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Coastal erosion can be a serious issue requiring accurate observations in order to evaluate vulnerable areas and determine the subsequent actions to address this problem. The Town of Bay Bulls, [...]

Predicting the retreat of a coastal soft cliff is a difficult and uncertain operation, which has both theoretical and practical significance. Recession of soft cliffs occurs through a combination of processes, including slope failures and surface erosion, that are difficult to model jointly. Deterministic models for predicting coastal retreat are hampered by the complex nature of coastal erosion, which is highly nonuniform in space and episodic in time. To overcome these limitations, stochastic approaches have been proposed. These models assume distributions for the size and the time of the recession events. In this paper we investigate the frequency-size statistics of soft-cliff erosion based on two historical datasets of coastal retreat measurements at two sites in England. We find that the two datasets exhibit a similar behavior. The frequency of the recessions decreases with increasing size of the retreat. For small retreats the decrease is slow. For medium to large retreats the decrease is rapid and follows a power law. The frequency-size statistics of soft-cliff erosion is similar to the statistics of medium to large landslide areas, which are also power-law distributed. This is a significant but not conclusive result. More data are needed to confirm this finding. DOI: 10.1061/(ASCE)0733-950X(2005)131:1(37) CE Database subject headings: Cliffs; Erosion; Coastal environment; Statistics.

Laboratory experiments have been performed to investigate the recession of soft cliffs due to oblique wave actions. The experiments were conducted in a wave tank with irregular waves. A test cliff was constructed of wet sand and (in one test) a sand/clay mixture, which was found to be appropriate for simulating the principal failure mode of soft cliffs fronted by erodeable beaches. The recession process is characterized by the following sequence: toe erosion--cliff failure--erosion of debris--toe erosion. The recession of the cliff top was measured from still photographs taken by an overhead camera. The longshore and cross-shore extents of individual failures and the time interval between two successive failures are obtained. CE Database subject headings: Cliffs; Erosion; Failure modes.

The 20 September 1899 Menderes earthquake was the most damaging event that has occurred in the Buyuk Menderes graben in the last 100 years. The earthquake involved normal faulting along the northern margin of the Buyuk Menderes graben from west of Aydin to Nazilli. A detailed investigation along the northern margin of the graben showed the presence of faults cutting actively depositing graben floor deposits in the foot of Neogene hills. Along an E-W trend east of Aydin, a normal fault was located having an observable length of at least 3 km and a maximum vertical displacement of about 3.5 m. A stream entering to the graben changed its cause due to this fault. Field evidence suggests that, in addition to south-side down-throw by as much as 2 m during the 1899 event, there was also at least 1.5 m opening along the surface break. Field evidence also showed that the 1899 surface break follows a pre-existing break which might have ruptured during the 26 (or 25) BC and 22 February 1653 events: again south-side down-thrown by at least 1 m and 1.5 m, respectively. Keywords: Turkey, Holocene, faulting, earthquake, geomorphology.

Cosmogenic 36Cl concentrations in basalt samples from the Drakensberg escarpment on the SE African passive margin give quantitative estimates of denudation and scarp retreat rates. Over the [10.sup.4]-[10.sup.6] year timespan addressed by these data, the calculated escarpment retreat rate has been 50-95 m [Ma.sup.-1] and the average summit denudation rate 6 m [Ma.sup.-1]. The scarp retreat rate is an order of magnitude less than previously suggested. The rate of summit lowering is sufficient to prevent the long-term intact survival of erosion cycle surfaces formed in the Mesozoic that were previously inferred for this region. Keywords: SE Africa, cosmogenic isotopes, denudation, landscapes, scarps.

It has been suggested that rock climbing in some national parks may reduce the nesting success of some bird species, including birds of prey, but little research exists to substantiate such claims. A new study of rock climbing and bird communities at Joshua Tree National Park, CA, is presented. The study finds no differences in numbers of bird taxa among different climbing categories but only the more common bird species were found at climbed cliffs. Birds' use of unclimbed cliffs was greater than for climbed cliffs, while more birds were seen flying at climbed cliffs.

(1) Along the Niagara Escarpment in Ontario, Canada, a stunted forest of old-growth Thuja occidentalis occurs on cliff faces, but is replaced by a deciduous forest dominated by Acer saccharum within 5 m of the cliff edge on the upper plateau. (2) The stem frequencies of all seedling and sapling size-classes of Thuja decreased with distance from the cliff, but for Acer the smallest size classes displayed the greatest increase in stem frequency away from the cliff edge. (3) Seed input did not change significantly across the cliff-edge--deciduous-forest continuum for either species. (4) Recruitment patterns of the two species differed significantly across the gradient. Seed emergence of Thuja was limited by litter in the deciduous forest but not at the cliff edge. Herbivory restricted recruitment of Acer more at the cliff edge than in the deciduous forest. (5) The maintenance of the spatial pattern appears to be due to an array of interacting factors which change across the environmental gradient and over time.

Vegetation differences between pristine cliffs and cliffs subjected to rock-climbing were found to be the result not of climbing disturbance but to climber choice of cliffs with less vegetation. Implications for rock-climbing development and conservation management are discussed.

The functional dependence of bedrock conversion to soil on the overlying soil depth (the soil production function) has been widely recognized as essential to understanding landscape evolution, but was quantified only recently. Here we report soil production rates for the first time at the base of a retreating escarpment, on the soil-mantled hilly slopes in the upper Bega Valley, southeastern Australia. Concentrations of [sup.10]Be and [sup.26]Al in bedrock from the base of the soil column show that soil production rates decline exponentially with increasing soil depth. These data define a soil production function with a maximum soil production rate of 53 m/m.y. under no soil mantle and a minimum of 7 m/m.y. under 100 cm of soil, thus constraining landscape evolution rates subsequent to escarpment retreat. The form of this function is supported by an inverse linear relationship between topographic curvature and soil depth that also suggests that simple creep does not adequately characterize the hillslope processes. Spatial variation of soil production shows a landscape out of dynamic equilibrium, possibly in response to the propagation of the escarpment through the field area within the past few million years. In addition, we present a method that tests the assumption of locally constant soil depth and lowering rates using concentrations of [sup.10]Be and [sup.26]Al on the surfaces of emergent tors. Keywords: erosion, cosmogenic nuclides, landscape evolution, geomorphology, tors.

The lower part of the Campanian Castlegate Formation, one of the best known fluvial sheet sands of the Western Interior seaway, combines with an overlying finer grained unit (middle member of the Castlegate Formation) to form an unconformity-bounded, third-order stratigraphic sequence (~3 m.y. duration). This sequence contains a mappable muddy zone along the western Book Cliffs of Utah now mapped as contiguous with the open-marine parts of the succession (Buck Tongue, Sego Sandstone, Anchor Mine Tongue) to the east. The correlation within the middle Castlegate has been refined and the nature of the link between tidally influenced fluvial strata in the west and marine strata in the east has been remapped. Five high-frequency stratigraphic sequences (all within the upper part of the larger third-order sequence), forming a thickness to 160 m, have been mapped in the Price area southeastward into the time-equivalent marine succession near Green River. Individual sequences (probably [is less than] 0.5 m.y. duration), reflecting transgressive to regressive estuary infilling, have an internal architecture in which fluvial and tidally influenced distributary-channel belts pass up into muddy central-basin sedimentary units, to bayhead-delta deposits, and in some places up to more fluvial channel belts. The key to the mapping of individual sequences is recognition of the muddy, brackish-water interval, developed during maximum transgression of the time-equivalent shoreline. The two most proximal marine-influenced sequences (2 and 3) are probably broadly time-equivalent with the Buck and Anchor Mine Tongues to the east. The analysis here, contrary to recent suggestions, shows that the marine sequences in the eastern Book Cliffs can be traced far into the time-equivalent, western fluvio-estuarine succession. Keywords: Castlegate, Book Cliffs, nonmarine, sequence stratigraphy.