seafloor of the Mendocino Fracture Zone is attributed to the flow of Antarctic bottom water.

Early Tertiary rupture of the Pacific plate: 1700 km of dextral offset along the Emperor trough-Line Islands lineament

Between 67 and ∼40 Ma ago a northwest-southeast-trending fracture system over 8000 km long split the Pacific plate and accumulated at least 1700 km of dextral offset between the east and west portions. This system, here named the Emperor fracture zone (EFZ) system, consisted of several segments, one along the present trace of the Emperor trough and another along the Line Islands, joined by short spreading ridges. The EFZ terminated at its northern end against the Kula-Pacific ridge, and at its southern end in a ridge-transform system, called the Emperor spreading system, which extended to the west, north of Australia. The finite angular velocity vector describing the relative motion between the East and West Pacific plates is ∼0.6°/Ma about a pole at 36°N, 70°W. This vector, added to the known Early Tertiary motion of the Pacific plate with respect to the global hotspot reference frame, accounts in large part for the NNW trend of the Emperor seamount chain relative to the WNW Hawaiian trend, without violation of the integrity of the Antarctic plate. The Meiji-Emperor and Emperor-Hawaiian bends date, respectively, the initiation (∼67 Ma ago) and cessation (∼40 Ma ago) of seafloor spreading on the Emperor spreading system. The postulated Early Tertiary relative motion along the EFZ between the East and West Pacific plates explains (1) the present misalignment of the two sets of magnetic bights of the Pacific, (2) the abrupt truncation of eastern Pacific bathymetric lineaments against the Emperor trough and Line Islands, (3) the contrast in paleolatitude between the eastern and western Pacific as indicated by paleomagnetic and sedimentologic studies, and (4) the anomalous gravity signature of the central Hawaiian ridge that indicates that the ridge loaded thin hot lithosphere.

Petrology and K-Ar ages of dredged samples from Laysan Island and Northampton Bank volcanoes, Hawaiian Ridge, and evolution of the Hawaiian-Emperor chain: Summary

The Hawaiian-Emperor volcanic chain is made up of at least 107 indentifiable shield volcanoes (Chase and others, 1970; Bargar and Jackson, 1974; Clague and others, 1980) and is the longest linear island and seamount chain in the Pacific (Fig. 1). Beginning at the active volcanoes Kilauea and Mauna Loa on the island of Hawaii, this chain of volcanoes extends west-northwestward along the Hawaiian Ridge for a distance of 3,500 km, where it turns northward and continues another 2,300 km as the Emperor Seamounts, ending near the intersection of the Aleutian and Kurile Trenches. It is now thought that the Hawaiian-Emperor chain was formed as the Pacific lithospheric plate moved first northward and then northwestward relative to the Hawaiian hot spot, a more or less stable melting anomaly in the asthenosphere, and that the bend in the chain reflects a major change in Pacific plate motion. Several mechanisms have been proposed to explain the Hawaiian (and other) hot spots, including a propagating fracture (Betz and Hess, 1942; Jackson and Wright, 1970); diapiric upwelling along a line of structural weakness (Green, 1971; McDougall, 1971); thermal (Morgan, 1972a, 1972b) or chemical (Anderson, 1975) plumes of gravitationally unstable material rising from the deep mantle; shear melting coupled with thermal feedback (Shaw, 1973) and geographically stabilized by gravitational sinking of refractory residua (Shaw and Jackson, 1973); and extrusion induced by lateral motion along plate boundaries (Handschumacher, 1973). Despite the variety of dynamic models proposed, there has yet to be devised a definitive experiment to test any of them. All these mechanisms are, however, encompassed by the general (or kinematic) hot spot hypothesis, which, when used in the broadest sense, implies neither mechanism nor excess heat.

An assessment of the Th [sbnd]Hf [sbnd]Ta diagram as a discriminant for tectonomagmatic classifications and in the detection of crustal contamination of magmas

The Th Hf Ta diagram, recently proposed [1] as a means of discriminating basalts erupted in various tectonic environments and of detecting crustal contamination in such magmas, is shown to be unsatisfactory for both of its stated purposes. Data are presented for Th, Hf, Ta, Sr and Sr- and Pb-isotopes in basic lavas and a dolerite sill from the ensialic British Tertiary Volcanic Province (BTVP). Taken in conjunction with published results, the isotopic ratios show that some of the BTVP basic magmas are essentially uncontaminated by continental crust, except for the selective introduction of small variable amounts of unradiogenic Pb. Those BTVP magmas which show appreciable isotopic contamination have interacted with either upper or lower crust, or both. Th/(Hf + Ta) is insensitive to contamination with the Th-poor lower crust of cratons but rises during gross contamination with Th-rich upper crust. BTVP basic magmas containing negligible to moderate crustal isotopic components plot in the field of the Th-Hf-Ta diagram occupied by “normal” mid-ocean ridge basalts. Other volcanic provinces of known tectonic setting which plot wholly or partially outside their appropriate fields on the Th Hf Ta diagram are: the Hawaii-Emperor Seamount Chain, the Snake River Plain (Idaho, U.S.A.), the Azores and the Gregory Rift (Kenya).

Tracking a Kuroshio cold ring with a free-drifting surface buoy

A cyclonic ring formed by the Kuroshio Extension southeast of Japan was observed over a 50-day period in 1976 by XBT (expendable bathythermograph), STD (salinity-temperature-depth recorder), and a free-drifting surface buoy. The ring, estimated to be 4 months old, was 240 km in diameter and extended to a depth of at least 3000 m. The satellite-tracked buoy completed 6.5 revolutions around the ring during 37 days as the ring moved 150 m to the north. At the end of this period, the ring coalesced with the kuroshio and the buoy was carried downstream, ultimately drifting 3500 km eastward during the next 7 months. As the buoy passed over the Emperor Seamount chain, it began moving in a series of anticyclonic loops which persisted for nearly one month. An analysis of winds along the buoy trajectory revealed two month-long periods when the buoy velocity was significantly correlated with the wind velocity.

Crust and upper mantle structure along the flank of Kōko Seamount

abstractInversion of an 80-km-long reversed seismic refraction profile near the northwestern flank of Kōko Seamount indicates that the crust adjacent to the southern end of the Emperor Seamount chain is approximately 9-km thick with no dip in the refracting horizons. These data require positive P-velocity gradients in the crust and upper mantle to fit the observed amplitudes.The crustal refractor P velocities and crustal thickness found are in general agreement with those found previously for the Emperor chain and near the Hawaiian Ridge. It is inferred from our data that the tectonic mechanism which created the Emperor and Hawaiian chains was highly localized.

Comments on ‘Lithospheric flexure and uplifted atolls’ by M. McNutt and H. W. Menard

Journal of Geophysical Research: Solid EarthVolume 84, Issue B10 p. 5691-5694 Free Access Comments on ‘Lithospheric flexure and uplifted atolls’ by M. McNutt and H. W. Menard R. D. Jarrard, R. D. JarrardSearch for more papers by this authorD. L. Turner, D. L. TurnerSearch for more papers by this author R. D. Jarrard, R. D. JarrardSearch for more papers by this authorD. L. Turner, D. L. TurnerSearch for more papers by this author First published: 10 September 1979 https://doi.org/10.1029/JB084iB10p05691Citations: 15AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL References Chevalier, J. P., Geomorphology and geology of coral reefs in French Polynesia, Biology and Geology of Coral Reefs, Geology, I O. A. Jones, R. Endean, 113– 141, Academic, New York, 1973. Chubb, L. J., The geology of the Austral or Tubuai Islands, Quat. J. Geol. Soc., 83, 291– 316, 1927. Dalrymple, G. B., R. D. Jarrard, D. A. Clague, K-Ar ages of some volcanic rocks from the Cook and Austral Islands, Geol. Soc. Amer. Bull., 86, 1463– 1467, 1975. Duncan, R. A., I. McDougall, Linear volcanism in French Polynesia, Volcanol. Geothermal Res., 1, 197– 227, 1976. Marshall, P., Geology of Mangaia, Bernice P. Bishop Mus. Bull., 36, 1– 48, 1927. Marshall, P., Geology of Rarotonga and Atiu, Bernice P. Bishop Mus. Bull., 72, 1– 75, 1930. McNutt, M., H. W. Menard, Lithospheric flexure and uplifted atolls, J. Geophys. Res., 83, 1206– 1212, 1978. Summerhayes, C. P., Bathymetry and topographic lineation in the Cook Islands, N. Z. J. Geol. Geophys., 10, 1382– 1399, 1967. Turner, D. L., R. D. Jarrard, K-Ar dating of the Cook-Austral chain: A test of the hot-spot hypothesis, Earth Planet. Sci. Lett., 1979. Vail, P. R., R. M. Mitchum Jr., S. Thompson III, Seismic stratigraphy and global changes of sea level, part 4, Global cycles of relative changes of sea level, Seismic stratigraphy-applications to hydrocarbon exploration, Amer. Ass. Petrol. Geol. Mem., 26, 83– 98, 1977. Watts, A. B., J. R. Cochran, Gravity anomalies and flexure of the lithosphere along the Hawaiian-Emperor seamount chain, Geophys. J. Roy. Astron. Soc., 38, 119– 141, 1974. Wood, B. L., R. F. Hay, Geology of the Cook Islands, N. Z. Geol. Surv. Bull., 82, 103, 1970. Citing Literature Volume84, IssueB1010 September 1979Pages 5691-5694 ReferencesRelatedInformation

Intraplate seismicity on bathymetric features: The 1968 Emperor Trough Earthquake

The April 28, 1968 (mb = 5.5, Ms = 5.2), earthquake in the Emperor Trough, a long linear deep east of the Emperor Seamounts in the North Pacific, is the only recorded seismic event in this region. The focal mechanism, determined using body and surface waves, shows faulting striking along the trough with the east side thrust upward. This mechanism is consistent with bathymetry showing the east flank 500 m higher than the west and suggests that the earthquake represents part of continuing deformation at the trough. This earthquake is one of a large number of intraoceanic plate events that occur on major bathymetric features. The focal mechanisms of earthquakes on such features probably represent the reactivation of already present faults or weak zones. The orientations of intraplate stresses inferred from the focal mechanisms may differ significantly from the true stress directions.

On geoid heights derived from Geos 3 altimeter data along the Hawaiian‐Emperor Seamount Chain

Geoid heights derived from the Geos 3 satellite altimeter show relatively short wavelength (λ 280 km) geoid highs of 5–12 m over the crest of the Hawaiian‐Emperor seamount chain and geoid lows of 1–3 m over flanking regions. These geoid undulations can be generally explained by a simple model in which the load of the seamount chain is supported by a strong, rigid lithospheric plate. The best fitting estimates of the effective elastic thickness of the plate based on data over the Hawaiian Ridge are in the range 25–37.5 km. The elastic thickness cannot be reliably determined from altimeter data over the Emperor Seamounts, although it is probable that it is significantly lower than that obtained for the Hawaiian Ridge. These estimates of the differences in elastic thickness along the seamount chain are in general agreement with previous studies along the chain and provide useful new constraints on the long‐term (>106 years) mechanical properties of the oceanic lithosphere.

The Depth Variability of Meridional Gradients of Temperature, Salinity and Sound Velocity in the Western North Pacific

Abstract In the western North Pacific, meridional gradients of temperature, salinity and sound velocity show considerable variation with depth. Gradients of frontal intensity (more than three times the rms value) occur in the upper 600 m of the ocean. Fronts in the surface layer are spaced at irregular intervals. Many deep fronts have no surface manifestation and are spaced at intervals between 300 and 600 km. A spectral analysis of the meridional gradients as functions of depth and longitude was carried out for the wavenumber range between 0 and 13.4 cycles per 1000 km (c.p. 1000 km). The shape of the power density spectra strongly depends on depth. In the upper 150 m the shape is irregular. Between 300 and 600 m, the spectra show a well-defined peak between 1.5 and 3.3 c.p. 1000 km and a sharp decrease in power beyond 10 c.p. 1000 km. While the shape of the power density spectra shows little variation with longitude, there is a substantial decrease in the total power when crossing the Emperor seamount c...

A New Fusitriton from the Emperor Seamounts in the North Pacific

A New Fusitriton from the Emperor Seamounts in the North Pacific

An analysis of isostasy in the world's oceans 1. Hawaiian‐Emperor Seamount Chain

Cross‐spectral techniques have been used to analyze the relationship between gravity and bathymetry on 14 profiles of the Hawaiian‐Emperor seamount chain. The resulting filter or transfer function has been used to evaluate the state of isostasy along the chain. The transfer function can be best explained by a simple model in which the oceanic lithosphere is treated as a thin elastic plate overlying a weak fluid. The best‐fitting estimate of the elastic thickness of the plate is in the range 20–30 km. Analysis of individual profiles shows significant differences in the elastic thickness along the seamount chain. Relatively low estimates of the elastic thickness were obtained for the Emperor Seamounts north of 40°N, and relatively high estimates for the Emperor Seamounts south of 40°N and the Hawaiian Ridge. These differences cannot be explained by a simple model in which there is a viscous reaction to the seamount loads through time. The best explanation is a simple model in which the elastic thickness depends on age and hence temperature gradient of the lithosphere. The low values can be explained if the Emperor Seamounts north of 40°N loaded a relatively young hot plate, and the high values can be explained if the Emperor Seamounts south of 40°N and the Hawaiian Ridge loaded a relatively old cold plate. These estimates of the elastic thickness along with determinations from other loads on the Pacific lithosphere suggest that the elastic thickness corresponds closely to the 450 ± 150°C isotherm, based on simple cooling models. Thus the large deformations and associated flexural stresses (>1 kbar) at seamount loads do not appear to change appreciably through time. This conclusion is in agreement with subsidence data along the seamount chain and with some gravity observations in the continents.

Absolute motion of an individual plate estimated from its ridge and trench boundaries

A method is presented for estimating the absolute motion of an individual plate using only the locations of trenches or ridges along the boundary of the plate. The change in trend of the Hawaiian–Emperor seamount chain is shown to be consistent with a chasuring the early Cainozoic in absolute plate motion produced by a change in the location of ridges and trenches along the boundary of the Pacific plate.

Paleomagnetism of Suiko Seamount, Emperor Seamount Chain

Using data from a topographic and magnetic survey, the magnetization vector of Suiko seamount near the middle of the Emperor seamount chain (44.5°N, 170°E) was calculated. An inclination of −31° ± 9° and a declination of 213° ± 9° was found, although the goodness ratio is poor (R = 1.1). The paleolatitude thus found (17° ± 5°) is significantly different from its present latitude, supporting the theory that the Emperor‐Hawaii chain has been formed by the Hawaiian hot spot. Magnetization of the seamount is reversed, agreeing with the recent DSDP results.

The magnetic properties of some DSDP basalts from the North Pacific and inferences for Pacific plate tectonics

One hundred seven basalt samples from seven DSDP sites in the North Pacific studied for magnetic properties were found to have a mean magnetization of 0.005 emu/cm3, a mean susceptibility of 0.001, and a mean Koenigsberger ratio of 10. The mean remanence coercivity as measured by the mean demagnetizing field is 90 Oe. The titanomagnetite in most of these old (13–115 m.y.) and highly fractured basalts has been largely oxidized to titanomaghemite during sea floor weathering. The titanomaghemitization is manifest in an increase in Curie temperature from about 160°C to 300°–350°C and a threefold to fourfold decrease in the saturation magnetization. Although a 50% decrease in remanence intensity and susceptibility can be attributed to oxidation at one site, the relation between degree of oxidation and these two properties is obscured at most sites by magnetic grain size differences. A decrease in remanence intensity no doubt occurs but was not observed because the most highly oxidized basalt, that in thin flows and in the margins of thicker flows, is also the finest grained and therefore had a higher initial remanence intensity. Remanence coercivity, while mainly dependent on magnetic grain size, increases about 50% with oxidation. The remanence direction does not appear to be affected by oxidation. Although the remanance inclinations differ considerably from the present geomagnetic field inclination at most sites, the expected range of secular variation is such that the remanence, with the exception ofthat in Meiji Seamount, could have been acquired by the basalts at the present site latitudes. But the site paleolatitudes calculated from the remanence inclinations correspond more closely to the paleolatitudes predicted by assuming that the Pacific plate has moved northward with the motions deduced by Morgan and others from linear volcanic chains. In particular, the coincidence of the magnetic paleolatitude, 19°, measured in Meiji Seamount at the northern end of the Emperor Seamount chain, with the latitude of the island of Hawaii, supports the fundamental assumption of the Morgan model of Pacific plate motion, wherein the volcanic locus or ‘hot spot’ forming the Emperor‐Hawaiian chain has remained essentially stationary with respect to the earth's axis.

Evidence for northward movement: of the Emperor Seamounts

Seismic reflection profiles show that the principal guyots in the Emperor Seamounts as far north as lat 45° 30′ are capped by ancient coral reefs. Ocean temperatures during the Cenozoic were probably not warm enough to permit reef growth at the present latitudes of even the southernmost of the Emperor volcanoes investigated. The results of our study indicate northward movement of the Emperor Seamounts as predicted by the hot-spot hypothesis.