Long-lived Coronal Loop Profiles from TRACE

An initial study of long-lived loops observed with TRACE (Lenz et al., 1999) shows that they have no significant temperature stratification and that they are denser than the classic loop model predicts. Models that agree better with the observations include a loop consisting of a bundle of filaments at different temperatures and a loop with momentum input by MHD waves. Some implications for coronal heating models and mechanisms are discussed.     

Consolidation-related fabric changes of periplatform sediments

Geotechnical properties of carbonate sediments result from several factors such as the particular constituents comprising the sediment, the mineralogy, fabric, and effective stress. Investigating the effects of increasing effective stress by mechanical consolidation using permeability, porosity, and porometry determinations reveals fabric changes that could not be determined in scanning electron micrographs. Porometry changes, determined using an image analyzer, are a function of matrix composition and grain support. Samples that were predominantly matrix-supported exhibited an increase in pore numbers per unit area and a pore size decrease resulting from consolidation. Samples composed predominantly of aragonite needle matrices displayed opposite behavior.     

Analysis of long- and short-term temporal variations of the diffuse CO2 emission from Timanfaya volcano,Lanzarote, Canary Islands

Reported herein are the results of eight soil CO₂ efflux surveys performed from 2006 to 2011 at Timanfaya Volcanic Field (TVF), Lanzarote Island with the aim of evaluating the long- and short-term temporal variations of the diffuse CO₂ emission. Soil CO₂ efflux values ranged from non-detectable up to 34.2 g m⁻² d⁻¹, with the highest values measured in September 2008. Conditional sequential Gaussian simulations (sGs) were applied to construct soil CO₂ efflux distribution maps and to estimate the total CO₂ output from the studied area at the TVF. Soil CO₂ efflux maps showed a high spatial and temporal variability. Total CO₂ emission rates ranged between 41 and 518 t d⁻¹, February 2011 (winter) being the season when maximum diffuse CO₂ emission rates were observed. To investigate the influence of external variables on the soil CO₂ efflux, a geochemical station (LZT01) was installed at TVF to measure continuously the soil CO₂ efflux between July 2010 and March 2012 Since external factors such as barometric pressure, rainfall, soil water content, soil and air temperatures, and wind speed influence strongly the observed soil CO₂ effluxes, multiple regression analysis was applied to the time series recorded by the automatic geochemical station LZT01 to remove the contribution of these external factors. The influence of meteorological variables on soil CO₂ efflux oscillations accounts for 13% of total variance, with barometric pressure, rainfall and/or soil water content having the most influence in the control of the soil CO₂ efflux. These observations along with the results from the eight soil gas surveys performed at TVF indicate that the short and long-term trends in the diffuse CO₂ degassing are mainly controlled by environmental factors.     

Scale-dependent physical and geoacoustic property variability of shallow-water carbonate sediments from the Dry Tortugas, Florida

 Spatial variability of shallow-water carbonate sediments near Dry Tortugas, Florida, is scale-dependent. Wet bulk density, grain density, porosity, compressional wave velocity, and grain size variability generally increase down to 2.4 m vertically and 850 m laterally. Grain size is most variable, followed by porosity, wet bulk density, compressional wave velocity, and grain density bothvertically and laterally, consistent with Walther’s Law. Variability was empirically modeled by linear regression analysis to predict variability based on scale, characterize sediment property variability, and quantify sedimentisotropy.     

Grain-size end-members and environmentally sensitive grain-size components: A comparative study in the mud shelf depocenters off southern Brazil

The current study aims to do a comparative analysis of the results obtained with two End-Member(EM)grain-size modeling techniques(AnalySize and BasEMMA)and the Environmental Sensitive Grain-Size(ESGS)modeling for sediment samples collected in the mudbelts of the southern Brazilian shelf.The methods were compared using grain-size data from the south Brazilian shelf,and the results are discussed here.It is the first time that the concept of ESGS,in its present form,is utilized outside China.The results show that despite its relative ease of use,the ESGS is not fully comparable to the EM analyses,and only two grain-size ESGS classes were recognized as analogous to EMs.The comparison of the AnalySize and BasEMMA procedures also revealed significant differences between the techniques.A comparative analysis between the two EM techniques revealed advantages in the BasEMMA,especially in the better correlation of the end-members with the original grain size distribution.The analysis of the geographical distribution of the EM abundances allowed point sources of sandy populations to be recognized as well as the contribution of the Rio de la Plata as a source of silty sediments to be inferred.     

Marine Geomorphology in the Design of Marine Reserve Networks

Marine environments, key life-support systems for the earth, are under severe threat. Issues associated with managing these common property resources are complex and interrelated. Networks of marine reserves can be valuable for mitigating threats to marine systems, yet the successful design and implementation of such networks has been limited. Efficient ways to conserve marine environments are urgently needed. This Focus Section of The Professional Geographer explores the development of marine reserve networks based on geomorphology, fish biology, ecological connectivity, and appropriate governance. The articles in this Focus Section offer examples of the following: (1) distinctive reef geomorphology dictating the spawning locations of reef fishes, which in turn serve as critical source sites for the replenishment of distant reefs by means of larval transport; (2) an example of a simplified oceanographic model that predicts larval transport from fish breeding sites to important nursery areas; and (3) a case study of the development of a marine reserve network that illustrates key elements of a successful strategy. In sum, this Focus Section offers case studies that show the value of marine geomorphology, oceanographic connectivity, and stakeholder involvement as key elements of multidisciplinary geographic studies applied to the design of marine reserve networks. Geographers can further contribute to the conservation and management of coastal and marine ecosystems in many ways that involve subdisciplines of remote sensing and geographic information systems, political and economic geography, political ecology, and ethnography.