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U.S. geomorphologists and biogeographers often cite early theoretical roots dating back to late nineteenth- and early twentieth-century exemplars such as Powell, Gilbert, Cowles, and Clements, or earlier European contributors like Hutton, Lyell, von Humboldt, and, of course, Darwin. Yet reviews of our intellectual roots often overlook an early and important U.S. contributor: George Perkins Marsh. Marsh's work on Man and Nature is more often cited in the field of environmental history, where it is appropriately noted as a prescient review of human impacts on the landscape. We suggest, however, that his significance extends beyond early environmental activism and that in fact Marsh describes many concepts and analytical approaches that continue to underlie modern geomorphology and biogeography. Moreover, Marsh's ideas and approach presaged fundamental concepts central to our current study of the Anthropocene and coupled human–environment systems, as he emphasized interconnections among biotic, geomorphic and human elements, perhaps most notably with regard to impacts of deforestation on flood regimes. There is, therefore, much to learn from Marsh—both about early thinking in physical geography and about the depth of scientific analysis underlying our discipline's early interest in human impacts. [ABSTRACT FROM AUTHOR]

Coastal wetland responses to sea-level rise are greatly influenced by biogeomorphic processes that affect wetland surface elevation. Small changes in elevation relative to sea level can lead to comparatively large changes in ecosystem structure, function, and stability. The surface elevation table-marker horizon (SET-MH) approach is being used globally to quantify the relative contributions of processes affecting wetland elevation change. Historically, SET-MH measurements have been obtained at local scales to address site-specific research questions. However, in the face of accelerated sea-level rise, there is an increasing need for elevation change network data that can be incorporated into regional ecological models and vulnerability assessments. In particular, there is a need for long-term, high-temporal resolution data that are strategically distributed across ecologically-relevant abiotic gradients. Here, we quantify the distribution of SET-MH stations along the northern Gulf of Mexico coast (USA) across political boundaries (states), wetland habitats, and ecologically-relevant abiotic gradients (i.e., gradients in temperature, precipitation, elevation, and relative sea-level rise). Our analyses identify areas with high SET-MH station densities as well as areas with notable gaps. Salt marshes, intermediate elevations, and colder areas with high rainfall have a high number of stations, while salt flat ecosystems, certain elevation zones, the mangrove-marsh ecotone, and hypersaline coastal areas with low rainfall have fewer stations. Due to rapid rates of wetland loss and relative sea-level rise, the state of Louisiana has the most extensive SET-MH station network in the region, and we provide several recent examples where data from Louisiana’s network have been used to assess and compare wetland vulnerability to sea-level rise. Our findings represent the first attempt to examine spatial gaps in SET-MH coverage across abiotic gradients. Our analyses can be used to transform a broadly disseminated and unplanned collection of SET-MH stations into a coordinated and strategic regional network. This regional network would provide data for predicting and preparing for the responses of coastal wetlands to accelerated sea-level rise and other aspects of global change. [ABSTRACT FROM AUTHOR]

Abstract: In a short communication, Huang et al. (2013) presented arguments for invalidating the expanded Lane's relation that we proposed in Dust and Wohl (2012) and reproposed their approach for modifying the balance schematic of the Lane's relation that they first proposed in Nanson and Huang (2008). We contend that their arguments do not invalidate any aspect of the expanded Lane's relation that we proposed and find, conversely, key aspects of their proposed alternative approach problematic. We provide detailed counter arguments for their key points regarding our proposed expanded Lane's relation and for their proposed alternative approach. [Copyright &y& Elsevier]

Rock varnish from late to latest Pleistocene geomorphic features in the drylands of the western U.S. provides evidence of nine millennial-scale wet events from 11,500-18,000 calendar yr B.P., represented by regionally replicable and approximately evenly spaced manganeseand barium-rich dark bands in varnish microstratigraphy. Preliminary radiometric age calibration indicates that these events appear to be broadly coeval with millennial-scale cooling events identified in the Greenland Ice Sheet Project 2 (GISP2) ice core record. Six of these wet events are associated with the cold intervals of the Younger Dryas and Heinrich event H1, and the other three with the short-lived cooling phases of the Intra-Allerød Cold Period, the Older Dryas, and the Oldest Dryas. These results, combined with our previous documentation of millennial-scale wet events in the Holocene varnish record for the same region, indicate that such wet oscillations in the western U.S. may be parts of regionally widespread manifestation of well-documented, pervasive millennial-scale cycles of the North Atlantic climate. [ABSTRACT FROM AUTHOR]

Geophysical and drill-hole data within the Reelfoot rift of Arkansas, Tennessee, Missouri, and Kentucky, USA, were integrated to create a structure contour map and threedimensional computer model of the top of the Precambrian crystalline basement. The basement map and model clearly define the northeast- trending Cambrian Reelfoot rift, which is crosscut by southeast-trending basement faults. The Reelfoot rift consists of two major basins, separated by an intrarift uplift, that are further subdivided into eight subbasins bound by northeast- and southeast-striking rift faults. The rift is bound to the south by the White River fault zone and to the north by the Reelfoot normal fault. The modern Reelfoot thrust fault, responsible for most of the New Madrid seismic zone earthquakes, is interpreted as an inverted basement normal fault. Geologic interpretation of 5077 shallow borings in the central Mississippi River valley enabled the construction of a structure contour map of the Pliocene-Pleistocene unconformity (top of the Eocene-base of Mississippi River alluvium) that overlies most of the Reelfoot rift. This map reveals both river erosion and tectonic deformation. Deformation of the Pliocene-Pleistocene unconformity appears to be controlled by the northeast- and southeast-trending basement faults. The northeast-trending rift faults have undergone and continue to undergo Quaternary dextral transpression. This has resulted in displacement of two major rift blocks and formation of the Lake County uplift, Joiner ridge, and the southern half of Crowley's Ridge as compressional stepover zones that appear to have originated above basement fault intersections. The Lake County uplift has been tectonically active over the past ~2400 yr and corresponds with a major segment of the New Madrid seismic zone. The aseismic Joiner ridge and the southern portion of Crowley's Ridge may reflect earlier uplift, thus indicating Quaternary strain migration within the Reelfoot rift. [ABSTRACT FROM AUTHOR]

Abstract: Statistical analysis of rock glaciers in the Lemhi Range demonstrates that their development and preservation is controlled primarily by annual insolation and lithology. We inspected 171 alpine valleys in the Lemhi Range using optical remote sensing techniques, digital topographic analysis, and field examination. In those valleys, we identified 48 rock glaciers and examined them for lichen cover, evidence of ice presence, specific evidence of movement, and distinctive morphological features. In addition to recording the presence or absence of a rock glacier in each alpine valley, existing rock glaciers were classified according to their morphology. Factors such as topographic shading, lithology, relief, aspect, and elevation determine the development and preservation of rock glaciers. Analysis of these factors in the Lemhi Range shows that elevation >2600 m, a north-facing aspect (300–60°), and <2300 h of direct sunlight per year are necessary conditions for the existence of rock glaciers in any form. The majority of alpine valleys in the Lemhi Range meet these requirements. Thus, other parameters, including topographic shading and lithology, must determine occurrence of rock glaciers in the Lemhi Range. Multivariate statistical analysis of controlling parameters demonstrates that annual insolation and latitude influence rock glacier occurrence most strongly. Whereas duration of insolation is a logical controlling factor, latitude is more enigmatic. Additional statistical analysis indicates that the latitude factor is likely a reflection of lithologic changes with latitude along the range. Lithology may affect rock glacier distribution through its effects on hydrology or air ventilation. Moreover, statistical analysis shows that rock glacier occurrence correlates with protalus lobe occurrence, suggesting that protalus lobes play a role in the genesis of rock glaciers in the Lemhi Range. Separate analysis of the classification systems shows that each morphologic class, inferred to correlate with rock glacier activity, is statistically significant and distinguishable from other classes. In addition to the effect of insolation, statistical analysis of the classification system also shows that latitude influences distribution of existing rock glacier classes independent of lithology. [Copyright &y& Elsevier]

Abstract: The Ratcliff Site in southwestern Virginia lies in a small second-order stream valley filled with approximately 3.5 m of organic-rich deposits that contain bones of mammoth, mastodon, deer (or antelope), logs, and plant macrofossils. Radiocarbon analyses indicate the age of the organic-rich sediment ranges from >44,000 to 29,100 14C yr BP, a time period with no fossil remains reported in this region of the Appalachians. Analyses of field observations, textural data, organic carbon content, and plant macrofossils indicate that the organic-rich sediments contain interbedded standing-water and debris-flow deposits. Up to 6 m of oxidized debris-flow sediments bury the organic-rich sediments. The presence of Rubus parviflorus (Thimble Berry) throughout the deposit indicates the site had a boreal environment from >44,000 to 29,100 14C yr BP. Plant macrofossil evidence indicates the uplands had stands of spruce/jack-pine forests while the valley contained ponds and associated wetlands. Three debris flows occurred at the site between approximately 38,000 and 29,000 14C yr BP, suggesting a recurrence interval for major storms of approximately 3000 yr, even though the apparent stability of the boreal environment implies a climate not conducive to catastrophic rainstorms. This conflicting combination of features suggests that during the middle Wisconsinan this area experienced generally cool climates, dominated by polar air masses, but was punctuated by relatively brief warm periods marked by incursions of tropical air masses. [Copyright &y& Elsevier]

1. Studies of North American streams have shown that hydraulic parameters and stream geomorphology can explain unionid mussel abundance at both the reach and catchment scale. However, few studies have examined applicability of hydrogeomorphic variables across broader spatial scales, such as across whole catchments, or have elucidated conditions under which spates can affect mussel populations in streams. 2. We quantified freshwater mussel abundance and species richness and their physical habitat at 24 sites in eight streams in southern Appalachian catchments in 2000 and 2001. In addition, we modelled site-specific hydraulic parameters during summer baseflow and bankfull stages to estimate high- and low-discharge conditions, respectively. 3. Mussel abundance was related to stream geomorphology, whereas richness was related to stream size. Baseflow habitat parameters explained only minor variation in abundance or richness, and both measures were highly correlated with mean current velocity or stream size. Bankfull shear stress composed a relatively low proportion of overall mussel habitat variability, but it accounted for significant variation in abundance and richness. 4. Mussel abundance was highly variable at sites subject to low-shear stress during spates, whereas abundance always was low at sites subject to high-shear stress. These data suggest that habitat conditions during floods, rather than those at summer baseflow, limit the abundance of mussels in Appalachian streams. These data also suggest that mussel abundance and assemblage structure may be sensitive to any changes in channel geomorphology and hydraulic conditions that might result from land use in the catchment. [ABSTRACT FROM AUTHOR]

Historical sources indicate that, in the late 19th century, the portion of the southern California coastline between Palos Verdes Peninsula and San Mateo Point was composed of a series of barrier spits backed by estuaries, beaches backed by cliffs, and occasional rocky headlands. Nearly natural conditions, a reflection of minimal human impact, prevailed during this relatively stormy interval. US Coast [and Geodetic] Survey materials, early scientific work, newspaper articles, and the accounts of travelers provide much of the information utilized to reconstruct the shoreline. Serving as a major roadway, the beach that extended between San Juan Creek and San Mateo Creek was especially well known. The barrier spits were capped by low dunes and were separated by migrating inlets connecting the ocean with the backing estuaries. Rivers discharged into the estuaries at times, decreasing salinities and depositing sediments. Rocky coastlines are believed to have experienced substantial erosion as high levels of bioerosion and vigorous attack by storm waves is inferred, giving rise to notched cliffs, sea caves, and other erosional forms. Forming part of the seaward fringe of the greater Los Angeles region, today this shoreline is completely developed, serving the commercial and recreational needs of millions of residents and visitors. [ABSTRACT FROM AUTHOR]

The article discusses issues related coastal geomorphology in the U.S. It should be noted that there continues to be a clear trend away from the centrality of geomorphology and geography. It even appears that coastal geomorphologists are no longer publishing in major geomorphology journals. There is little evidence to suggest that coastal geomorphology is making significant contributions to the broader theoretical framework of geomorphology. The author offers some commentary on the position of coastal geomorphology within Geomorphology and Physical Geography, based on the progress made over the last three years.

Focuses on the effects of weather and climate impact on human activities in the U.S. Usage of climate data and information on broad range of social, economic and environmental applications; Implications of heat waves on lifestyles and health of affected population.

Scarp morphology evolution has commonly been used to estimate the timing of fault-scarp rupture events. However, rates of scarp degradation depend strongly on the geomorphic diffusivity, a parameter that is difficult to constrain independently. This difficulty may lead to large uncertainties in the estimated ages of rupture events. In this study, we have coupled the accumulation of the cosmogenic nuclide 36Cl to a model for scarp morphology in order to constrain the value of the geomorphic diffusivity and thus determine a more accurate rupture chronology than a rupture history based solely on scarp morphology. We measured depth profiles of 36Cl accumulated in situ within alluvial sediments beneath the surface of the Socorro Canyon fault scarp in central New Mexico. The material analyzed consisted of ∼150 individual gravel clasts from each depth interval, amalgamated into a single sample. The alluvium was sampled in three vertical profiles ∼4 m deep. The first profile was ∼1.5 m downslope of the fault plane on the hanging wall, the second ∼1.5 m upslope of the fault plane on the footwall, and the third ∼27 m upslope of the fault plane on the footwall. The third profile, which served as a control, and which soil geomorphic evidence indicated was beneath a stable surface, showed a simple exponential 36Cl profile from which a depositional age of 122±18 ka was calculated. The second profile (on the footwall) showed a 36Cl deficit relative to the control profile, indicating net erosion. The first profile (on the hanging wall) showed a 36Cl excess relative to the control profile, indicating net deposition. Stratigraphic evidence in the hanging wall indicated two rupture events prior to the Late Holocene. We modeled the accumulation of 36Cl in the vicinity of the scarp, simulating erosional redistribution using a diffusion equation for scarp morphology. The model accounted for redistribution of 36Cl along with the sediment and the effects of the changing fault-scarp morphology on the 36Cl production. By matching both the observed hanging-wall and footwall 36Cl profiles to profiles calculated by the model, as well as the observed topographic profile, we obtained ages of 92+16−13 and 28+18−23 ka for the two ruptures. The results of our study indicate that cosmogenic nuclides can be useful in constraining rupture chronologies of fault scarps in alluvium. [Copyright &y& Elsevier]

Two Woodfordian glaciated regions in Wisconsin were analyzed to determine the impact of variable loess thickness and contrasting till texture on soil pattern and landscape properties. Each region consisted of a ground moraine/end moraine/outwash plain landform sequence. Data were compiled from soil and topographic maps. In addition to using standard methods of soilscape analysis. I used a natural soil drainage index, calculated from taxonomic data, to determine regional variability and pattern of soil wetness. Results indicate that soilscape variation within each region was large. There were no statistically significant differences, therefore, that could be attributed to known soil- forming processes or to parent material variability. Stratifying the data by geomorphic subregion rather than by region reduced the within-unit soil variability and resulted in numerous significant soilscape differences between subregions. The implication is that soilscape variability is large at the regional scale but converges rapidly with decreasing size of study area. [ABSTRACT FROM AUTHOR]

Channel networks near Inez, Kentucky, were surveyed in the field within 29 small drainage basins that appeared on 1:24,000-scale maps to be unbranched (first order), The basins contained from 0 to 5 channel sources, with an average of 2.15 per basin. Many channel characteristics measured in the field are well correlated with morphometric variables measured from maps, but a substantial proportion of the variance remains unexplained. Although simple correlations are fairly strong for geometric characteristics, they are relatively weak (yet statistically significant) for topological measures. The spatial and temporal persistence of the empirical predictive relations is as yet unknown. [ABSTRACT FROM AUTHOR]

Studies relict tree stumps rooted in present-day lakes, marshes and streams, which suggests that California's Sierra Nevada and Argentina and Chile's Patagonia experienced extremely severe drought conditions during medieval times. Presence of low runoff from the Sierra; Factors which caused the droughts; Implications for future natural or anthropogenically induced warming.

The article presents an analysis on the spatial aspect of geomorphology, particularly at the macro-scale and physiographic regionalism in the United States. The exogenic processes produces changes of landscapes and the formation of different forms of topography. The re-evaluation of physiographic region introduces a precise spatial unit of geomography which is helpful in understanding the changes in the earth.

Focuses on the implications of the decline of the interest in physical geography for the progress in geography in the U.S. Expansion of the field of geography; Development of geomorphology; Plan of the Geological Society of America to establish a Division of Geomorphology.

Explores the physiographic divisions of the U.S. Explanations concerning the need of natural divisions; Details of the work of the Association of American Geographers; Account of the designation by professor W. M. Davis of dominant factors in topography.

The article focuses on The Conference on the Delineation of Physiographic Provinces in the United States, held by the Association of American Geographers. The purpose of this round table conference was to afford opportunity for a free discussion of the problems involved in the division of the area of the United States into physiographic provinces, with a special view to ascertaining whether collaboration in that work by a number of geographers under the leadership of a committee of the association might prove advisable and practicable.

This article focuses on the use of citation indices in comparing geography programs with reference to a study by B.L. Turner and William B. Meyer. In this study, the citation indices are used to rank the quality of U.S. geography departments. The data from SCI and SSCI suggest that the overlap between SCI and SSCI is more serious than Turner and Meyer indicate. They point out that several individuals with the same initials and surnames may appear under the same entry. The conclusion that well-cited individuals tend to publish a lot is true as it stands, based on limited observations in physical geography.

Focuses on training in the field of geomorphology. Graduate work in geography; Physiography of the U.S.