Observing total solar eclipses from near the edge of the predicted path

Suitable observations from various locations in the predicted path of a total solar eclipse can provide information about the relative positions and shapes of the Sun and Moon to about ±0.02. The total solar eclipse of 1972, July 10 was observed from locations near the edges of its predicted path. The durations of the limb phenomena were greatly enhanced. Preliminary analysis of the observations shows that the eclipse shadow passed 3 km northeast of its predicted path.Communication presented at the conference on Lunar Dynamics and Observational Coordinate Systems held January 15–17, 1973 at the Lunar Science Institute, Houston, Tex., U.S.A.     

Evolution of basin architecture in an incipient continental rift: the Cenozoic Most Basin, Eger Graben (Central Europe)

The Oligo-Miocene Most Basin is the largest preserved sedimentary basin within the Eger Graben, the easternmost part of the European Cenozoic Rift System (ECRIS). The basin is interpreted as a part of an incipient rift system that underwent two distinct phases of extension. The first phase, characterised by NNE–SSW- to N–S-oriented horizontal extension between the end of Eocene and early Miocene, was oblique to the rift axis and caused evolution of a fault system characterised by en-échelon-arranged E–W (ENE–WSW) faults. These faults defined a number of small, shallow initial depocentres of very small subsidence rates that gradually merged during the growth and linkage of the normal fault segments. The youngest part of the basin fill indicates accelerated subsidence caused probably by the concentration of displacement at several major bounding faults. Major post-depositional faulting and forced folding were related to a change in the extension vector to an orthogonal position with respect to the rift axis and overprinting of the E–W faults by an NE–SW normal fault system. The origin of the palaeostress field of the earlier, oblique, extensional phase remains controversial and can be attributed either to the effects of the Alpine lithospheric root or (perhaps more likely because of the dominant volcanism at the onset of Eger Graben formation) to doming due to thermal perturbation of the lithosphere. The later, orthogonal, extensional phase is explained by stretching along the crest of a growing regional-scale anticlinal feature, which supports the recent hypothesis of lithospheric folding in the Alpine–Carpathian foreland.     

The Use of LiDAR in Digital Surface Modelling: Issues and Errors

Modelling and extracting 3D geographical data presents numerous challenges that require continual research to attempt to evolve an efficient, reliable and accurate solution. LiDAR data capture and analysis has become a preferred acquisition choice for elevation data because the resulting quality and level of detail far exceeds traditional methods for large survey areas. As with any data collection system, LiDAR is prone to errors. Analysing these errors, ascertaining causes and producing error correction strategies is vital if accurate and confident results are to be obtained. Eight years of LiDAR datasets (from 1998 to 2005) have been closely analysed for a large coastal area of South Wales. This article provides a detailed and accurate summary of the identified LiDAR data issues and subsequent errors which affect the accuracy of end products such as Digital Surface Models (DSMs).     

Quantitative taxonomy and biostratigraphy of Middle Cambrian trilobites from Montana and Wyoming

This study was made to revise the taxonomy and biostratigraphy of Middle Cambrian trilobites from Montana and Wyoming. Both numerical and conventional analyses were made of the taxonomic and biostratigraphic data. Numerical taxonomy was performed on a sample of 210 OTU's (Operational Taxonomic Units) using 66 characters which were determined on cranidia of Middle Cambrian ptychopariid trilobites. These characters consisted of linear measurements which were transformed to indices proportional to glabellar length, quantitative-qualitative shape or angle measurements, and multistate attributes. The similarity coefficients calculated were average taxonomic distances and Pearson's product-moment correlation coefficient. The matrices of similarity coefficients were clustered by single-linkage and unweighted pair-group algorithms. The coordinates of OTU's in a three-dimensional A-space defined by the first three principal axes also were calculated. A phenogram of the distance matrix clustered by UPGMA (which yielded the highest cophenetic correlation coefficient) and a three-dimensional pin-and-ball model were used to interpret the trilobite taxonomy. Insufficiently clear clustering in both representations of taxonomic structure necessitated also a conventional taxonomic study guided by the numerical phenetics. Numerical biostratigraphy was performed with 79 collections as OTU's and 43 trilobite genera as characters. Jaccard coefficients were used as similarity coefficients, and the results were clustered by UPGMA. The resultant phenogram was readily interpretable, and seven faunal assemblage zones (Albertella, Glossopleura, Ehmaniella, Bolaspis-Glyphaspis, Ehmania, Parehmania, and Bolaspidella)are defined for the Middle Cambrian in the study area. Two of the zones (Ehmaniellaand Parehmania)are new and replace part of the previously defined “Bathyuriscus-Elrathina”zone. Bolaspis-Glyphaspis, Ehmania,and Parehmaniazones may have only regional validity.     

Late Pleistocene and Early Holocene lake‐level fluctuations in the Lahontan Basin,Nevada: Implications for the distribution of archaeological sites

The Great Basin of the western U.S. contains a rich record of Late Pleistocene and Holocene lake‐level fluctuations as well as an extensive record of human occupation during the same time frame. We compare spatial‐temporal relationships between these records in the Lahontan basin to consider whether lake‐level fluctuations across the Pleistocene‐Holocene transition controlled distribution of archaeological sites. We use the reasonably well‐dated archaeological record from caves and rockshelters as well as results from new pedestrian surveys to investigate this problem. Although lake levels probably reached maximum elevations of about 1230–1235 m in the different subbasins of Lahontan during the Younger Dryas (YD) period, the duration that the lakes occupied the highest levels was brief. Paleoindian and Early Archaic archaeological sites are concentrated on somewhat lower and slightly younger shorelines (_1220–1225 m) that also date from the Younger Dryas period. This study suggests that Paleoindians often concentrated their activities adjacent to large lakes and wetland resources soon after they first entered the Great Basin. © 2008 Wiley Periodicals, Inc.     

Wind erosion of the wind-deposited Navajo Sandstone, USA

Outcrops of the Early Jurassic Navajo Sandstone in southern Utah and northern Arizona, south-western USA are being actively eroded by sand-laden, south-westerly winds. Small-scale stepped topography with risers facing into the wind develops even on steep canyon walls when wind-swept grains strike the rock at a low angle. Photosynthetic, endolithic microbes directly underlie most outcrop surfaces; the crusts formed by these organisms are essential to formation of the small-scale steps. Wind erosion of highlands also forms troughs and pits that are tens of metres across. The pits have deeply scalloped, overhanging walls, and contain central domes surrounded by 'moats' filled with dune sand. Wind erosion of aeolian sandstone is favoured by a positive feedback mechanism in which grains that are liberated from outcrops by impacting particles become a fresh supply of pre-sorted abrasive particles for further attack.     

Comparative Analysis of a Transition Region Bright Point with a Blinker and Coronal Bright Point Using Multiple EIS Emission Lines

Since their discovery 20 year ago, transition region bright points have never been observed spectroscopically. Bright point properties have not been compared with similar transition region and coronal structures. In this work we have investigated three transient quiet Sun brightenings including a transition region bright point (TR BP), a coronal bright point (CBP) and a blinker. We use time-series observations of the extreme-ultraviolet emission lines of a wide range of temperature T (logT=5.3?–?6.4) from the EUV Imaging Spectrometer (EIS) onboard the Hinode satellite. We present the EIS temperature maps and Doppler maps, which are compared with magnetograms from the Michelson Doppler Imager (MDI) onboard the SOHO satellite. Doppler velocities of the TR BP and blinker are ≤?25 km?s^?1, which is typical of transient TR phenomena. The Doppler velocities of the CBP were found to be ≤?20 km?s^?1 with exception of those measured at logT=6.2 where a distinct bi-directional jet is observed. From an EM loci analysis we find evidence of single and double isothermal components in the TR BP and CBP, respectively. TR BP and CBP loci curves are characterized by broad distributions suggesting the existence of unresolved structure. By comparing and contrasting the physical characteristics of the events we find that the BP phenomena are an indication of multi-scaled self-similarity, given the similarities in both their underlying magnetic field configuration and evolution in relation to EUV flux changes. In contrast, the blinker phenomena and the TR BP are sufficiently dissimilar in their observed properties as to constitute different event classes. Our work is an indication that the measurement of similar characteristics across multiple event types holds class-predictive power, and is a significant step towards automated solar atmospheric multi-class classification of unresolved transient EUV sources. Finally, the analysis performed here establishes a connection between solar quiet region CBPs and jets.     

Using Strong Solar Coronal Emission Lines as Coronal Flux Proxies

We investigate the possibility that strong EUV lines observed with the Goddard Solar EUV Rocket Telescope and Spectrograph (SERTS) provide good proxies for estimating the total coronal flux over shorter wavelength ranges. We use coordinated SERTS and Yohkoh observations to obtain both polynomial and power-law fits relating the broad-band soft X-ray fluxes to the intensities of Fexvi 335 Ú and 361 Ú, Fexv 284 Ú and 417 Ú, and Mgix 368 Ú measured with SERTS. We found that the power-law fits best cover the full range of solar conditions from quiet Sun through active region, though not surprisingly the cooler Mgix 368 Ú line proves to be a poor proxy. The quadratic polynomial fits yield fair agreement over a large range for all but the Mgix line. However, the linear fits fail conspicuously when extrapolated into the quiet-Sun regime. The implications of this work for the Heii 304 Ú line formation problem are also briefly considered.