Evolution of alkalic lavas at Haleakala Volcano,east Maui,Hawaii

The postshield and posterosional stages of Haleakala Volcano contain intercalated alkalic basalt and evolved alkalic lavas. Isotopic and incompatible element abundance ratios in the Haleakala postshield basalts changed systematically with time, providing evidence for significant temporal changes in the mantle components contributing to the magmatic sources. Specifically, a depleted, i.e. low⁸⁷Sr/⁸⁶Sr and high¹⁴³Nd/¹⁴⁴Nd, mantle component is more abundant in younger lavas. However, as magma-production rates decreased during the postshield and posterosional stages, basaltic melts in magma reservoirs cooled and fractionated, leading to evolved residual melts such as hawaiite. Because primary basalt compositions changed with time, the evolved Haleakala lavas formed from a range of parental compositions. However, basalts and evolved lavas of similar age and isotopic ratios (Sr and Nd) have major and trace element contents that are consistent with a crystal-fractionation model. Although alkalic basalt and hawaiite are the dominant lavas of the postshield stages of both Haleakala and Mauna Kea volcanoes, there are important differences between their lavas. For example, compositional differences between the hawaiite suites at Haleakala and Mauna Kea indicate that, on average, the evolved lavas at Haleakala formed at lower pressures. Also, at Haleakala basalts are intercalated with hawaiites, whereas at Mauna Kea basalts and hawaiites are separated by a sharp boundary. These differences probably reflect a higher magma supply rate to the Haleakala volcano.     

INTERPRETING THE LARGE LIMB ERUPTION OF JULY 9, 1982

A time series of K3 spectroheliograms taken at the Coimbra Observatory exhibits an erupting loop on the east limb on July 9, 1982 in active region NOAA 3804. The Goddard SMM Hard X-Ray Burst Spectrometer (HXRBS) observations taken during this period reveal a hard X-ray flare occurring just before the loop eruption is observed, and SMS-GOES soft X-ray observations reveal a strong long-duration event (LDE) following the impulsive phase of the flare. A Solwind coronagram exhibits a powerful coronal mass ejection (CME) associated with the erupting loop. H flare and prominence observations as well as centimeter and decimeter radio observations of the event are also reviewed. A large, north–south-oriented quiescent prominence reported within the upper part of the CME expansion region may play a role in the eruption as well. The spatial and temporal correlations among these observations are examined in the light of two different current models for prominence eruption and CME activation: (1) The CME is triggered by the observed hard X-ray impulsive flare. (2) The CME is not triggered by a flare, and the observed soft X-ray flare is an LDE due to reconnection within the CME bubble. It is concluded that this event is probably of a mixed type that combines characteristics of models (1) and (2). The July 9 event is then compared to three other energetic CME and flare eruptions associated with the same active-region complex, all occurring in the period July 9 through September 4, 1982. It is noted that these four energetic events coincide with the final evolutionary phase of a long-lasting active-region complex, which is discussed in a companion paper (Bumba, Garcia, and Jordan, 1997). The paper concludes by addressing the solar flare myth controversy in the light of this work.     

Decomposition and analysis by atomic absorption photospectrometry of silicate rocks

A rapid and simple method of analysis of silicate rocks using gold crucibles and fluoroboric acid as a solvent of the disintegrated material has been developed. The main elements are determined in a single treatment. The results obtained are comparable to the values recommended for samples of eleven standard rocks.     

Time series surface-wave recovery from pressure gage

Recovery of surface-wave time series from pressure gage data is a time-consuming process and is not customarily carried out. Such information is, however, useful particularly in real-time for warning of freak waves or waves of unusual characteristics. Two simple numerical filters are developed here to serve such purpose. The first method is a linear filter with a built-in window to suppress high-frequency noise. The second method recovers the surface wave by computing the local surface curvature. These filters are very simple and can be programmed into a microprocessor to be integrated into field instrument packages.Both filters have been tested satisfactorily against conventional linear filters using simulated wave data and wave data collected in intermediate water depth. Neither filter requires pre-filtering of noise from raw data, which is commonly required to recover surface-wave information from sub-surface pressure data.     

Sediment distribution patterns on the Galicia-Minho continental shelf

A sedimentological and bathymetric study of the Minho-Galicia Shelf shows a strong contrast between a southern shelf region with a thin partially relict cover of sands and gravel, and a northern region where fine-grained sediments predominate. This contrast is explained through differences in the sediment supply, the oceanographic environment (storms and ocean currents) and the morphology of the shelf which results from its underlying tectonic framework.Most sediment is supplied to the Galicia-Minho Shelf by river discharges onto the Minho Shelf, particularly that from the Douro River. In the northern part of the shelf the Galician Rías act as sediment traps rather than sediment suppliers. The bulk of the sediment washes out of the rivers during episodic storm events. While most of the coarse sediments remain deposited close to the coast, the fine-grained material is exported to the outer areas of the shelf. Subsequently, coarse sediments close to the coast are transported southwards by the littoral drift. Whereas the fine-grained material is frequently resuspended through the action of the large swells who influence reaches deep into the water. This frequent resuspension has a long-term sorting effect on the sediments. Furthermore, resuspended sediments on the middle and outer regions of the shelf are transported northwards by a poleward flowing bottom current.As a consequence of the differential transport of coarse sediments to the south, and of the fine-grained sediments to the north, the outer reaches of the Minho Shelf are relatively poor in recent sediments. In many areas relict sediments as well as features associated with ancient coastlines and river mouths, still appear as seabed features. In contrast, the northern regions of the shelf are covered by a thin veneer of fine-grained material that smooth other most of these fossil features.The fine-grained sediment fractions (mostly very fine sands to coarse silts) are deposited in two large mud patches, the Douro and the Galicia Mud Patches, which are situated at water depths of around 100–120 m. These two mud patches are both controlled by the local hydrodynamics and morphology. The Beiral de Viana, to the west of the Douro Mud Patch is a plateau, up to 20 m high lying parallel to the shelf-break and is a morphological expression of an underlying horst system. This plateau acts as a barrier that prevents the drift of some of the fine-grained material to the west, out over the shelf-break and the continental slope. The Galicia Mud Patch is situated on the eastern part of the Galician Shelf to the north of the Douro Mud Patch. It is situated near the extension of the Porto–Tomar fault, which results in the shelf being usually steep in this region, down to a depth of about 100 m. West of this area the slope is much more gentle. Northward transport of the sediment is strongly reduced by the E–W trending outcrops of plutonic and metamorphic rocks.     

Mediterranean Marine Reserves: Fish Indices as Tests of Protection Efficiency

Abstract. The fish assemblages of a strictly protected area and of a neighbouring fished area, located off a Mediterranean urbanized coast (Carry-le-Rouet, France), were compared in order to select the most evident, constant, and easily recorded indices of the 'reserve effect'. Visual censusing was repeated simultaneously at both sites eight time a year during 3 years along four permanent transects layed on shallow rocky bottoms (9–14 m). Overall species richness was 16% higher in the reserve, but differences in average instantaneous richness were only marginally significant. The most contrasting results were shown by the occurrence frequency, abundance, and demographic structure of two types of target species. The type A target species group comprises 16 large meso- and macrocarnivores particularly threatened by spearfishing, including the common nectobenthic sparids Diplodus spp. Type B target species are represented by two small territorial fishes particularly impacted by angling: the serranid Serranus cabrilla and the terminal phase males of the labrid Coris julis . The size structure of Diplodus spp., S. cabrilla , and C.julis subpopulations strongly argues for the role of protected areas as a reservoir of large spawners. Fishing pressure is assumed to modify the social conditions of the C. julis local populations and to induce earlier sex change.     

A phytoplankton class-specific primary production model applied to the Kerguelen Islands region (Southern Ocean)

As part of the KErguelen: compared study of the Ocean and the Plateau in Surface water (KEOPS) project in late summer 2005, we examine the phytoplankton community composition and associated primary production in the waters surrounding the Kerguelen Archipelago, with the emphasis on two contrasted environments: (i) the Kerguelen Plateau, where a large bloom occurs annually, and (ii) the high-nutrient low-chlorophyll (HNLC) offshore waters. A biomarker pigment approach was used to assess the community composition in terms of chlorophyll biomass of three phytoplankton size classes, namely micro-, nano-, and picophytoplankton. The second objective was to evaluate a global class-specific approach for estimating the contribution of the three pigment-based size classes to the primary production in the study area. To do so, primary production rates associated with each phytoplankton class were computed from the class-specific chlorophyll biomass coupled to a class-specific primary production model, and compared with in situ measurements of size-fractionated ¹³C-based primary production. The iron-enriched bloom region was dominated by microphytoplankton (diatoms), which contributed 80–90% to the total primary production (of ≈1 g C m^?2 d^?1). In the HNLC area, the primary production was about 0.30 g C m^?2 d^?1, mainly (65%) achieved by small diatoms and nanoflagellates. The model results show a good overall agreement between predicted and measured total primary production rates. In terms of size classes, agreements were higher for the bloom region than for the HNLC waters. Discrepancies in this complex iron-limited area may be explained essentially by the smaller size of diatoms, or a different set of photophysiological properties.