Results of the solar constant experiment onboard Spacelab 1

A cavity type absolute radiometer was flown on Spacelab 1 in December 1983. We obtain a value of the solar constant of 1361.5 W m^–2 with an estimated accuracy of ±2.3 W m^–2 or 0.17%. When comparing this with other recent determinations, we find discrepancies which we consider indicative of metrological problems in present day absolute radiometry.     

Contemporary ocean and coastal management issues in Australia and New Zealand: an overview

The past decade has witnessed an unprecedented increase in the number of international treaties, conventions and agreements dealing with maritime issues and oceans governance. Most nations are attempting to cope with this expanding agenda at a time of fiscal constraint, competing environmental demands and the emergence of a new global strategic, political and economic order. However, similar issues do not always lead to similar outcomes. Australia and New Zealand share some common oceanic and coastal management problems, but variations in response arise from geographical differences, constitutional provisions, political style and administrative arrangements. This paper provides a brief overview of contemporary maritime issues and attempted solutions in both nations.     

Late Pleistocene to Holocene sedimentation and hydrocarbon seeps on the continental shelf of a steep,tectonically active margin,southern California,USA

Small, steep, uplifting coastal watersheds are prolific sediment producers that contribute significantly to the global marine sediment budget. This study illustrates how sedimentation evolves in one such system where the continental shelf is largely sediment-starved, with most terrestrial sediment bypassing the shelf in favor of deposition in deeper basins. The Santa Barbara–Ventura coast of southern California, USA, is considered a classic area for the study of active tectonics and of Tertiary and Quaternary climatic evolution, interpretations of which depend upon an understanding of sedimentation patterns. High-resolution seismic-reflection data over >570 km² of this shelf show that sediment production is concentrated in a few drainage basins, with the Ventura and Santa Clara River deltas containing most of the upper Pleistocene to Holocene sediment on the shelf. Away from those deltas, the major factor controlling shelf sedimentation is the interaction of wave energy with coastline geometry. Depocenters containing sediment 5–20 m thick exist opposite broad coastal embayments, whereas relict material (bedrock below a regional unconformity) is exposed at the sea floor in areas of the shelf opposite coastal headlands. Locally, natural hydrocarbon seeps interact with sediment deposition either to produce elevated tar-and-sediment mounds or as gas plumes that hinder sediment settling. As much as 80% of fluvial sediment delivered by the Ventura and Santa Clara Rivers is transported off the shelf (some into the Santa Barbara Basin and some into the Santa Monica Basin via Hueneme Canyon), leaving a shelf with relatively little recent sediment accumulation. Understanding factors that control large-scale sediment dispersal along a rapidly uplifting coast that produces substantial quantities of sediment has implications for interpreting the ancient stratigraphic record of active and transform continental margins, and for inferring the distribution of hydrocarbon resources in relict shelf deposits.     

Observations of Coronal Mass Ejections with the Coronal Multichannel Polarimeter

The Coronal Multichannel Polarimeter (CoMP) measures not only the polarization of coronal emission, but also the full radiance profiles of coronal emission lines. For the first time, CoMP observations provide high-cadence image sequences of the coronal line intensity, Doppler shift, and line width simultaneously over a large field of view. By studying the Doppler shift and line width we may explore more of the physical processes of the initiation and propagation of coronal mass ejections (CMEs). Here we identify a list of CMEs observed by CoMP and present the first results of these observations. Our preliminary analysis shows that CMEs are usually associated with greatly increased Doppler shift and enhanced line width. These new observations provide not only valuable information to constrain CME models and probe various processes during the initial propagation of CMEs in the low corona, but also offer a possible cost-effective and low-risk means of space-weather monitoring.     

Modeling of the swelling–shrinkage behavior of expansive clays during wetting–drying cycles

Acta Geotechnica - This paper presents a constitutive model for simulating the swelling–shrinkage volume change of expansive soils during wetting–drying cycles. Based on the concept of...     

Quaternary sea level fluctuations on a tectonic coast: New 230Th234U dates from the Huon Peninsula,New Guinea

Emerged coral reef terraces on the Huon Peninsula in New Guinea were reported in a reconnaissance dating study by Veeh and Chappell 1970. Age definition achieved was not good for several important terraces, and we report here a series of new ${}^{230}\text{Th}{}^{234}\text{U}$ dates, which further clarify the history of late Quaternary eustatic sea level fluctuations. More than 20 reef complexes are present, ranging well beyond 250,000 yr old: we are concerned with the seven lowest complexes. Major reef-building episodes dated by ${}^{30}\text{Th}{}^{234}\text{U}$ are reef complex I at 5–9 ka (kilo anno = 1000 yr), r.c. IIIb at 41 ka (four dates), r.c. IV at 61 ka (four dates), r.c. V at 85 ka (two dates), r.c. VI at 107 ka (two dates), and r.c. VII at 118–142 ka. Complex II was previously dated by ¹⁴C at 29 ka: this age has not yet been confirmed, and may be only a lower limit. The reef crests were built during or immediately before intervals of sea level maxima, when rates of rising sea level and tectonic uplift briefly coincided. The culmination of each reef-building episode was only a few thousand years in duration, and multiple dates from the same reef complex generally group within the statistical errors of the individual dates.Several methods can be used to estimate the altitude of each sea level maximum relative to present sea level. The least complicated is to calculate mean tectonic uplift rate for each profile of the terraces, and use the mean rate to calculate the tectonic displacement of each dated reef complex on that profile. The difference between the present altitude of a reef complex and its calculated tectonic uplift gives the paleosea level at the time the reef grew. We estimate uplift rates for six surveyed sections by calibrating against published paleosea level estimates from Barbados and elsewhere, viz 125 ka, paleosea at +6 m; 103 ka, ?15 m; 82 ka, ?13 m. For each section the individual uplift rates for reefs V, VI, and VIIb are within 5% of their section means. Using the mean rates. paleosea level estimates for reef crests II, IIIB, and IV are made for each section. Consistency of estimates between sections is good, giving ?28 m for the 60 ka paleosea level, around ?38 m for the 42 ka level and ?41 m for the 28 ka level (if the age is older the paleosea level would be lower. Using the mean uplift rates, the 82 ka and 103 ka paleosea levels are also estimated for each section: all individual estimates are plotted graphically, and a sea level curve drawn. The reef stratigraphy indicates sea level lowerings between each dated reef crest: the crests probably represent the interstadials of the Wisconsin (Würm, Weichsel) Glaciation, and intervening lower levels correspond to stadials. Since the last time of eustatic sea level higher than the present (about 125 ka), five sea level maxima occurred at roughly 20-ka intervals, none being as high as the present.     

Geochemistry and Intrusive History of the Ashland Pluton, Klamath Mountains, California and Oregon

The Ashland pluton is a calc-alkaline plutonic complex thatintruded the western Paleozoic and Triassic belt of the KlamathMountains in late Middle Jurassic time. The pluton comprisesa series of compositionally distinct magma pulses. The oldestrocks are hornblende gabbro and two-pyroxene quartz gabbro withinitial ⁸⁷Sr/⁸⁶Sr = 0{dot}7044, ¹⁸O = 8{dot}7%, and REE patternswith chondrite normalized La/Lu = 7. These units were followedby a suite of tonalitic rocks (La_N/Lu_N = 7) and then by a suiteof K₂O- and P₂O₅ rocks of quartz monzodioritic affinity (La_N/Lu_N= 13–21; La_N/Sm_N = 2{dot}4–3{dot}) The quartz monzodioriticrocks were then intruded by biotite granodiorite and granitewith lower REE abundances but more fractionated LREE(La_N/Lu_N= 13–19; La_N/Sm_N = 4{dot}3–6 and they, in turn,were host to dikes and bosses of hornblende diorite. The latestintrusive activity consisted of aplitic and granitic dikes.Combined phase equilibria and mineral composition data, indicateemplacement conditions of approximately P_total = 2{dot}3kb,P_H2O between 1{dot}5 and 2{dot}2 kb, and f_O2 between the nickel-nickeloxide and hematite-magnetite buffers. Successive pulses of magma display increasing SiO₂ togetherwith increasing ¹⁸O and decreasing initial ⁸⁷Sr/⁸⁶Sr. The isotopicdata are consistent with either (1) combined fractional crystallizationof andesitic magma and concurrent assimilation of crustal materialcharacterized by low Sr₁ and high (¹⁸O or, more probably, (2)a series of partial melting events in which sources were successivelyless radiogenic but richer in ¹⁸O Each intrusive stage displaysevidence for some degree of crystal accumulation and/or fractionalcrystallization but neither process adequately accounts fortheir compositional differences. Consequently, each stage appearsto represent a distinct partial melting or assimilation event. The P₂O₅-rich nature of the quartz monzodiorite suite suggestsaccumulation of apatite. However, the suite contains abundantmafic microgranitoid enclaves and most apatite in the suiteis acicular. These observations suggest that magma mixing affectedthe compositional variation of the quartz monzodiorite suite.Mass balance calculations are consistent with a simple mixingprocess in which P₂O₅-rich alkalic basalt magma (representedby the mafic microgranitoid enclaves) was combined with a crystal-poorfelsic magma (represented by the tonalite suite), yielding aquartz monzodioritic magma that then underwent differentiationby crystal fractionation and accumulation.     

Environmental Factors Contributing to the Development and Demise of a Toxic Dinoflagellate (<Emphasis Type="Italic">Karlodinium veneficum</Emphasis>) Bloom in a Shallow,Eutrophic, Lagoonal Estuary

A dense bloom of the ichthyotoxic dinoflagellate Karlodinium veneficum was discovered in the Neuse River Estuary, North Carolina, on 19 October 2006 and was associated with four subsequent fish kills. Microscopic, photopigment, DNA, and toxicological techniques confirmed bloom identity and toxicity. High-resolution spatio-temporal data from ship-board and fixed automated sampling stations provided a unique opportunity to investigate the environmental conditions that initiated, maintained, and terminated the K. veneficum bloom. Bloom initiation and growth were favored by high nutrient availability and reduced dispersal during the period of declining riverine discharge after Tropical Storm Ernesto. K. veneficum out-competed other co-occurring dinoflagellates, perhaps because of the production of karlotoxins that are known to act as grazing deterrents and to facilitate mixotrophic feeding. Once the bloom was established, small-scale hydrodynamic processes, coupled with vertical migration, concentrated cells along a frontal convergence to high densities (>200,000 cells per milliliter). By 26 October 2006, wind mixing and possible nutrient stress disrupted the bloom. Release of cell-bound toxins during the bloom collapse likely accounted for the associated fish kill events where fish were reported as exhibiting typical symptoms of karlotoxin poisoning. The dynamics of this bloom underscore the tight control of harmful algal blooms by meteorological forcing, hydrology, and sediment nutrient input in this shallow lagoonal estuary.     

GIS in the K-12 Curriculum: A Cautionary Note

Two qualitative case studies, one focusing on K-12 teachers and the other on middle school students, explore key factors associated with using Geographic Information Systems in the classroom. In both studies, access to appropriate hardware is a critical barrier. Time is another critical barrier—time to learn the GIS software and time in the curriculum to incorporate GIS as a learning experience. In both case studies, learning the technology at the expense of learning spatial analysis was a danger, suggesting the need for conscious focus on the goal of using GIS to learn how to “do geography.”