The effects of fire on rock weathering: some further considerations of laboratory experimental simulation

Fire in the natural environment is a widespread agent of geomorphological and biological change. Temperatures can exceed 1000°C. There is often a rapid rise from ambient conditions through a steep thermal gradient, promoting rock disintegration. Laboratory simulation studies have established that temperature changes which are representative of natural fires affect rock material properties, which can then be related to weathering susceptibility. This study extends previous work by more closely replicating the natural environment, (a) through the simulation of rainfall and (b) by encasing samples to reflect the exposure of a single rock face to a passing fire event. Rock samples collected on Cyprus were prepared and tested following previously reported procedures. Change in modulus of elasticity was monitored using a non-destructive ultrasonic method. The data corroborate previous work but with somewhat different degrees of change. The new results are more likely to be representative of natural conditions and real-world change. The rate of rock disintegration and effects such as case-hardening appear to be a function of rock thermal characteristics, material properties and environmental constraints such as diurnal temperature range. Copyright © 1999 John Wiley & Sons, Ltd.     

The effect of tidal forcing on biogeochemical processes in intertidal salt marsh sediments

Background  

Early diagenetic processes involved in natural organic matter (NOM) oxidation in marine sediments have been for the most part characterized after collecting sediment cores and extracting porewaters. These techniques have proven useful for deep-sea sediments where biogeochemical processes are limited to aerobic respiration, denitrification, and manganese reduction and span over several centimeters. In coastal marine sediments, however, the concentration of NOM is so high that the spatial resolution needed to characterize these processes cannot be achieved with conventional sampling techniques. In addition, coastal sediments are influenced by tidal forcing that likely affects the processes involved in carbon oxidation.     

Charting the territory: Exploring stakeholder reactions to the prospect of seafloor exploration and mining in Australia

Geological surveys of Australia’s marine territory have revealed significant potential for development of a marine resource industry. As onshore mineral deposits become harder to find, less accessible to their market and more challenging to extract, seafloor exploration and mining becomes an economically viable option. However, evidence from industry and environmental literature suggests that social acceptance will be important in determining the future of this industry in Australia. This paper reports on findings from research investigating the social viability of seafloor mining in Australia. A combination of interviews and focus groups were used to explore industry and community reactions to the possible development of seafloor mining in Australia. Although stakeholders’ reactions were variable, the majority of the participants were reluctant to see development of seafloor mining in Australia, primarily because of concerns about the industry’s potential environmental impact. All stakeholders sought further information about the benefits and costs associated with the industry suggesting that they did not yet have a fixed attitude towards the industry. Stakeholders favoured a precautionary approach towards the industry, supported by rigorous scientific analysis of the potential environmental impacts, transparent and socially responsive management processes and meaningful engagement with stakeholders.     

Observations of the supernova SN1987L with the new Faint Object Spectrograph on the 4.2 m William Herschel Telescope

We present the spectrum of the supernova SN1987L in NGC 2336 over the wavelength range 4000–9700 Å as recorded in one 500 s exposure on 20–21 October, 1987. This spectrum was taken using the new Faint Object Spectrograph on the 4.2 m William Herschel Telescope (WHT) at the Observatorio del Roque de los Muchachos.We conclude that SN1987L was a type Ia supernova, and approximately 100 days post maximum at the time of the observation.     

Movement of a small slipfaceless dome dune in the Namib Sand Sea, Namibia

The migration of a small slipfaceless dome dune close to the northern edge of the Namib Sand Sea has been measured by topographic survey. The dune dimensions are 45-m wide and 1-m high with a volume of 551 m³ that has been calculated as the difference between the dune's surface elevation and an interdune surface extrapolated from measurements around the edge of the dune. The migration direction, 64°, and distance moved, 90 m, are measured against stakes set out in 1976. The dune has moved about 90 m between 1976 and 1999. This is an average linear migration rate of around 4 m year⁻¹, and is equivalent to an annual sand transport rate of about 1.2 tonnes m⁻¹ year⁻¹. The calculated total potential sand flow in this part of the Namib Desert is 119 tonnes m⁻¹ year⁻¹, and the resultant potential sand flow is 63 tonnes m⁻¹ year⁻¹. The dune migration is therefore about 1% of the total potential sandflow and 2% of the resultant indicating that dune migration is only a small part of total potential sand transport. The results suggest that small slipfaceless dome dunes are very inefficient at trapping sand, and that winds blowing across the interdune in this area are undersaturated with sand.     

An excerpt of X‐shooter operations at Paranal

We report on the current performances and measurements done with X‐shooter during its first year of operations at Paranal. We present the current instrumental problems, recent and future improvements, and give advice for the observations (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ensemble properties of comets in the Sloan Digital Sky Survey

We present the ensemble properties of 31 comets (27 resolved and 4 unresolved) observed by the Sloan Digital Sky Survey (SDSS). This sample of comets represents about 1 comet per 10 million SDSS photometric objects. Five-band (u, g, r, i, z) photometry is used to determine the comets’ colors, sizes, surface brightness profiles, and rates of dust production in terms of the Afρ formalism. We find that the cumulative luminosity function for the Jupiter Family Comets in our sample is well fit by a power law of the form N(<H) ∝ 10^{(0.49±0.05)H} for H < 18, with evidence of a much shallower fit N(<H) ∝ 10^{(0.19±0.03)H} for the faint (14.5 < H < 18) comets. The resolved comets show an extremely narrow distribution of colors (0.57 ± 0.05 in g ? r for example), which are statistically indistinguishable from that of the Jupiter Trojans. Further, there is no evidence of correlation between color and physical, dynamical, or observational parameters for the observed comets.     

Origin of a complex and spatially diverse dune-field pattern, Algodones, southeastern California

The Algodones Dune Field of southeastern California shows a complex and spatially diverse dune-field pattern that is superimposed upon a series of topographic lineations. Analysis of dune-field pattern parameters (dune crest length, crest orientation, dune spacing and defect density) derived from aerial images indicates that the dune-field pattern represents two constructional generations. Prominent compound crescentic dunes formed during the first constructional generation. A younger generation consists of a variety of simple crescentic dunes, linear dunes and zibars. Statistical differences in the pattern parameters between the dune groups within the second generation are resolved through consideration of the boundary conditions under which the dune pattern evolved, and provide explanations for: (1) diversity of dune types, (2) range in implied constructional times, (3) range in crest orientations, and (4) the anomalous nature of the population of linear dunes. The boundary conditions that have modified pattern development include orographic effects, grain size, vegetation, areal extent and antecedent conditions. Topographic lineations in the Algodones range from the Western Ramp, which defines the field margin, to subtle features masked by the pattern of dunes. Imaging of the Western Ramp using Ground Penetrating Radar shows high-angle cross-strata migrating perpendicular to the lineation trend. The most plausible hypothesis for the origin of the lineations is as dune ridges sequentially shed from adjacent Lake Cahuilla, which is the source of Algodones sands. The overall geomorphic complexity of the Algodones originates from the emplacement of the dune ridges during stages of Lake Cahuilla, the two generations of dune-field construction, and the controls exerted by boundary conditions.