Major Ridge Research Articles

Modern changes of tidal troughs among the radial sand ridges in northern Jiangsu coastal zone

Using satellite images taken on different dates, GIS analysis of aerial photos, bathymetric maps and other field survey data, tidal troughs and major sand ridges in the northern Jiangsu coastal area were contrasted. The results show that there have been three types of movement or migration of tidal trough in this area: (1) Periodic and restricted, this type of trough usually developed along the beaches with immobile gully head as a result of the artificial dams and the swing range increased from gully head to the low reaches, so they have been obviously impacted by human activity and have longer swing periods; (2) Periodic and actively, this kind of trough, which swung with a fast rate and moved periodically on sand ridges, were mainly controlled by the swings of the host tidal troughs and hydrodynamic forces upon tidal sand ridge and influenced slightly by human constructions; (3) Steadily and slowly, they are the main tidal troughs with large scale and a steady orientation in this area and have slow lateral movement. The differences in migration mode of tidal trough shift result in different rates of migration and impact upon tidal sand ridges. Lateral accumulation on current tidal trough and deposition on abandoned tidal troughs are the two types of sedimentation of the tidal sand ridges formation. The whole radial sand ridge was generally prone to division and retreat although sand ridges fluctuated by the analysis of changes in talwegs of tidal troughs and shorelines of sand ridges.

Biochronology and paleoceanography of late Pleistocene and Holocene calcareous nannofossil abundances across the Arctic Basin

Late Pleistocene and Holocene stratigraphic distributions of calcareous nannofossils have been investigated in seven short cores raised from four major ridges in the Arctic Basin and in one core from the Norwegian Sea. Observed assemblages in the Arctic Ocean cores mostly represent the influence of Atlantic shallow waters. On the Gakkel and Lomonosov Ridges, a distinct cross-over in abundance occurs between Emiliania huxleyi and Gephyrocapsa spp. in the upper part of Marine Isotope Stage (MIS) 3. The lowest abundances of indigenous calcareous nannofossils occur in the southern Mendeleev Ridge core and in the two Alpha Ridge cores. These areas show a minor production of calcareous nannoplankton, probably because of the progressively diminishing influence of shallow Atlantic waters with the increasing distance from the Fram Strait gateway, the key conduit of shallow water inflow to the Arctic Ocean. It remains unknown whether or not the observed abundance patterns have been modified by glacial–interglacial scale changes in preservation. Obvious reworking becomes intensified around MIS boundaries.

Magnetic zoning and seismic structure of the South China Sea ocean basin

We made a systematic investigation on major structures and tectonic units in the South China Sea basin based on a large magnetic and seismic data set. For enhanced magnetic data interpretation, we carried out various data reduction procedures, including upward continuation, reduction to the pole, 3D analytic signal and power spectrum analyses, and magnetic depth estimation. Magnetic data suggest that the South China Sea basin can be divided into five magnetic zones, each with a unique magnetic pattern. Zone A corresponds roughly to the area between Taiwan Island and a relict transform fault, zone B is roughly a circular feature between the relict transform fault and the northwest sub-basin, and zones C, D, and E are the northwest sub-basin, the east sub-basin, and the southwest sub-basin, respectively. This complexity in basement magnetization suggests that the South China Sea evolved from multiple stages of opening under different tectonic settings. Magnetic reduction also fosters improved interpretation on continental margin structures, such as Mesozoic and Cenozoic sedimentary basins and the offshore south China magnetic anomaly. We also present, for the first time, interpretations of three new 2D reflection seismic traverses, which are of ~2,000 km in total length and across all five magnetic zones. Integration of magnetic and seismic data enables us to gain a better 3D mapping on the basin structures. It is shown that the transition from the southwest sub-basin to the east sub-basin is characterized by a major ridge formed probably along a pre-existing fracture zone, and by a group of primarily west-dipping faults forming an exact magnetic boundary between zones D and E. The northwest sub-basin has the deepest basement among the three main sub-basins (i.e., the northwest sub-basin, the southwest sub-basin, and the east sub-basin). Our seismic data also reveal a strongly faulted continent–ocean transition zone of about 100 km wide, which may become wider and dominated with magmatism or transit to an oceanic crust further to the northeast.

The climatology of small‐scale orographic precipitation over the Olympic Mountains: Patterns and processes

AbstractThe climatology of small‐scale patterns of mountain precipitation is poorly constrained, yet important for applications ranging from natural hazard assessment to understanding the geologic evolution of mountain ranges. Synthesizing four rainy seasons of high‐resolution precipitation observations and mesoscale model output (from the Penn State/NCAR MM5), reveals a persistent small‐scale pattern of precipitation over the ∼10 km wide, ∼800 m high ridges and valleys of the western Olympic Mountains, Washington State, USA. This pattern is characterized by a 50–70% excess accumulation over the ridge crests relative to the adjacent valleys in the annual mean. While the model shows excellent skill in simulating these patterns at seasonal time‐scales, major errors exist for individual storms.Investigation of a range of storm events has revealed the following mechanism for the climatological pattern. Regions of enhanced condensation of cloud water are produced by ascent in stable flow over the windward slopes of major ridges. Synoptically generated precipitation grows by collection within these clouds, leading to enhanced precipitation which is advected by the prevailing winds.Instances of atypical patterns of precipitation suggest that under certain conditions (during periods with a low freezing level, or convective cells) fundamental changes in small‐scale patterns may occur. However, case‐studies and composite analysis suggest that departures from the pattern of ridge‐top enhancement are rare; the basic patterns and processes appear robust to changes in temperature, winds, and background rainfall rates. Copyright © 2008 Royal Meteorological Society

<i>The Cherokee Nation: A History</i> (review)

Reviewed by: The Cherokee Nation: A History Gary C. Cheek Jr. Robert J. Conley . The Cherokee Nation: A History. Albuquerque: University of New Mexico Press, 2005. 265 pp. Cloth, $24.95. Robert Conley narrates the history of the Southeastern Cherokee, one of the largest and most renowned Indian cultures of the southeastern United States and Oklahoma. Although the author presents the stories of his tribe through narrative, he includes pertinent themes relative to the tribe's history in retrospect. Particularly, the book explores survival through cultural change, adaptation, and persistence in the face of difficult choices, forced removal, and attempts at detribalization. Conley places the reader in the shoes of the Cherokee and leads him or her on the path of the past from mythical origins to the development of economic and political progress and "nationalism." Cherokee Nation contains thirty-one concise, detailed chapters. The author superbly expatiates on important issues while including intriguing cultural examples, which include explanations about kinship and oral traditions to the significance of cultural preservation and lessons for the future noted by the twenty-first century. Historians who enjoy informative, emotionally driven works will certainly enjoy such chapters as "Hundreds of Babies Died," concerning Cherokee removal and experiences within "concentration camps," and "The First Woman Chief," which explores the provocative character and historical impact of Wilma Mankiller, who became principal chief of the Cherokee in 1987. Perhaps athe best part of the book concerns subjects about Cherokee often not discussed in survey literature. Conley does an excellent job of discussing intertribal political tensions in chapter 30, entitled "What Do They Want with This Old Building?" Moreover, for this reviewer, chapter 26, simply called "World War II," describes the Cherokee struggles on the home front and the meritorious service of those men who fought in the conflict. After the war some American Indians benefited and attended college with funds from the GI Bill. Cherokee gender roles changed as women entered the workforce as their American, non-Indian counterparts. One of the strongest aspects of this book involves Conley's strategic use of [End Page 536] photographs, original documents, suggestive reading lists, and glossaries. Each chapter recommends materials that further elaborate on the subject explored by individual sections. Detailed glossaries aid in understanding Cherokee terminology, political rhetoric, and organizational names. Original documents both within chapters and included in appendixes prompt the reader to make his or her own judgments in light of Conley's topical overviews. Researchers often forget that history is as much seeing as reading. The included photographs portray several well-known figures, including John Ross, Major Ridge, Sequoyah, and Wilma Mankiller. Maps and pictures of buildings depict proud achievements, horrific poverty, and massive Cherokee landholdings during various periods of their history. Conley's work provides an informative guide to the Cherokee, a story that he weaves into the fabric of southeastern Native America, U.S. policy, and culture revision. Moreover, its scope and breadth surely entertain as much as they inform. Gary C. Cheek Jr. Mississippi State University Copyright © 2008 University of Nebraska Press

Macrolichens as Biomonitors of Air-quality Change in Western Pennsylvania

Species richness of corticolous macrolichens was monitored at one- or two-year intervals on a total of 63 plots from 1997–2003 in a region of west-central Pennsylvania that included four coal-fired power generating stations and an industrial city. Lichen richness significantly increased from an average of 5.7 species/plot in 1997 to 9.3 species/plot in 2003. A linear mean rate of gain in species on regional monitoring plots was 0.56 species/yr. Plots along a major ridge top had a slower but significant gain in richness, and a localized area flanked by the city and two generating stations exhibited less lichen recolonization. Our results confirm the value of macrolichens as indicators of air quality and the importance of examining temporal as well as spatial changes in lichen richness to ascertain air-quality status.

Precipitation over multiscale terrain

Stratiform precipitation over multiscale terrain is examined based on two-dimensional simulations of moist airflow past two-ridge terrain with a narrower ridge superposed on the windward slope of a wider ridge. It has been demonstrated that the narrower ridge could significantly modulate the precipitation intensity and distribution by inducing upslope ascent, leeside descent, and gravity waves.Three distinct flow regimes have been identified based on simulations, namely linear, non-linear, and blocking regimes. For low terrain, the wave response is primarily linear, and more precipitation occurs over the narrower ridge. Precipitation over the major ridge is much reduced by precipitation over the narrower ridge, which decreases the moisture flux that reaches the major ridge, and by leeside descent over the narrower ridge, which limits the horizontal dimension of the updraft zone over the major ridge. In the linear regime, the total precipitation produced by the two-ridge terrain and the corresponding wide smooth ridge is comparable. For terrain of moderate heights, the wave response is nonlinear and oscillation occurs with updraft and precipitation maxima alternating between the upwind slopes of the two ridges, likely due to non-linear wave—wave interaction. Strong lee waves are produced in the lee of the first ridge due to non-linear amplification and could significantly enhance precipitation over the major ridge through directly increasing the condensation rate over the upwind slope of the major ridge and through generating snow above the freezing level. Correspondingly, precipitation rates over the two ridges become comparable and the total precipitation over the tworidge terrain is considerably larger than over the corresponding reference ridge. For higher terrain, blocking becomes significant and precipitation over the first ridge tends to detach from the terrain and propagates upstream.Additional simulations indicate that the precipitation intensity and distribution are also sensitive to terrain geometry such as the ratio of the two ridge heights, the depth of the relative valley, and the distance between the two ridges.

A three-dimensional radially anisotropic model of shear velocity in the whole mantle

SUMMARY We present a 3-D radially anisotropic S velocity model of the whole mantle (SAW642AN), obtained using a large three component surface and body waveform data set and an iterative inversion for structure and source parameters based on Non-linear Asymptotic Coupling Theory (NACT). The model is parametrized in level 4 spherical splines, which have a spacing of ! 8 . The model shows a link between mantle flow and anisotropy in a variety of depth ranges. In the uppermost mantle, we confirm observations of regions with VSH > VSV starting at ! 80 km under oceanic regions and ! 200 km under stable continental lithosphere, suggesting horizontal flow beneath the lithosphere. We also observe a VSV > VSH signature at ! 150‐300 km depth beneath major ridge systems with amplitude correlated with spreading rate for fast-spreading segments. In the transition zone (400‐700 km depth), regions of subducted slab material are associated with VSV > VSH, while the ridge signal decreases. Whilethemid-mantlehasloweramplitudeanisotropy( VSV in the lowermost 300 km, which appears to be a robust conclusion, despite an error in our previous paper which has been corrected here. The 3-D deviations from this signature are associated with the large-scale low-velocity superplumes underthecentralPacificandAfrica,suggestingthatVSH >VSV isgeneratedinthepredominant horizontal flow of a mechanical boundary layer, with a change in signature related to transition to upwelling at the superplumes.

A meso-scale three-dimensional dynamical model of orographic rainfall

A mesoscale three-dimensional (3-D) dynamical model is presented to diagnose orographic rainfall, with particular reference to the Western Ghats (WG) in India. This model has two parts, namely, a dynamical part and a thermodynamical part. In the dynamical part the vertical velocity induced by a mesoscale elliptical orographic barrier has been computed using the perturbation technique. In the thermodynamical part rainfall intensity (RFI) has been computed using the computed vertical velocities, with the help of continuity of moisture and mass. The computed RFI has been compared with observed RFI as well as with that computed by 2-D model. The present study shows that during the southwest monsoon season (SWMS), orographic rainfall enhancement in the WG area appears to be solely due to the vertical shear of the basic flow and its variation with height. Stability appears to have very little influence on it. The spatial distribution of RFI across the barrier shows that there are four regions of maximum rainfall, one primary on the windward side behind the peak of the barrier and three secondary on the leeward side. The symmetry in the locations of these secondary rainfall maxima appears to be critically dependent on the component of basic flow parallel to the major ridge axis of the barrier.

Carapace formation of the podocopid ostracode Semicytherura species (Crustacea: Ostracoda)

Details of ostracode carapace structures were examined by SEM and TEM. The podocopine ostracode Semicytherura kazahana has major ridges on the carapace surface and develops its prismatic layer inside the adult carapace. Electron microscopy at the final molt reveals that the major ridges arise from the highly dense formation of pits within the underlying swollen epidermis, and that disappearance of the epidermis in the presumptive area of the prismatic layer occurs after the calcification of the outer lamella cuticle, and just before synthesis of the membranous layer. These facts suggest that the formation of the carapace in Semicytherura takes place via a more complex process than that of the other podocopid ostracodes.

Print, Cultural Memory, and John Rollin Ridge's The Life and Adventures of Joaquín Murieta, the Celebrated California Bandit

LORI MERISH Print, Cultural Memory, and John Rollin Ridge's The Life and Adventures ofJoaquin Murieta, the Celebrated California Bandit The postindian warriors hover at last over the ruins of tribal representations and surmount the scriptures of manifest manners with new stories; these warriors counter the sutveillance and literature of dominance with their own simulations of survivance. The postindian arises from the earlier inventions of the tribes only to contravene the absence of the real with theatrical performances; the theater of tribal consciousness is the recreation of the real, not the absence of the real in the simulations of dominance. Gerald Vizenor, Manifest Manners I want to write the history of the Cherokee Nation as it Should be written and not as white men will wtite it and as they will tell the tale, to screen and justify themselves. All this I can nevet do unless I get into the proper position to wield influence and make money. . . . Instead of writing for my living [in California] I should be using my pen in behalf of my own people and in rescuing from oblivion the proud names of our race. ... If there ever was a man on earth that loved his people and his kindred, I am that man. John Rollin Ridge, letter to Stand Watie, October 9, 1854 As far back as I can remember, I belonged to a secret society of Indian women, meeting around a kitchen table in a conspiracy to bring the past into the present. I listened, their stories settling forever in my blood, and I knew the stories were told and told not for carrying but for keeping. They heard, and they taught me to heat, the truth in things not said. They listened, and they taught me to listen, in the space between words. Betty Louise Bell (Cherokee), Faces in tL· Moon Arizona Quarterly Volume 59, Number 4, Winter 2003 Copyright © 2003 by Arizona Board of Regents ISSN 0004-1610 32Lori Merish The Life and Adventures ofJoaquin Murieta, the Celebrated California Bandit, an 1854 novel by mixedblood Cherokee author John Rollin Ridge (or Yellow Bird, the English translation of his Cherokee name Cheesquatalawny) was the first published novel by a Native American. Ridge was a journalist, poet, and novelist who was born in Georgia in 1827, only a few years before the Cherokee were forced to emigrate to Indian Territory in Oklahoma—an event of tremendous import in his life, and for his work. His was one of the most powerful families in the Cherokee Nation: his grandfather, Major Ridge, was a noted tribal leader, as were his father, John Ridge, and his uncles, Elias Boudinot (Buck Watie) and Stand Watie, and they were centrally involved in the divisive political history of the Cherokee Nation during the 1820s and 30s. In particular, his father, trained as a lawyer, and Boudinot, editor of the Cherokee Phoenix, were early leaders in the fight against Removal ; in 1835, aftet President Jackson refused to enforce the Supreme Court decision to uphold Cherokee property and civil rights against illegal encroachment by the state of Georgia and Removal seemed to them inevitable, Ridge and Boudinot drew up the treaty whereby Removal was negotiated. The "Treaty Party's" actions alienated the family from most Cherokees, including followers of the powerful chief John Ross, and led to the execution of Rollin Ridge's grandfather, uncle, and father by members of the Ross faction several years later. (When John Ridge signed the Treaty of New Echota, he reportedly announced, "I have signed my death warrant."1) These events informed, perhaps motivated Ridge's account of the violence that ensued from Anglo landgrabbing and manifest destiny in Joaquin. Focusing on the newly annexed, contested terrain of California, Ridge counters Euroamerican narratives of "discovery" and the Edenic representations of Western "virgin land" (such as those found in John Fiémont's writing), making space for what José David Saldivai terms "an alternative narrative of what can now be called the ethno-iacialized cultures of displacement" (7). In doing so, Ridge, like many other early Native American writers, appropriated the forms, rhetorics, and conventions of Euroamerican print culture, utilizing them as what Michel de Certeau terms...

La Moraine du Lac Bluenose (Territoires du Nord-Ouest), une moraine à noyau de glace de glacier

Au sud du détroit du Dolphin et de l'Union, dans les Territoires du Nord-Ouest, des crêtes morainiques hautes de 100 m, composées de till à gros blocs marquent l'emplacement d'un front glaciaire à l'est et au nord du lac Bluenose. Les principales crêtes sont soit massives, soit composites avec de petites crêtes secondaires à leur sommet. En amont glaciaire (est) des crêtes, les formes de relief les plus fréquentes sont des collines recouvertes de blocs dont la hauteur atteint 60 m et des monticules entre lesquels se trouvent de nombreux lacs. Un important glissement de terrain au cœur de la moraine expose de la glace riche en sédiments, enfouie sous 3 m de till. Ce diamicton à matrice sabloneuse et riche en blocs exhibe une structure en colonnes et une fissilité prismatique. La glace enfouie qui incorpore des blocs et des cailloux est zonée, ce qui permet de déceler des plis et des déformations plus complexes. Le contact entre la glace enfouie et le diamicton est net, sub-horizontal et discordant. La glace est interprétée comme étant la partie basale d'un glacier enfouie par des sédiments glacigéniques, surtout du till. Dans une zone à écoulement à contre pente de la partie frontale de l'inlandsis du Wisconsinen supérieur des chevauchements ont transporté des sédiments qui ont recouvert la glace morte à la marge du front de glace active. Nous croyons que dans l'éventualité où un réchauffement climatique causerait la fonte de la glace enfouie, laquelle représente un volume important de la Moraine du Lac Bluenose, le relief serait transformé en un paysage bosselé semblable à celui qui existe dans des régions plus méridionales du Canada central.

Trichostome ciliates from Australian marsupials. I. Bandia gen. nov. (Litostomatea: Amylovoracidae)

A new genus of amylovoracid ciliates, Bandia gen.nov., is described. They are endosymbiotic/endocommensal in the stomachs of macropodid marsupials. Six new species, B. beveridgei, B. equimontanensis, B. tammar, B. deveneyi, B. cribbi and B. smalesae, are described from Setonix brachyurus, Petrogale assimilis, Macropus eugenii, M. robustus, M. parryi and M. agilis respectively. The gross morphology of Bandia is similar to that of Bitricha, with holotrichous somatic ciliation in two fields, longitudinal dorsal and oblique ventral. The somatic kineties are arranged in groups between non-ciliated. major interkinetal ridges; the groups of kineties thus give the cell a banded appearance. Several species are bimorphic, one form holotrichous and the other with a glabrous right body groove which appears to be derived from an ingrowth of one of the major interkinetal ridges. The groove may function in attachment either in sequestration or conjugation. The ultrastructure of the somatic kineties and the oral structures is similar to that of Amylovorax. Bandia also has unique ultrastructural features associated with the major interkinetal ridges, right body groove and a karyophore. Morphological evolution within the Amylovoracidae may have proceeded from simple forms such as Amylovorax via a process of cellular torsion and/or oral migration to forms similar to Bitricha and by further torsion and cellular elaboration to Bandia.

Revised tectonic boundaries in the Cocos Plate off Costa Rica: Implications for the segmentation of the convergent margin and for plate tectonic models

The oceanic Cocos Plate subducting beneath Costa Rica has a complex plate tectonic history resulting in segmentation. New lines of magnetic data clearly define tectonic boundaries which separate lithosphere formed at the East Pacific Rise from lithosphere formed at the Cocos‐Nazca spreading center. They also define two early phase Cocos‐Nazca spreading regimes and a major propagator. In addition to these sharply defined tectonic boundaries are overprinted boundaries from volcanism during passage of Cocos Plate over the Galapagos hot spot. The subducted segment boundaries correspond with distinct changes in upper plate tectonic structure and features of the subducted slab. Newly identified seafloor‐spreading anomalies show oceanic lithosphere formed during initial breakup of the Farallon Plate at 22.7 Ma and opening of the Cocos‐Nazca spreading center. A revised regional compilation of magnetic anomalies allows refinement of plate tectonic models for the early history of the Cocos‐Nazca spreading center. At 19.5 Ma a major ridge jump reshaped its geometry, and after ∼14.5 Ma multiple southward ridge jumps led to a highly asymmetric accretion of lithosphere. A suspected cause of ridge jumps is an interaction of the Cocos‐Nazca spreading center with the Galapagos hot spot.

Natural selection causing microsatellite divergence in wild emmer wheat at the ecologically variable microsite at Ammiad, Israel

Genetic diversity at 28 microsatellite loci was studied in a natural population of Triticum dicoccoides at the Ammiad microsite, north of the Sea of Galilee, Israel. This microsite was subdivided into four major habitats, North, Valley, Ridge and Karst, and further subdivided into nine subhabitats. The units thus defined showed strong and highly significant differentiation in ecological factors; in particular with respect to cover, proximity and height of rocks, and surface soil moisture after early rains. The results showed that allele distributions at microsatellite loci were nonrandom and associated with habitats. Significant genetic differentiation and variation in repeat number were found among subpopulations in the four major habitats and nine subhabitats. Habitat-specific and -unique alleles and linkage disequilibria were observed in the Karst subpopulation. The subpopulations dwelling in drier habitats and subhabitats showed higher genetic diversities at microsatellite loci. These results suggest that natural selection, presumably through aridity stress, acts upon microsatellite divergence predominantly on noncoding sequences, thereby contributing to differences in fitness.

Effects of natural habitat fragmentation on an endemic scrub lizard (Sceloporus woodi): an historical perspective based on a mitochondrial DNA gene genealogy.

The Florida scrub lizard, Sceloporus woodi, is endemic to scrub habitat patches along the central portion of the Florida peninsula and xeric coastal regions. Scrub ecosystems are the patchily distributed remnants of previously widespread habitats formed during the Pleiocene and early Pleistocene. Scrub lizards appear to have limited dispersal capabilities due to high habitat specificity and low mobility. To assess the population structure and phylogeography of S. woodi, 135 samples were collected from 16 patches on five major ridges in Florida, USA. Analysis of 273 bp of mitochondrial DNA (mtDNA) cytochrome b reveals a very strong geographic distribution of genetic diversity. Haplotype frequencies are significantly different in 63 of 66 comparisons between patches. With one exception, samples from the five major ridges are characterized by fixed differences in haplotype distribution and deep evolutionary separations (3-10%). Fixed genetic differences were also observed between northern and southern segments of several ridges. Analysis of molecular variance (AMOVA) shows an estimated 10.4% total genetic variation within patches, 17.5% among patches (within ridges), and 72.1% among ridges. This strong population structure among patches within ridges indicates that the distribution of S. woodi is tightly linked to sandy scrub habitat and that the discontinuous distribution of scrub habitats significantly inhibits dispersal and gene flow. Phylogeographic analyses indicate a pattern of dispersal down the Florida peninsula during the late Pliocene-early Pleistocene, followed by habitat fragmentation and variant isolation events. Therefore, the deep genetic structuring among scrub lizard populations on separate ridges is attributed to ancient isolation events induced by a shift from dry (xeric) to wet (mesic) conditions on the Florida peninsula. These findings indicate that some scrub lizard populations have persisted in isolation for time frames in excess of 1 Myr, providing a case history on the genetic consequences of habitat fragmentation.

Contrasting Vegetation of Noses and Hollows in the Valley and Ridge Province, Southwestern Virginia

STEPHENSON, S.L. (Department of Biology, Fairmont State College, Fairmont, WV 26554) AND H. H. MILLS (Department of Earth Sciences, Tennessee Technological University, Cookeville, TN 38505). Contrasting vegetation of nQses and hollows in the Valley and Ridge province, southwestern Virginia. J. Torrey Bot. Soc. 126: 197-212. 1999. The most prominent secondary landforms in the Valley and Ridge province are the small valleys and intervening ridges, commonly called hollows and noses, that corrugate the flanks of major ridges. Noses and hollows are relatively uniform both with respect to form and surficial materials on a given ridge flank. Knowledge of the distribution of vegetation associated with these landforms, therefore, is a key to the understanding of the overall pattern of vegetation in this province. We selected three study localities in southwestern Virginia that differed greatly in two or more of the following variables: bedrock, surficial deposits, elevation, and aspect. We described the vegetation in four hollows and on four noses at each of these three localities. Large differences between noses and hollows were found to exist in all three localities, differences that equal or exceed the differences between the study localities. For example, on a north-facing ridge flank with bouldery soils, Betula lenta had an importance value of 38.6 in hollows but only 0.6 on noses, whereas Quercus prinus displayed a value of 24.7 on noses but did not occur in hollows. On a south-facing ridge flank with bouldery soils, Quercus alba had an importance value of 37.4 on noses but was completely absent in hollows. On a northwest-facing ridge flank with steep-walled V-shaped hollows and thin shale-chip soil, Pinus pungens had an importance value of 31.2 on noses but did not occur in hollows. Compositional differences were even greater for shrubs and herbaceous plants. In addition, tree density, sapling density, shrub density, herb stratum cover, rock cover, and species richness differed significantly between noses and hollows at one or more study localities.

The crack tip strain field of AISI 4340 Part II Experimental measurements

Crack tip strain maps have been measured for AISI 4340 high strength steel. No significant creep was observed. The measured values of CTOD were greater than expected from the HRR model. Crack tip branching was observed in every experiment. The direction of crack branching was in the same direction as a major ridge'' of epsilon(yy) strain, which in turn was in the same direction as predicted by the HRR model. Furthermore, the measured magnitudes of the epsilon(y)y strain in this same direction were in general greater than the values predicted by the HRR model. This indicates more plasticity in the crack tip region than expected from the HRR model. This greater plasticity could be related to the larger than expected CTOD values. The following discrepancies between the measured strain fields for AISI 4340 and the HRR predictions are noteworthy: (1) The crack branching. (2) Values of CTOD significantly higher than predicted by HRR. (3) The major ridge'' of epsilon(yy) strain an angle of about 60 degrees with the direction of overall propagation of the fatigue precrack, in which the measured magnitudes of the epsilon(yy) strain were greater than the values predicted by the HRR model. (4) Asymmetric shape of the plastic zone as measured by the epsilon(yy) strain. (5) Values of shear strain gamma(xy) significantly higher than predicted by the HRR model. (C) 1999 Kluwer Academic Publishers.

Manganese and methane in hydrothermal plumes along the East Pacific Rise, 8°40′ to 11°50′N

In November, 1991, we surveyed the water column for hydrothermal plumes along 350 km of the East Pacific Rise axis from 8°40′ to 11°50′N, using a combination of physical and chemical measurements. Our survey included the two major ridge segments north and south of the Clipperton Transform Fault at about 10°10′N, both limbs of the overlapping spreading centers (OSC's) at 9°03′N and 11°45′N, and a 30-km section of the next ridge segment to the south. We found vigorous plumes along most of this ridge axis, in keeping with its magmatically robust cross-section, axial summit caldera, and shallow, magma-related seismic reflector. These plumes were detectable by both physical (temperature and light attenuation) and chemical (dissolved Mn and CH 4) measurements, although the chemical measurements were more sensitive. The least active sections were the southern third of the northern segment from 10°20 to 52′N and the OSCs, especially the OSC at 11°45′N. Plumes there had weak Mn and CH 4 signals and were barely detectable by physical methods. These axial sections were the only ones surveyed that lie deeper than 2600 m and appear to be magma starved. The most active sections on the northern segment gave stronger signals for Mn and temperature than for CH 4 and light attenuation, whereas the opposite was true on the southern segment, which was the site of a volcanic eruption at 9°45–52′N only seven months prior to our cruise. On the northern segment the four physical and chemical plume tracers correlated positively and linearly with one another, suggesting that the segment was fed by relatively uniform end-member fluids with a mean CH 4 Mn molar ratio of 0.075. The southernmost section surveyed, from 8°42′ to 9°08′N, closely resembled the northern segment. The rest of the southern segment fell into three sections with different CH 4 Mn ratios: 9°39 to 53′N with CH 4 Mn as high as 10, 9°08 to 39′N with CH 4 Mn of 0.51, and 9°53′ to 10°07′N with CH 4 Mn of 0.85. The section with the highest CH 4 Mn was the site of the volcanic eruption, which produced high-temperature, low-salinity, gas-rich vent fluids carrying abundant bacterial particles. The high CH 4 concentrations are clearly associated with the volcanic eruption, but the origin of the CH 4 is unclear.

Chemical and isotopic variations along the superfast spreading East Pacific Rise from 6 to 30�S

Chemical data of 39 fresh basaltic glasses from the East Pacific Rise (EPR) between 6 and 30°S and Pb, Sr, and Nd isotopic compositions of 12 basalt glasses are presented. Major and trace element data indicate a wide compositional range, including primitive basalts (Mg#=0.67) and highly evolved FeTi-basalts (Mg#=0.34) [molMg/(Mg+Fe2+)]. The compositional range can be attributed to low-pressure fractional crystallization. Fractionation-corrected major element concentrations provide evidence for varying mantle melting conditions. Calculations of the melting conditions suggest melt generation in a rising upper mantle column between 20 and 10 kbar, at temperatures between 1430 and 1280°C, and total degrees of partial melting between 17 and 20% by weight. Leached and hand-picked basalt glasses display large variations in 87Sr/86Sr (0.70235–0.70270), 143Nd/144Nd (0.51312–0.51323), and 206Pb/204Pb (18.064–18.665), but are similar to other N-type MORB from the EPR. The isotopic ratios of basalts from 13 to 23°S show strong correlations and delineate two systematic trends. From 23 to 17°S, 87Sr/86Sr and Pb isotope ratios increase and 143Nd/144Nd decrease in agreement with previous results (Mahoney et al. 1989). A reverse trend is indicated by basalts from 17 to 13°S. However, K/Ti and (La/Sm)N continuously increase from 23 to 13°S. This opposite behavior indicates a recent decoupling of isotopic and minor element ratios in the mantle between 13 and 17°S. North of 13.5°S (Garrett Fracture Zone), isotopic data show no systematic variation with ridge location and display an overall weaker covariation. The results suggest that the isotopic variations and ridge segmentation appear to be unrelated and that major ridge offsets apparently coincide with changes in mantle melting conditions (P, T, F) (F, degrees of melting). There is no evidence for a systematic relationship between calculated melting conditions and second order ridge segmentation. Our isotopic data provide further evidence for regionally confined chemical variations in the mantle at 5 to 30°S. We interpret the isotopic trends as reflecting melting of distinct smallvolume and old enriched mantle components. In contrast, variations in trace elements are attributed to young mantle differentiation processes.