Showing papers by "University of Rhode Island published in 1978"
1,142 citations
TL;DR: In the early Pliocene, a sinistral-to-dextral change in the coiling-direction preference in Pulleniatina 3.5 m.y.
Abstract: Pliocene and Pleistocene planktonic foraminiferal biogeography and paleoceanography have been examined in Deep Sea Drilling Project (DSDP) sites of the Panama Basin (Pacific Ocean) and Colombian and Venezuelan Basins (Atlantic Ocean) to determine the timing of the isolation of Atlantic and Pacific tropical planktonic faunas resulting from the development of the Central American isthmus. Previous studies have suggested a late Miocene to middle Pliocene occurrence of this event. The Panama Basin (DSDP site 157) and the Colombian Basin (DSDP site 154A) share two early Pliocene biogeographic events: (1) great abundance of sinistral coiling Neogloboquadrina pachyderma at 4.3 m.y. ago at site 157 and 0.7 m.y. later at site 154A, and (2) a sinistral-to-dextral change in the coiling-direction preference in Pulleniatina 3.5 m.y. ago at both locations. Identification of these events farther to the east in the Venezuelan Basin (DSDP site 148) is complicated by insufficient lower Pliocene core recovery, but abundant sinistral N. pachydcrma appear to have extended far to the east in the Caribbean 3.6 m.y. ago; perhaps the early Pliocene abundance of this form is not indicative of cool water. The coiling-direction history and stratigraphic ranges of Pulleniatina became different in the Atlantic and Pacific Oceans during the early Pliocene; this is inferred to result from geographic isolation of the assemblages. Saito (1976) used the temporary disappearance of this genus from Atlantic waters at 3.5 m.y. ago to mark the closure of the Isthmus of Panama, but I show that in the Colombian Basin (site 154A) its disappearance was closer to 3.1 m.y. ago. This suggests the possibility of surface-water communication between the Atlantic and Pacific until that time.
307 citations
TL;DR: In this article, the rates of release of dissolved water from the particles in a pyroclastic flow by diffusion are estimated for flows of thickness 1 to 20 m, which experimental studies demonstrate are the velocities required to fluidise fine to medium ash.
Abstract: Estimates are presented for the rates of release of dissolved water from the particles in a pyroclastic flow by diffusion. Velocities of gas escaping from pyroclastic flows of different thicknesses are calculated. For quite small residual gas contents (0.2 to 0.8% H2O), gas velocities of 10 to over 100 cm/sec during the first 103 sec of release are estimated for flows of thickness 1 to 20 m, which experimental studies demonstrate are the velocities required to fluidise fine to medium ash. Flows with high residual gas contents or large volume (thick flows) are likely to be substantially fluidised by exsolving gas. 30% to over 60% of the particles in such flows are predicted to be fluidised. Fluidisation is thus believed to be an important mechanism in the flow and in determining the mobility of the large magnitude, prehistoric pyroclastic flows which formed extensive ignimbrite sheets. Small pyroclastic flows, however, of the magnitude observed in several historic eruptions are not believed to be fluidised, because of their low residual gas contents, small volume, and the substantial amount of cooling that occurs during their emplacement.
305 citations
TL;DR: In this article, the Raman spectra of FeO, Fe3O4, α-Fe2O3, α -FeOOH, and γ-FeOH, the common products of iron oxidation have been measured.
Abstract: Raman spectra of FeO, Fe3O4, α-Fe2O3, α-FeOOH, and γ-FeOOH, the common products of iron oxidation, have been measured. The spectra of FeO and Fe3O4 appear to be identical. Armco iron oxidized in air at 250°C was examined by Raman spectroscopy after varying periods of exposure and the surface film was found to contain Fe3O4 and α-Fe2O3.
286 citations
TL;DR: In this article, the problem of performing target motion analysis using noisy bearing measurements derived from multiple observation platforms or from a single moving observer is addressed, and the properties of an estimator based on a Cartesian model of the process are detailed.
Abstract: The problem of performing target motion analysis using noisy bearing measurements derived from multiple observation platforms or from a single moving observer is addressed. For the latter case, the properties of an estimator based on a Cartesian model of the process are detailed. Methods of providing estimates both before an observer maneuver, when the process is unobservable, and following an observer maneuver are developed. The results of an experimental study are presented.
278 citations
TL;DR: The phreatomagmatic analogue of plinian tephra is the phreatoplinian pyroclastic deposits as mentioned in this paper, formed by the interaction of water and silicic magma during explosive eruptions.
Abstract: We have recognized a type of pyroclastic deposit formed by the interaction of water and silicic magma during explosive eruptions. These deposits have a widespread dispersal, similar to plinian tephra, but the overall grain size is much tiner. Several deposits studied can be associated with caldera lakes or sea water and water/magma interaction is proposed to account for the fine grain size. Several examples have been studied, including the Oruanui Formation, N.Z., and the Askja 1875 deposit. Both show little downwind decrease in median diameter, a downwind decrease in sorting (σφ) (more evident in the Askja deposit) and coarse tail grading. The Askja example has base surge deposits near source and some Oruanui members show multiple thin beds near source; both are common features of phreatomagmatic deposits. Isopachs of the Askja deposit indicate a source under Lake Oskjuvatn in Askja Caldera and those of the Oruanui indicate a source under the NW part of Lake Taupo. In terms of dispersal area, volume and calculated eruption column heights, these deposits are similar to plinian. However, their extreme fragmentation due to magma/water interaction, superimposed on fragmentation imparted by carlier vesiculation, gives a much finer and more complex grain size distribution than plinian counterparts. The field of phreatomagmatic equivalents to plinian pumice deposits was unoccupied onWalker’s (1973) classification of explosive volcanic eruptions. Such deposits are the phreatomagmatic analogue of plinian deposits and the name « phreatoplinian » is proposed.
261 citations
TL;DR: In this article, the authors show that the Azores mantle plume is 10 to 30 times enriched in LIL elements with very small (⪢ 0.1 < D < 1) bulk crystal/melt partition coefficients (Rb, Cs, Ba, La).
241 citations
TL;DR: Songs of the humpback whale Megaptera novaeangliae were recorded and analyzed from Grand Turks in the Bahamas to Venezuela and it is suggested that songs from other populations are quite different.
Abstract: Songs of the humpback whale Megaptera novaeangliae were recorded and analyzed from Grand Turks in the Bahamas to Venezuela. The design features of the song are as follows. The basic song evolves through a series of different sounds in a fixed order. The song is produced only in the winter tropical calving grounds, just before the whales arrive on the banks. Redundancy is high in that syllables, motifs, phrases and the entire song are repeated. Low, intermediate, and high-frequency sounds are scattered throughout the song. One sound is associated with blowing. The song appears to be partially different each year and there are some differences within a year between banks which may indicate that dialects are present. It is suggested that songs from other populations are quite different. The apparent yearly changes do not occur at one point in time. Only single individuals produce the song and they are hypothesized to be young, sexually mature males. The implications of these various design features are discussed.
220 citations
TL;DR: In this paper, the authors present data on the rheological properties of small lava flows which were erupted on Mount Etna in 1975, using field measurements using a new field viscometer, a shear vane attached to a torque wrench, a conventional penetrometer and various field techniques for estimating rheology properties from the dimensions of lava flows.
Abstract: KNOWLEDGE of magma rheology is required to understand many igneous and volcanic processes. Viscosities of silicate melts can be estimated from their chemical composition and temperature using empirical methods1–3. However, the validity of these estimates has been established only at supraliquidus temperatures where common igneous melts behave as newtonian fluids. Recent experimental evidence from field and laboratory studies4–7, has demonstrated that, at subliquidus temperatures, some magmas behave as non-newtonian fluids due to the presence of dispersed crystals and gas bubbles and possibly as a consequence of structuring in the silicate melt. We present data here on the rheological properties of small lava flows which were erupted on Mount Etna in 1975. These data were obtained by field measurements using a new field viscometer8, a shear vane attached to a torque wrench, a conventional penetrometer and various field techniques for estimating rheological properties from the dimensions of lava flows.
198 citations
TL;DR: An anticyclonic lens of water in the permanent thermocline off the Bahamas has water mass characteristics representing Mediterranean and eastern Atlantic central waters that point to baroclinic eddies as a specific mechanism for large-scale mixing.
Abstract: An anticyclonic lens of water in the permanent thermocline off the Bahamas has water mass characteristics representing Mediterranean and eastern Atlantic central waters. This eddy's ability to translate across the Atlantic without losing its identity points to baroclinic eddies as a specific mechanism for large-scale mixing.
183 citations
TL;DR: The boatwhistle, the mating call of the oyster toadfish Opsanus tau L, undergoes a pronounced seasonal cycle where the fundamental frequency increases to a peak early in the summer and then decreases markedly in the middle of July.
Abstract: The boatwhistle, the mating call of the oyster toadfish Opsanus tau L. undergoes a pronounced seasonal cycle. The fundamental frequency increases to a peak early in the summer and then decreases markedly in the middle of July. The call duration decreases coincident with the fundamental frequency. It is hypothesized that these fluctuations are controlled by hormonal factors although temperature exerts a direct effect on the fundamental frequency. The fundamental frequency of the boatwhistle in early season is higher in southern populations than in northern ones. Part of this increase is attributed to increased temperature of southern waters. Call duration, which is independent of temperature, varies irregularly up and down the coast.
TL;DR: Draining of high-level magma reservoirs of central volcanoes during rifting episodes can result in up to 70 km lateral magma flow within the crust and caldera collapse as discussed by the authors.
Abstract: Draining of high-level magma reservoirs of central volcanoes during rifting episodes can result in up to 70 km lateral magma flow within the crust and caldera collapse.
TL;DR: Turekian et al. as mentioned in this paper used radiolaria found in recent surface sediment samples from the eastern North Pacific to identify four assemblages which can be related to the physical oceanography of the California Current.
TL;DR: In this article, changes in the cephalothorax length and dry weight of Formalin-preserved copcpodite and adult Acartia clausi were followed from 12 March-l June 1976 and naupliar weights and lengths determined for one sample.
Abstract: Changes in the cephalothorax length and dry weight of Formalin-preserved copcpodite and adult Acartia clausi were followed from 12 March-l June 1976 and naupliar weights and lengths determined for one sample. Preservation in Formalin caused a significant loss of dry weight, carbon, and nitrogen in adult females, mostly during the first 24 h, but did not significantly affect the C:N ratio or the cephalothorax length of the animals. Length and weight were inversely related to seawater temperature at the time of sampling. As the animals became older this relationship was increasingly affected by their past temperature history. Separate linear relationships between log length and log weight were observed for the nauplii, the CIs, the CII-CVs, and the adults, making it possible to estimate the weight of individual stages from measurcmcnts of length. Animals collected on the same day frorn different stations sometimes showed significant differences in weight for a given length. Such differences could be more clearly expressed by calculation of a condition factor relating weight to the cube of cephalothorax length. The differences in the condition factor appeared to be related to food availability and such differences may be even more apparent when weights of live animals are examined.
TL;DR: In this article, the development of Cenozoic planktonic biogeography of the Southern Ocean is intimately linked with the evolution of the southern Ocean water masses themselves, including the formation of the Circum-Antarctic Current system as obstructing land masses moved apart.
01 Jan 1978
TL;DR: The Narragansett Bay model is designed to represent the current understanding of the bay in its present state as described in Chapter 1, but cannot change to different system states that may result from large increases in organic inputs, drastic changes in salinity, anoxic bottom waters, etc.
Abstract: It has frequently been suggested that numerical ecosystem models should be applied directly to problems of environmental management as a tool for predicting the response of natural systems to perturbations and modifications of various kinds. Our feeling is that while such applications may be instructive, the results must be interpreted with caution and a healthy skepticism. There are, after all, many differences between model systems and real ecosystems. At best, the Narragansett Bay model is designed to represent our current understanding of the bay in its present state as described in Chapter 1. If the natural system is changed in some fundamental way, the conceptual model that lies behind all of the equations and computer programming may no longer apply. As it is presently designed, for example, the model cannot change to different system states that may result from large increases in organic inputs, drastic changes in salinity, anoxic bottom waters, etc. This is not to say that such restructuring cannot be modeled, perhaps even by modifications of the original program. But no model can reasonably be expected to deal with all possibilities, and thus may fall far short of representing or anticipating an event in the natural system.
TL;DR: The authors proposed a model to explain the variations in the surface morphology of many basaltic lava flows before and after an eruption, which may explain the observed non-newtonian characteristics of many lava flows.
Abstract: BEFORE eruption, most basaltic lava flows lose volatiles, either by Hawaiian—or Strombolian-type fire-fountaining. This gas loss may be of fundamental importance in explaining the observed non-newtonian characteristics of many lava flows. The model proposed here also helps to explain the variations in the surface morphology of many basaltic lava flows.
TL;DR: In this paper, the authors investigated the thickness, grain size and texture of the Toba deep-sea tephra layer in order to demonstrate the use of deep sea tectra layers as a volcanological tool.
Abstract: The eruption of Toba (75,000 years BP), Sumatra, is the largest magnitude eruption documented from the Quaternary. The eruption produced the largest-known caldera the dimensions of which are 100 × 30 km and which is surrounded by rhyolitic ignimbrite covering an area of over 20,000 km2. The associated deep-sea tephra layer is found in piston cores in the north-eastern Indian Ocean covering a minimum area of 5 × 106 km2. We have investigated the thickness, grain size and texture of the Toba deep-sea tephra layer in order to demonstrate the use of deep-sea tephra layers as a volcanological tool. The exceptional magnitude and intensity of the Toba eruption is demonstrated by comparison of these data with the deep-sea tephra layers associated with the eruptions of the Campanian ignimbrite, Italy and of Santorini, Greece in Minoan time. The volume of ignimbrite and distal tephra fall deposit produced in the Toba eruption are comparable, a total of at least 1000 km3 of dense rhyolitic magma. In contrast the volume of dense magma produced by the Campanian and Santorini eruptions are approximately 70 and 13 km3 respectively. Thickness versus distance data on the three deep-sea tephra layers show that eruptions of smaller magnitude than Santorini are unlikely to be preserved as distinct tephra layers in most deep-sea cores. In proximal cores all three tephra layers show two distinct units: a lower coarse-grained unit and an upper fine-grained unit. We interpret the lower unit as a plinian deposit and the upper unit as a co-ignimbrite ash-fall deposit, indicating two major eruptive phases. The Toba tephra layer is coarser both in maximum and median grain size than the Campanian and Santorini layers at a given distance from source. These data are interpreted to indicate a very high cruption column, estimated to be at least 45 km. We have applied a method for estimating the duration of the Toba eruption from the style of graded-bedding in deep-sea tephra layers. Studies of two cores yield estimates of 9 and 14 days. The eruption column height and duration estimates both indicate an average volume discharge rate of approximately 106 m3/sec. The Toba eruption therefore was not only of exceptional magnitude, but also of exceptional intensity.
TL;DR: Codium was capable of simultaneously taking up all three forms of inorganic N although the presence of NH4+ reduced the uptake of both NO3‐‐ and NO2‐‐, suggesting part of the ecological success of Codium in a N‐limited environment may be due to its N uptake capabilities.
Abstract: The uptake of nitrate, nitrite and ammonium by Codium fragile subsp. tomentosoides (van Goor) Silva was measured at different combinations of temperature (6–30 C) and irradiance (0–140 μEin.m-2. s-1). Uptake of all three forms of N was greater at 12–24 C than at 6 and 30 C. Although uptake was stimulated by light, saturation occurred at relatively low irradiance (7–28 μEin m-2 s-1, depending on the N source and temperature). The Michaelis-Menten uptake constants (Vmax K)varied with temperature. Vmax was greatest at intermediate temperatures and K was lowest at lower temperatures. The Vmaxfor NH4+ was higher and the K, for NH4+was lower than those for NO3-- and NO2--. Codium was capable of simultaneously taking up all three forms of inorganic N although the presence of NH4+ reduced the uptake of both NO3-- and NO2--. The results of this study indicate that part of the ecological success of Codium in a N-limited environment may be due to its N uptake capabilities.
TL;DR: In this article, the mass of the mantle Cl and Br and the Cl/Br ratio of the oceans is estimated by a model of the Earth's history. But the model assumes that a decreasing rate of mantle cl and Br flux by volcanism throughout the world's history can account for the mass and ratio of oceans.
Abstract: Continuous fluxing at a decreasing rate of mantle Cl and Br by volcanism throughout the Earth's history can account for the mass of Cl and Br, and the Cl/Br ratio, of the oceans.
TL;DR: Analyses of tephra in abyssal piston cores collected during cruises of R/V Trident showed that the Minoan eruption produced at least 28 km3 of tectra (13 km3 dense rock equivalent) as mentioned in this paper.
Abstract: Analyses of tephra in abyssal piston cores collected during cruises of R/V Trident show that the Minoan eruption produced at least 28 km3 of tephra (13 km3 dense rock equivalent). A layer up to 5 cm thick must have been deposited on eastern Crete.
TL;DR: The Mediterranean Sea is a partillay isolated ocean where excess evaporation over precipitation results in large east to west gradients in temperature and salinity as mentioned in this paper, and the distribution of planktonic foraminiferal distributions have been examined in 66 surface sediment samples from the Mediterranean Sea.
TL;DR: In this article, the authors attributed the events in Askja and its lissure swarm to rise of basaltic magma into a high-level reservoir in the central volcano, subsequent rifting of the reservoir and lateral flow magma within the fissures swarm to emerge in the Sveinagja eruption.
Abstract: In 1874 and 1875 the fissure swarm of Askja central volcano was activated during a major rifting episode. This rifting resulted in a fissure eruption of 0.3 km3 basaltic magma in Sveinagja graben, 50 to 70 km north of Askja and subsequent caldera collapse forming the Oskjuvatn caldera within the main Askja caldera. Five weeks after initial collapse, an explosive mixed magma eruption took place in Askja. On the basis of matching chemistry, synchronous activity and parallels with other rifted central volcanoes, the events in Askja and its lissure swarm are attributed to rise of basaltic magma into a high-level reservoir in the central volcano, subsequent rifting of the reservoir and lateral flow magma within the fissure swarm to emerge in the Sveinagja eruption. This lateral draining of the Askja reservoir is the most plausible cause for caldera collpse.
TL;DR: The phase of the molt cycle affects dominance status and the performance of agonistic acts in individual juvenile lobsters (Homarus americanus) and lobsters in the midphase of proecdysis are more aggressive than those in intermolt.
Abstract: The phase of the molt cycle affects dominance status and the performance of agonistic acts in individual juvenile lobsters (Homarus americanus). Lobsters in the midphase of proecdysis are more aggressive than those in intermolt; the latter are more aggressive than lobsters in early or late proecdysis and those in postecdysis.
TL;DR: Findings suggest that violence, well beyond ordinary physical punishment, is an extensive and patterned phenomenon in parent-child relations.
Abstract: This paper reports results of a survey of a representative sample of 2143 American families, designed to examine the incidence, modes, and patterns of parent-to-child violence. Findings suggest that violence, well beyond ordinary physical punishment, is an extensive and patterned phenomenon in parent-child relations. Implications are discussed, and directions for further research are indicated.
TL;DR: This difference in isotopic response suggests that surface-water salinities were drastically reduced during times of sapropel formation, possibly as the result of meltwater runoff from the Fennoscandian ice sheet into the eastern Mediterranean by way of the Black and Aegean seas.
Abstract: Major negative oxygen isotopic anomalies in planktonic foraminifera are associated with deep-sea anoxic mud layers (sapropels) deposited 9000 and 80,000 years ago in the eastern Mediterranean. The isotopic depletion in surface-dwelling foraminifera is significantly greater than in mesopelagic foraminifera. This difference in isotopic response suggests that surface-water salinities were drastically reduced during times of sapropel formation, possibly as the result of meltwater runoff from the Fennoscandian ice sheet into the eastern Mediterranean by way of the Black and Aegean seas.
TL;DR: A simple three-point mixing model involving subtropical surface water, Amazon River water, and North Atlantic tropical rain water indicates that at least 60% of the freshwater in these seasonal salinity depressions originates from the Amazon River as mentioned in this paper.
TL;DR: In this paper, a semipartial correlation to the zero-order correlation is proposed, which can be easily extended from the two predictor case to the general p-predictor case.
Abstract: Since Horst (1941) initially introduced the concept, a number of investigators have suggested alternative definitions that both include a broader class of situations and are more precise. Following a conceptual framework suggested by Conger (1974), the present paper discusses a definition based on the relation of the semipartial correlation to the zero order correlation. This definition possesses a number of advantages, including the fact that it can be easily extended from the two predictor case to the general p-predictor case.
TL;DR: Large numbers of resting spores of Thalassiosira nordenskioeldii Cleve and Detonula confervacea (Cleve) Gran were produced when these species were grown at low levels of ammonia and nitrate, suggesting that these two species appear to be an adaptation for the survival of long periods of darkness in polar regions.
Abstract: Large numbers of resting spores of Thalassiosira nordenskioeldii Cleve and Detonula confervacea (Cleve) Gran were produced when these species were grown at low levels of ammonia and nitrate. The production of resting spores by T. nordenskioeldii was inversely related to temperature. At 0° and 5°C between 68 and 96% of the total cells were resting spores, while at 15°C resting spores were not produced. Resting spores of both species would not survive 7 days in the dark at 20°C. At 0°, 5°, 10° and 15°C, the length of time that the resting spores of both T. nordenskioeldii and D. confervacea remained viable was inversely related to temperature. At 0°C, T. nordenskioeldii remained viable for 576 days. The data suggest that the production of resting spores by these two species does not aid them in the survival of unfavorably high temperatures such as are found in temperate estuaries during the summer. Rather, they appear to be an adaptation for the survival of long periods of darkness in polar regions.
TL;DR: Chlorine and bromine variations in basalts erupted along the Reykjanes Ridge axis and Iceland follow a predicted first-order model, reflecting volatile degassing at water depths shallower than about 500 m, superimposed with changes due to the presence of two chemically distinct mantle sources as mentioned in this paper.
Abstract: Chlorine and bromine variations in basalts erupted along the Reykjanes Ridge axis and Iceland follow a predicted first-order model, reflecting volatile degassing at water depths shallower than about 500 m, superimposed with changes due to the presence of two chemically distinct mantle sources and their mixing. Iceland mantle ‘plume’ contains three to four times more pristine Cl and Br than the asthenosphere depleted in large ionic lithophile elements.