Empirical predictors of annual bed load travel distance,and implications for salmonid habitat restoration and protection

Measurements of annual travel distance (L_b) of bed load sediment at 16 locations in Alaska, the intermountain USA, west coast USA and Scotland are strongly correlated with bankfull channel width (r² = 0·86, p < 0·001). Travel distance of particles is probably limited by trapping in bars, which have a longitudinal spacing proportional to channel width. Increased abundance of woody debris reduces bar spacing and may reduce L_b. Longer cumulative duration of bed load transporting flows in a year appears to increase L_b. Other predictors of annual travel distance such as stream power per unit length, drainage area and bankfull discharge were less well correlated with L_b (r² ranging from 0·27 to 0·51). Stream power per unit bed area, basal shear stress and slope were not significantly related to L_b (r² < 0·05). Most correlations were improved when regressions were limited to data from the west coast USA. Travel distance estimates can be used to help identify reaches that may take longer to recover from large, short‐term increases in sediment supply. Published in 2001 by John Wiley & Sons, Ltd.     

Diffusion effects on oxygen isotope temperatures of slowly cooled igneous and metamorphic rocks

Recently obtained data on oxygen diffusion in feldspars, quartz, and hornblende permit the prediction of the apparent¹⁸O¹⁶O temperatures that would be measured in a rock that consisted only of those three minerals, and cooled slowly from high temperature. The computed temperatures would be based on the differences in the¹⁸O¹⁶O ratios between coexisting pairs of minerals. The present calculation takes into account the diffusion rates for oxygen as a function of temperature, the cooling rate of the rock, the mineral grain sizes, and the mode of the rock. For mineral grains 1 mm in radius, and a cooling rate of 10°C/m.y., the minimum difference in apparent temperature between quartz-feldspar and feldspar-hornblende pairs will be 115°C, despite the assumption of a normal, uneventful, slow cooling history to room temperature. Further, the apparent quartz-hornblende temperature will range over 30°C (590–620°C) depending on the mode of the rock. For a cooling rate of 1000°C/m.y., the apparent difference in temperature can be as much as 400°C. Consequently, consistency in temperatures obtained by oxygen isotope analysis should not be expected in most high-grade metamorphic rocks or igneous rocks which are cooled slowly. Departures from the pattern of temperatures obtained in this model would imply a very rapid quench from high temperature, or a complex history for the rock. For some minerals, including hornblende, the relation between temperature and the equilibrium fractionation of oxygen isotopes between coexisting phases has been derived from observed relations in natural specimens. The choice of the specimens used for such calibrations needs to be re-evaluated in light of these findings. This may result in a change in the equilibrium equation constants.An example from the literature, the San Jose tonalite, Baja California, Mexico, was modelled and yieldsδ¹⁸O concentrations in the minerals that correspond closely with the measured values. This suggests that the model used is appropriate, that the rock has had a simple thermal history, and that it cooled at 100–200°C/m.y. over the temperature range 800–500°C. The set of paleotemperatures obtained for a rock will, in general, yield neither the mineral closure temperatures nor the formation or crystallization temperatures. On the other hand, the cooling rate of the rock may be derived from the data. This, in turn, may have important tectonic implications with regard to denudation and uplift rates.     

Geomagnetic control of polar mesosphere summer echoes

Using observations with the ALOMAR SOUSY radar near Andenes (69.3°N, 16.0°E) from 1994 until 1997 polar mesosphere summer echoes (PMSE) have been investigated in dependence on geomagnetic K indices derived at the Auroral Observatory Tromsø (69.66°N, 18.94°E). During night-time and morning hours a significant correlation between the signal-to-noise ratio (SNR) of the radar results and the geomagnetic K indices could be detected with a maximum correlation near midnight. The correlation becomes markedly smaller in the afternoon and early evening hours with a minimum near 17 UT. This diurnal variation is in reasonable agreement with riometer absorption at Ivalo (68.55°N, 27.28°E) and can be explained by the diurnal variation of ionization due to precipitating high energetic particles. Therefore, a part of the diurnal PMSE variation is caused by this particle precipitation. The variability of the solar EUV variation, however, has no significant influence on the PMSE during the observation period.     

Nature of the crust in Maine,USA: evidence from the Sebago batholith

 Neodymium and lead isotope and elemental data are presented for the Sebago batholith (293±2 Ma), the largest exposed granite in New England. The batholith is lithologically homogeneous, yet internally heterogeneous with respect to rare earth elements (REE) and Nd isotopic composition. Two-mica granites in the southern/central portion of the batholith (group 1) are characterized by REE patterns with uniform shapes [Ce_N/Yb_N (chondrite normalized) = 9.4–19 and Eu/Eu* (Eu anomaly) = 0.27–0.42] and ɛ _Nd(t) = −3.1 to −2.1. Peripheral two-mica granites (group 2), spatially associated with stromatic and schlieric migmatites, have a wider range of total REE contents and patterns with variable shapes (Ce_N/Yb_N = 6.1–67, Eu/Eu* = 0.20–0.46) and ɛ _Nd(t) = −5.6 to −2.8. The heterogeneous REE character of the group 2 granites records the effects of magmatic differentiation that involved monazite. Coarse-grained leucogranites and aplites have kinked REE patterns and low total REE, but have Nd isotope systematics similar to group 2 granites with ɛ _Nd(t) = −5.5 to −4.7. Rare biotite granites have steep REE patterns (Ce_N/Yb_N = 51–61, Eu/Eu* = 0.32–0.84) and ɛ _Nd(t) = −4.6 to −3.8. The two-mica granites have a restricted range in initial Pb isotopic composition (²⁰⁶Pb/²⁰⁴Pb = 18.41–18.75; ²⁰⁷Pb/²⁰⁴Pb = 15.60–15.68; ²⁰⁸Pb/²⁰⁴Pb = 38.21–38.55), requiring and old, high U/Pb (but not Th/U) source component. The Nd isotope data are consistent with magma derivation from two sources: Avalon-like crust (ɛ _Nd>−3), and Central Maine Belt metasedimentary rocks (ɛ _Nd<−4), without material input from the mantle. The variations in isotope systematics and REE patterns are inconsistent with models of disequilibrium melting which involved monazite. Received: 8 December 1995 / Accepted: 29 April 1996     

Organic pollutants associated with macromolecular soil organic matter: Mode of binding

A study of ether-linked moieties in macromolecular bound residues of polycyclic aromatic hydrocarbons (PAH) generated in bioremediation experiments was performed using high temperature hydrolysis degradation with subsequent analysis of the products by GC-MS. This hydrolysis reaction was specifically designed to cleave ether bonds including relatively stable diarylether structures. Among the reaction products, aromatic alcohols representing typical microbiologically derived metabolites of PAH were found in addition to natural compounds. Thus, parts of the bound residues appeared to be linked within the macromolecular material by ether bonds. Model experiments with an oxidoreductase enzyme and aromatic alcohols indicate the formation of these ether bonds to be an enzyme-catalysed process.     

When hazard avoidance is not an option: lessons learned from monitoring the postdisaster Oso landslide,USA

On 22 March 2014, a massive, catastrophic landslide occurred near Oso, Washington, USA, sweeping more than 1 km across the adjacent valley flats and killing 43 people. For the following 5 weeks, hundreds of workers engaged in an exhaustive search, rescue, and recovery effort directly in the landslide runout path. These workers could not avoid the risks posed by additional large-scale slope collapses. In an effort to ensure worker safety, multiple agencies cooperated to swiftly deploy a monitoring and alerting system consisting of sensors, automated data processing and web-based display, along with defined communication protocols and clear calls to action for emergency management and search personnel. Guided by the principle that an accelerating landslide poses a greater threat than a steadily moving or stationary mass, the system was designed to detect ground motion and vibration using complementary monitoring techniques. Near real-time information was provided by continuous GPS, seismometers/geophones, and extensometers. This information was augmented by repeat-assessment techniques such as terrestrial and aerial laser scanning and time-lapse photography. Fortunately, no major additional landsliding occurred. However, we did detect small headscarp failures as well as slow movement of the remaining landslide mass with the monitoring system. This was an exceptional response situation and the lessons learned are applicable to other landslide disaster crises. They underscore the need for cogent landslide expertise and ready-to-deploy monitoring equipment, the value of using redundant monitoring techniques with distinct goals, the benefit of clearly defined communication protocols, and the importance of continued research into forecasting landslide behavior to allow timely warning.

     

GPR studies over the tsunami affected Karaikal beach,Tamil Nadu,south India

In this study, results of GPR profiling related to mapping of subsurface sedimentary layers at tsunami affected Karaikal beach are presented . A 400 MHz antenna was used for profiling along 262 m stretch of transect from beach to backshore areas with penetration of about 2.0 m depth (50 ns two-way travel time). The velocity analysis was carried out to estimate the depth information along the GPR profile. Based on the significant changes in the reflection amplitude, three different zones are marked and the upper zone is noticed with less moisture compared to other two (saturated) zones. The water table is noticed to vary from 0.5 to 0.75 m depth (12–15 ns) as moving away from the coastline. Buried erosional surface is observed at 1.5 m depth (40–42 ns), which represents the limit up to which the extreme event acted upon. In other words, it is the depth to which the tsunami sediments have been piled up to about 1.5 m thickness. Three field test pits were made along the transect and sedimentary sequences were recorded. The sand layers, especially, heavy mineral layers, recorded in the test pits indicate a positive correlation with the amplitude and velocity changes in the GPR profile. Such interpretation seems to be difficult in the middle zone due to its water saturation condition. But it is fairly clear in the lower zone located just below the erosional surface where the strata is comparatively more compact. The inferences from the GPR profile thus provide a lucid insight to the subsurface sediment sequences of the tsunami sediments in the Karaikal beach.     

A generalized geo-hazard warning system

An automated geo-hazard warning system is the need of the hour. It is integration of automation in hazard evaluation and warning communication. The primary objective of this paper is to explain a geo-hazard warning system based on Internet-resident concept and available cellular mobile infrastructure that makes use of geo-spatial data. The functionality of the system is modular in architecture having input, understanding, expert, output and warning modules. Thus, the system provides flexibility in integration between different types of hazard evaluation and communication systems leading to a generalized hazard warning system. The developed system has been validated for landslide hazard in Indian conditions. It has been realized through utilization of landslide causative factors, rainfall forecast from NASA??s TRMM (Tropical Rainfall Measuring Mission) and knowledge base of landslide hazard intensity map and invokes the warning as warranted. The system evaluated hazard commensurate with expert evaluation within 5?C6?% variability, and the warning message permeability has been found to be virtually instantaneous, with a maximum time lag recorded as 50?s, minimum of 10?s. So it could be concluded that a novel and stand-alone system for dynamic hazard warning has been developed and implemented. Such a handy system could be very useful in a densely populated country where people are unaware of the impending hazard.     

An assessment of three satellite-based precipitation data sets as applied to the Thailand region

The study examines three satellite-based data sets to estimate long-term precipitation for the Thailand region: the Tropical Rainfall Mapping Mission (TRMM) 3B43, the Climate Prediction Centre morphing technique (CMORPH), and a locally developed regression model using the geostationary meteorological satellite (GMS) covering the Thailand region. Data for the first two sets were available at a spatial resolution of 0.25° × 0.25°, while the local regression model used data from the GMS at a resolution of 5 km × 5 km. The statistical regression model was developed by relating long-term monthly average precipitation from 27 rain gauge stations with concurrent satellite data in the visible and thermal infrared bands. The model was then tested against independent data from 27 rain gauge stations. Satellite/rain gauge ratios were estimated, and a smooth spline surface was used to correct the error from the model. Data from the three approaches were compared with a rain gauge network. The TRMM relation performed better than CMORPH, and the performance for GMS was comparable to TRMM with root mean square different and mean bias difference of 33.6 and 4.2%, respectively. The locally developed regression model was used to produce monthly and yearly total rainfall maps from the GMS data for the entire country.     

Mantle Mush Compaction: a Key to Understand the Mechanisms of Concentration of Kimberlite Melts and Initiation of Swarms of Kimberlite Dykes

Kimberlite pipes or dykes tend to occur in clusters (a few kilometresin diameter) within fields 30–50 km in diameter. Theyare generally considered to originate from low degrees of partialmelting of carbonated peridotite within zones of ascending mantle.Numerical modelling shows that at the depth of formation ofkimberlite melts (>>200 km), mantle compaction processescan result in the formation of melt pockets a few tens of kilometresacross, with melt concentrations up to 7%. The initiation ofswarms of kimberlite dykes at the top of these melt pocketsis inevitable because of the large excess pressure between themelt and the surrounding solid, which exceeds the hydraulicfracturing limit of the overlying rocks. After their initiationat mantle depth the swarm of dykes may reach the surface ofthe Earth when the entire cratonic lithosphere column is inextension. We propose that kimberlite fields represent the surfaceenvelope of dyke swarms generated inside a melt pocket and thatkimberlite clusters represent the discharge of melt via dykesoriginating from sub-regions of the pocket. This model reproducesthe worldwide average diameter of kimberlite fields and is consistentwith the observation that some of the main kimberlite fieldsdisplay age ranges of c. 10 Myr. It is deduced that, at thescale of the Kaapvaal craton, different fields such as Kimberley,N. Lesotho and Orapa, dated at 80–90 Ma, probably resultfrom synchronous melt pockets forming inside an ascending mantleflow. The same model could apply to the fields of the Rietfontein,Central Cape and Gibeon districts dated at 60–70 Ma. Itis suggested that the same mantle flow that produced the Kimberley,N. Lesotho and Orapa fields migrated over 20–30 Myr afew hundred kilometres westward to form the Rietfontein, CentralCape and Gibeon fields. KEY WORDS: kimberlites; mantle; compaction; convection; volcanism