Origin of continental margin morphology: Submarine-slide or downslope current-controlled bedforms, a rock magnetic approach

Morphological features observed in both swath bathymetry and seismic reflection data are not unique, which introduces uncertainty as to their origin. The origin of features observed in the Humboldt Slide has generated much controversy because the same features have been interpreted as a submarine failure deposit versus current-controlled sediment waves. It is important to resolve this controversy because similar structures are observed on many continental margins and the origin of these features needs to be understood. Anisotropy of magnetic susceptibility (AMS) measurements on sediment samples acquired from the Humboldt Slide reveal that the top  8 m have not experienced post-depositional deformation. This suggests that these features are formed by primary deposition associated with downslope currents. Using the same AMS technique on a core acquired north of the Humboldt Slide in a region with no geophysical evidence for post-depositional deformation, we were able to identify a  1 m thick deposit that appears to be a small slump.     

Origin of grain size spectra of suspension deposited sediment

Hydronamic modification by settling from a turbulent suspension of an originally unsorted sediment produces grain size distributions that correspond to the size characteristics of many natural suspended and bottom sediments. Evaluation of the resulting equations allows parameterization of sediments in terms of three constants describing the source material, transport energy, and reworking history, respectively.     

Governance of tuna industries: The key to economic viability and sustainability in the Western and Central Pacific Ocean

The Western and Central Pacific Ocean (WCPO) tuna fishery is an important global food resource, and the economies of many Pacific Islands Countries (PICs) rely heavily on tuna industries. This paper proposes that governance by PICs is the key to improving the sustainability and profitability of tuna industries in the region. ‘Governance’ is usually used to refer to corruption, but here is interpreted more broadly to encompass the whole process by which decisions regarding public life are made and enacted, by government and also civil society. Argument is supported by empirical material from an interview study with stakeholders and a survey of reports.     

Testing the public’s response to receiving severe flood warnings using simulated cell broadcast

Natural Hazards - European Governments must implement a public alerting system to reach mobile phone users affected by major emergencies and disasters by June 2022. Cell Broadcast is used to issue...     

High Plains groundwater isotopic composition in northeastern New Mexico (USA): relationship to recharge and hydrogeologic setting

Hydrogeology Journal - In the High Plains (HP) region of northeastern New Mexico (NE NM), USA, underlying bedrock aquifers are utilized where the High Plains Aquifer is thin, absent, or...     

The Taurewa Eruptive Episode: evidence for climactic eruptions at Ruapehu volcano, New Zealand

 The ca. 10,500 years B.P. eruptions at Ruapehu volcano deposited 0.2–0.3 km³ of tephra on the flanks of Ruapehu and the surrounding ring plain and generated the only known pyroclastic flows from this volcano in the late Quaternary. Evidence of the eruptions is recorded in the stratigraphy of the volcanic ring plain and cone, where pyroclastic flow deposits and several lithologically similar tephra deposits are identified. These deposits are grouped into the newly defined Taurewa Formation and two members, Okupata Member (tephra-fall deposits) and Pourahu Member (pyroclastic flow deposits). These eruptions identify a brief (<ca. 2000-year) but explosive period of volcanism at Ruapehu, which we define as the Taurewa Eruptive Episode. This Episode represents the largest event within Ruapehu's ca. 22,500-year eruptive history and also marks its culmination in activity ca. 10,000 years B.P. Following this episode, Ruapehu volcano entered a ca. 8000-year period of relative quiescence. We propose that the episode began with the eruption of small-volume pyroclastic flows triggered by a magma-mingling event. Flows from this event travelled down valleys east and west of Ruapehu onto the upper volcanic ring plain, where their distal remnants are preserved. The genesis of these deposits is inferred from the remanent magnetisation of pumice and lithic clasts. We envisage contemporaneous eruption and emplacement of distal pumice-rich tephras and proximal welded tuff deposits. The potential for generation of pyroclastic flows during plinian eruptions at Ruapehu has not been previously considered in hazard assessments at this volcano. Recognition of these events in the volcanological record is thus an important new factor in future risk assessments and mitigation of volcanic risk at Tongariro Volcanic Centre. Received: 5 July 1998 / Accepted: 12 March 1999     

Entanglements of marine mammals and seabirds in central California and the north-west coast of the United States 2001-2005

Entanglement records for seabirds and marine mammals were investigated for the period 2001-2005. The entanglement records were extracted from databases maintained by seven organizations operating along the west coast of the United States of America. Their programmes included beach monitoring surveys, rescue and rehabilitation and regional pinniped censuses. Records of 454 entanglements were documented in live animals and in carcasses for 31 bird species and nine marine mammal species. The most frequently entangled species were Common Murres, Western Gulls and California sea lions. The entanglement materials identified were primarily fishing related. Entanglements were recorded every year suggesting that although the incidence level differs annually, entanglement is a persistent problem. It is recommended that each programme records details in standardized categories to determine entanglement material sources. Numbers of entanglements observed during these surveys are likely to be a conservative view of the actual entanglement rate taking place at sea.     

The role of vegetation in the retention of fine sediment and associated metal contaminants in London's rivers

Many urban rivers receive significant inputs of metal‐contaminated sediments from their catchments. Restoration of urban rivers often creates increased slack water areas and in‐channel vegetation growth where these metal‐contaminated sediments may accumulate. Quantifying the accumulation and retention of these sediments by in‐channel vegetation in urban rivers is of importance in terms of the planning and management of urban river restoration schemes and compliance with the Water Framework Directive. This paper investigates sediment properties at four sites across three rivers within Greater London to assess the degree to which contaminated sediments are being retained. Within paired restored and unrestored reaches at each site, four different bed sediment patch types (exposed unvegetated gravel, sand, and silt/clay (termed ‘fine’) sediments, and in‐channel vegetated sediments) were sampled and analysed for a range of metals and sediment characteristics. Many samples were found to exceed Environment Agency guidelines for copper (Cu), lead (Pb) and zinc (Zn) and Dutch Intervention Values for Cu and Zn. At all sites, sediments accumulating around in‐channel vegetation were similar in calibre and composition to exposed unvegetated fine sediments. Both bed sediment types contained high concentrations of pseudo‐total and acetic acid extractable metal concentrations, potentially due to elevated organic matter and silt/clay content, as these are important sorbtion phases for metals. This implies that the changed sediment supply and hydraulic conditions associated with river restoration may lead to enhanced retention of contaminated fine sediments, particularly around emergent plants, frequently leading to the development of submerged and emergent landforms and potential river channel adjustments. High pseudo‐total metal concentrations were also found in gravel bed sediments, probably associated with iron (Fe) and manganese (Mn) oxyhydroxides and discrete anthropogenic metal‐rich particles. These results highlight the importance of understanding the potential effects of urban river restoration upon sediment availability and channel hydraulics and consequent impacts upon sediment contaminant dynamics and storage. Copyright © 2014 John Wiley & Sons, Ltd.     

Resel filtering to aid visualisation within an exploratory data analysis system

Received: 18 July 1999 / Accepted: 30 December 1999     

Seasonal and diurnal variability of pressure fluctuation in the infrasound frequency range observed in the Czech microbarograph network

Infrasound environments in the Czech microbarograph network were studied. Reference Fourier amplitude spectra were calculated from data measured at three microbarograph sites of the network in May 2011-April 2012; directional analysis of infrasound arrivals in the frequency band 0.15-0.4 Hz was performed for the microbarograph array at Panská Ves in May 2014-April 2015. Diurnal, seasonal and site-to-site variability of the reference spectra was evaluated. Site-to-site variability is influenced by the location of the respective sensors in the open air and inside the observatory buildings and by local noise phenomena like wind turbines. Diurnal variability is well developed in summer with maximum ambient noise levels during the daytime and minima at night. Seasonal variability is observed at night with maxima in winter and minima in summer. Wind and wind eddies seem to be an important source of ambient noise in measurements in the Czech microbarograph network. A distinct spectral peak occurs near 0.2 Hz with amplitudes by about one order of magnitude higher in winter than in summer. Its seasonal variability is related to seasonal propagation of microbaroms from the source region in the Northern Atlantic.