determining soil moisture and sediment availability at white sands dune field new mexico from apparent thermal inertia data 1 determinations of soil moisture and sediment availability in arid regions are important indicators of local climate variability and the potential for future dust storm events data from the advanced spaceborne thermal emission and reflection aster radiometer were used to derive the relationships among potential soil erosion soil moisture and thermal inertia ti at the spatial scale of aeolian landforms for the white sands dune field between may 2000 and march 2008 land surface apparent thermal inertia ati data were used to derive an approximation of actual ti in order to estimate the wind threshold velocity ratio wtr the wtr is a ratio of the wind velocity thresholds at which soil erosion occurs for wet soil versus dry soil the aster derived soil moisture retrievals and the changes through time at white sands were interpreted to be driven primarily by precipitation but the presence of a perched groundwater table may also influence certain areas the sediment availability of dunes active playa surfaces and the margin of the alluvial fans to the west were determined to be consistently higher than the surrounding area the sediment availability can be primarily explained by precipitation events and the number of dry days prior to the data acquisition other factors such as vegetation and the amount of surface crusting may also influence soil mobility but these were not measured in the field this approach showed the highest modeled sediment availability values just days prior to the largest dust emission event at white sands in decades such an approach could be extended to a global monitoring technique for arid land systems that are prone to dust storms and for other regional land surface studies in the sahara

regional aeolian dynamics and sand mixing in the gran desierto evidence from landsat thematic mapper images spatial variations in sand composition were mapped on a regional scale in a terrestrial sand sea the gran desierto of sonora mexico mesoscale mapping on a satellite image base allowed quantitative interpretation of the dynamic development of sand sheets and dunes the results were used to interpret the quaternary geologic history of the tectonically active region at the mouth of the colorado river landsat thematic mapper multispectral images were used to predict the abundance of different mineralogies of sand grains in a mixed aeolian terrain a spectral mixing model separated the effects of vegetation and topographically induced shading and shadow from the effects produced by different mineral and rock types compositions determined remotely agreed well with samples from selected areas within the spectral limitations of the thematic mapper a simple discrimination capability for active versus inactive sand surfaces is demonstrated based upon differences in the percentage of low albedo accessory grains occurring on dormant aeolian surfaces a technique for discriminating between low albedo materials and macroscopic shade is implemented by combining thermal images with the results of the spectral mixing model the image analysis revealed important compositional variations over large areas that were not readily apparent in the field

changes in active eolian sand at northern coachella valley california abstract climate variability and rapid urbanization have influenced the sand environments in the northern coachella valley throughout the late 20th century this paper addresses changes in the spatial relationships among different sand deposits at northern coachella valley between two recent time periods by using satellite data acquired from the advanced spaceborne thermal emission and reflection radiometer aster the approach employed here involving multispectral thermal infrared tir data and spectral mixture analysis has shown that the major sand deposits can be spatially modeled at northern coachella valley the coarse grained quartz rich sand deposit is associated with active eolian sand and the mixed sandy soil and fine grained quartz rich sand deposits are associated with inactive eolian sand the fractional abundance images showed a significant decrease between 2000 and 2006 in the percentage of active sand in the major depositional area for fluvial sediment the whitewater river but also in two downwind areas the whitewater and willow hole reserves the pattern of the active sand appears to be related to variations in annual precipitation wet and dry years and river discharge in the northern coachella valley we suggest here that recent human modifications to the major watercourses that supply sand affect the capability of fluvial deposition areas to restore sediments over time and consequently the responses of the sand transport system to climate change becoming more sensitive to dry years where areas of active sand may shrink degrade and or stabilize faster the approach utilized in this study can be advantageous for future monitoring of sand in the northern coachella valley for management of these and similar environments

preferential dust sources a geomorphological classification designed for use in global dust cycle models received 11 april 2011 revised 28 september 2011 accepted 4 october 2011 published 24 december 2011 1 we present a simple theoretical land surface classification that can be used to determine the location and temporal behavior of preferential sources of terrestrial dust emissions the classification also provides information about the likely nature of the sediments their erodibility and the likelihood that they will generate emissions under given conditions the scheme is based on the dual notions of geomorphic type and connectivity between geomorphic units we demonstrate that the scheme can be used to map potential modern day dust sources in the chihuahuan desert the lake eyre basin and the taklamakan through comparison with observed dust emissions we show that the scheme provides a reasonable prediction of areas of emission in the chihuahuan desert and in the lake eyre basin the classification is also applied to point source data from the western sahara to enable comparison of the relative importance of different land surfaces for dust emissions we indicate how the scheme could be used to provide an improved characterization of preferential dust sources in global dust cycle models

links between topography wind deflation lakes and dust the case of the bodele depression chad the bodele depression chad is the planet s largest single source of dust deflation from the bodele could be seen as a simple coincidence of two key prerequisites strong surface winds and a large source of suitable sediment but here we hypothesise that long term links between topography winds deflation and dust ensure the maintenance of the dust source such that these two apparently coincidental key ingredients are connected by land atmosphere processes with topography acting as the overall controlling agent we use a variety of observational and numerical techniques including a regional climate model to show that 1 contemporary deflation from the bodele is delineated by topography and a surface wind stress maximum 2 the tibesti and ennedi mountains play a key role in the generation of the erosive winds in the form of the bodele low level jet llj 3 enhanced deflation from a stronger bodele llj during drier phases for example the last glacial maximum was probably sufficient to create the shallow lake in which diatoms lived during wetter phases such as the holocene pluvial winds may therefore have helped to create the depression in which erodible diatom material accumulated instead of a simple coincidence of nature dust from the world s largest source may result from the operation of long term processes on paleo timescales which have led to ideal conditions for dust generation in the world s largest dust source similar processes plausibly operate in other dust hotspots in topographic depressions

thermal infrared analysis of weathered granitic rock compositions in the sacaton mountains arizona implications for petrologic classifications from thermal infrared remote sensing data 1 critical to spectral interpretations of geologic surfaces on the earth and mars is an understanding of the relationship between the composition of weathered rock surfaces and whole rock mineralogy in this study thermal infrared spectroscopic and remote sensing analyses were used to determine the composition of weathered granitoid rock surfaces in the sacaton mountains arizona a linear spectral deconvolution approach was employed to determine the mineralogies of naturally exposed weathered surfaces and artificially exposed fresh rock surfaces deconvolution results from fresh rock surfaces yield similar bulk mineralogy to results from point counting of rock slabs and thin sections deconvolution of weathered rock spectra indicate that compared to fresh samples weathered surfaces are deficient in plagioclase feldspar and are enriched in clay minerals the differential weathering of feldspar minerals impacts the interpretation of whole rock mineralogy and the spectral classification of bedrock geology which for plutonic rocks is dependent on the relative proportions of different feldspars deconvolutions of multispectral remote sensing or laboratory data show a deficiency of total feldspar in the weathered rock units but lack sufficient spectral resolution for the discrimination between different feldspars these results demonstrate that the differential breakdown and removal of primary minerals in rock surfaces due to weathering can affect the interpreted rock petrology from remote sensing studies the relationships observed in our granitic samples could be applied to any rock type and may be important to consider for remote sensing of mars

surface mineral mapping at steamboat springs nevada usa with multi wavelength thermal infrared images abstract the purpose of this study was to evaluate the use of airborne multispectral and hyperspectral thermal infrared tir image data for mapping surface minerals characteristic of active geothermal systems tir image data from the master multispectral spectrometer and the sebass hyperspectral spectrometer were acquired over steamboat springs nevada usa in september 1999 spectral emissivity information was extracted from the data and used to generate mineral maps using the master data it was possible to map the extent of the active geothermal area as well as silica rich vs clay rich areas using the sebass data the same areas could be mapped and additionally the presence of several minerals including opal quartz alunite anorthite albite and kaolinite could be identified the sebass data also detected previously unidentified hydrous sulfate minerals tamarugite and alunogen forming around active fumaroles laboratory spectral data and xrd analyses of field samples confirmed the dominant mineral phases identified remotely the airborne field and laboratory data together with temperature anomaly and fumarole location data from other studies were synthesized and linked to the surface geology to determine the diagnostic surface mineral expression that could be mapped with tir remotely sensed data for future exploration for similar geothermal systems opaline sinter deposits are the most diagnostic surface expression of hot spring activity at steamboat springs because they represent areas of the recent geyser activity the differentiation between opal and chalcedony deposits and the identification of hydrous sulfate minerals forming around active fumaroles are also important because chalcedony represents ancient sinter deposits and hydrous sulfate minerals indicate locations of fumaroles that may be venting diffusely with no geyser activity the surface expression of the geothermal system at steamboat springs is small which emphasizes the need for high spatial resolution airborne imagers the 90 m pixels of aster tir data over the same area were only capable of resolving the area of past and recent sinter deposits together master multispectral tir data covered the entire area 12 km 2 at 5 m spatial resolution and were capable of defining the extent of the sinter deposits and zones of hydrothermally altered rocks the sebass image swath was too narrow 256 m to add significant spatial information to the overall map but the high spectral content identified several important minerals related to the local geology and the mineralogic surface expression of the geothermal system

lithologic mapping in the mountain pass california area using advanced spaceborne thermal emission and reflection radiometer aster data abstract evaluation of an advanced spaceborne thermal emission and reflection radiometer aster image of the mountain pass california area indicates that several important lithologic groups can be mapped in areas with good exposure by using spectral matching techniques the three visible and six near infrared bands which have 15 m and 30 m resolution respectively were calibrated by using in situ measurements of spectral reflectance calcitic rocks were distinguished from dolomitic rocks by using matched filter processing in which image spectra were used as references for selected spectral categories skarn deposits and associated bright coarse marble were mapped in contact metamorphic zones related to intrusion of mesozoic and tertiary granodioritic rocks fe muscovite which is common in these intrusive rocks was distinguished from al muscovite present in granitic gneisses and mesozoic granite quartzose rocks were readily discriminated and carbonate rocks were mapped as a single broad unit through analysis of the 90 m resolution five band surface emissivity data which is produced as a standard product at the eros data center three additional classes resulting from spectral angle mapper processing ranged from 1 a broad granitic rock class 2 to predominately granodioritic rocks and 3 a more mafic class consisting mainly of mafic gneiss amphibolite and variable mixtures of carbonate rocks and silicate rocks

aeolian responses to climate variability during the past century on mesquite lake playa mojave desert abstract the erosion and deposition of sediments by wind from 1901 to 2013 have created large changes in surface features of mesquite lake playa in the mojave desert the decadal scale recurrence of sand sheet development migration and merging with older dunes appears related to decadal climatic changes of drought and wetness as recorded in the precipitation history of the mojave desert complemented by modeled soil moisture index values historical aerial photographs repeat land photographs and satellite images document the presence and northward migration of a mid 20th century sand sheet that formed during a severe regional drought that coincided with a multi decadal cool phase of the pacific decadal oscillation pdo the sand sheet slowly eroded during the wetter conditions of the subsequent pdo warm phase 1977 1998 due to a lack of added sediment sand cohesion gradually increased in the sand sheet by seasonal additions of salt and clay and by re precipitation of gypsum which resulted in the wind carving of yardangs in the receding sand sheet smaller yardangs were aerodynamically shaped from coppice dunes with salt clay crusts and larger yardangs were carved along the walls and floor of trough blowouts evidence of a 19th century cycle of sand sheet formation and erosion is indicated by remnants of yardangs photographed in 1901 and 1916 that were found buried in the mid 20th century sand sheet three years of erosion measurements on the playa yardangs and sand sheets document relatively rapid wind erosion the playa has lowered 20 to 40 cm since the mid 20th century and a shallow deflation basin has developed since 1999 annually 5 10 cm of surface sediment was removed from yardang flanks by a combination of wind abrasion deflation and mass movement the most effective erosional processes are wind stripping of thin crusts that form on the yardang surfaces after rain events and the slumping of sediment blocks from yardang flanks these wind eroded landforms persist several decades to a century before eroding away or being buried by younger sands on mesquite lake playa the climatic history of alternating pdo phases of multi decadal drought and wetness is recorded twice by the presence of yardangs formed nearly a century apart

global mineral distributions on mars 1 determining the mineralogy of mars is an essential part of revealing the conditions of the surface and subsurface a deconvolution method was used to remove atmospheric components and determine surface mineralogy from thermal emission spectrometer data at 1 pixel per degree ppd minerals are grouped into categories on the basis of compositional and spectral similarity and global concentration maps are produced all binned pixels are fit well with rms errors of 0 005 in emissivity higher rms errors are attributed to short wavelength particle size effects on dust covered surfaces significant concentrations 0 10 of plagioclase high ca pyroxene sheet silicates high si glass and hematite are detected and display distributions consistent with previous studies elevated concentrations of plagioclase and high ca pyroxene are consistent with basaltic surfaces and are located in low albedo highlands regions north of 45 s significant concentrations of plagioclase and sheet silicates high si glass and low concentrations of high ca pyroxenes are consistent with andesitic surfaces and are concentrated in both southern and northern high latitude low albedo regions andesitic surfaces in the southern hemisphere have a lower spectral contrast than northern surfaces an isolated surface located in solis planum is spectrally distinct but compositionally similar to other surfaces interpreted to be andesitic in composition concentrations of olivine below the detection limit correctly identify its presence in two of three locations potassium feldspar low ca pyroxene basaltic glass olivine sulfate carbonate quartz and amphibole are not detected with confidence at 1 ppd the results presented here indicate a predominance of volcanic compositions within martian dust free surfaces

eolian dynamics and sediment mixing in the gran desierto mexico determined from thermal infrared spectroscopy and remote sensing data the gran desierto dune field is only partially composed of quartz rich sands from the ancestral colorado river local sources have been previously underestimated as a major source of sand because previous remote sensing studies were limited in their capability to detect silicate minerals compositions of sands were evaluated in this study using a combination of laboratory thermal emission spectroscopy and thermal remote sensing data acquired from the advanced spaceborne thermal emission and reflection radiometer aster instrument the spatial interpolation of sample compositions allowed visualization of the sand transport pathways from feldspar rich local sources by revealing gradients of composition between the dune field and surrounding local sources the laboratory data were comparable to the remote sensing retrievals of quartz and feldspar abundance the mineralogical maturity of the desierto dunes could be determined by the quartz feldspar ratio therefore providing a context for understanding the provenance of the gran desierto in relation to other mojave and sonoran dune fields the composition of a previously undescribed group of dunes east of the pinacate the sonoyta dunes was measured as higher in potassium feldspar relative to the rest of the dune field the composition of sonoyta dunes is characteristic of other mojave dune fields which are more isolated near local feldspar rich sources south of the pinacate quartz rich sand from the west admixes with feldspar rich sand from the sonoyta dunes to the east the northern margin of the gran desierto is similarly enriched in feldspar from alluvial fans and the coastal sand is influenced by carbonate sand that does not appear to survive transport to the inland dunes

soil erosion along a transect in a forested catchment recent or ancient processes abstract forested areas are assumed not to be influenced by erosion processes however forest soils of northern germany in a hummocky ground moraine landscape can sometimes exhibit a very shallow thickness on crest positions and buried soils on slope positions the question consequently is are these on going or ancient erosional and depositional processes plutonium isotopes act as soil erosion deposition tracers for recent last few decades processes here we quantified the 239 240pu inventories in a small forested catchment ancient forest melzower forst deciduous trees which is characterised by a hummocky terrain including a kettle hole soil development depths depth to c horizon and 239 240pu inventories along a catena of sixteen different profiles were determined and correlated to relief parameters moreover we compared different modelling approaches to derive erosion rates from pu data we find a strong relationship between soil development depths distance to sink and topography along the catena fully developed retisols thicknesses 1 m in the colluvium overlay old land surfaces as documented by fossil ah horizons however we found no relationship of pu based erosion rates to any relief parameter instead 239 240pu inventories showed a very high local spatial variability 36 70 bq m 2 low annual rainfall spatially distributed interception and stem flow might explain the high variability of the 239 240pu inventories giving rise to a patchy input pattern different models resulted in quite similar erosion and deposition rates max 5 t ha 1 yr 1 to 7 3 t ha 1 yr 1 although some rates are rather high the magnitude of soil erosion and deposition in terms of soil thickness change is negligible during the last 55 years the partially high values are an effect of the patchy pu deposition on the forest floor this forest has been protected for at least 240 years therefore rather natural events and anthropogenic activities during medieval times or even earlier must have caused the observed soil pattern which documents strong erosion and deposition processes

mapping playa evaporite minerals and associated sediments in death valley california with multispectral thermal infrared images efflorescent salt crusts and associated sediments in death valley california were studied with remote sensing data acquired by the nasa thermal infrared multispectral scanner tims nine spectral classes that represent a variety of surface materials were distinguished including several classes that reflect important aspects of the playa groundwater chemistry and hydrology evaporite crusts containing abundant thenardite sodium sulfate were mapped along the northern and eastern margins of the cottonball basin areas where the inflow waters are rich in sodium gypsum calcium sulfate crusts were more common in the badwater basin particularly near springs associated with calcic groundwaters along the western basin margin evaporite rich crusts generally marked areas where groundwater is periodically near the surface and thus able to replenish the crusts though capillary evaporation detrital silicate minerals were prevalent in other parts of the salt pan where shallow groundwater does not affect the surface composition the surface features in death valley change in response to climatic variations on several different timescales for example salt crusts on low lying mudflats form and redissolve during seasonal to interannual cycles of wetting and desiccation in contrast recent flooding and erosion of rough salt surfaces in death valley probably reflect increased regional precipitation spanning several decades remote sensing observations of playas can provide a means for monitoring changes in evaporite facies and for better understanding the associated climatic processes at present such studies are limited by the availability of suitable airborne scanner data however with the launch of the earth observing system eos am 1 platform in 1998 multispectral visible near infrared and thermal infrared remote sensing data will become globally available

a change detection application on the evolution of kahak playa south khorasan province iran kahak salt playa in south khorasan province of iran have special geomorphological characteristics by the presence of ephemeral saline lakes wetlands salt crusts surface accumulations of salt and zones of patterned ground salt crusts in the soil surface are unique in the region and have laminated horizons in the playa soil soil surface salt accumulations are dominated by nacl and gypsum it has been found that distribution of chemical soluble is not uniform across the playa landscape and this result influences on the variety form of patterned ground in this study the percent changes in some of the chemical elements such as nacl gypsum and also brine extent have been calculated in the playa indicating changes in kahak salt playa is the main aim of this study by using remote sensing and gis techniques in this paper techniques such as spectral un mixing maximum likelihood classification band rationing fuzzy classification and correlation relationships are discussed this contribution presents modeling of temporal and spatial changes of salinity and playa developing using combined approaches that incorporate different data fusion and data integration techniques for two periods of date furthermore percent changes in the surface patterned ground of the playa have been calculated using texture and pattern analysis of the pca1 results have revealed that in the playa developing chemical materials such as sodium nacl gypsum and also brine extent are positively correlated with each other and the most increased changes are related to gypsum and the most decreased changes are related to the nacl also changes in the amount of agricultural area in the playa lakes margin show low effects in the desertification process

surface sediment dynamics in a dust source from spaceborne multispectral thermal infrared data abstract this study utilized spaceborne multispectral thermal infrared tir data to document spatial relationships of surface sediments over time in a modern depositional environment associated with dust emissions soda lake playa mojave desert united states the approach employed here involved time series tir data acquired from advanced spaceborne thermal emission and reflection radiometer aster and a linear spectral mixture analysis an automated algorithm was applied to derive emissivity image endmembers evaluation of the chosen endmembers revealed that they can be categorized into five major spectra classes based on diagnostic absorption features each spectrum has been identified in relation to mineral abundance and soil arrangement that are common in playa settings a clayey silt rich crust b intermediate salt crust c quartz rich deposit d salt rich rough crust e sulfate rich crust spectral classes a b c d yielded the lowest rms errors 0 0 025 over time in the iterative deconvolution algorithm between the measured and modeled spectra the produced fractional abundance images show high areal concentrations for clayey silt rich crust salt rich rough crust and quartz rich deposit as the first surficial mapping of soda lake significant changes in the spatial relationships of the major surface sediments in soda lake were observed after a flooding event 2005 and a relatively dry period 2006 the approach utilized in this study can be advantageous for continuous monitoring of environments characterized by a small area and a complex surface which may enable a better understanding of their responses to climate changes and potential for dust emissions

thermal infrared emission spectroscopy of anhydrous carbonates the objective of this study is to present the thermal emission spectra of various anhydrous calcite and dolomite series carbonate minerals to illustrate the effect of the structural cation ca 2 mg 2 fe 2 mn 2 zn 2 on shifting the positions of the carbonate absorption bands all of the carbonate mineral emission spectra included in this study exhibit three absorption features related to three specific vibrational modes of the carbonate anion co 3 2 these anion vibrations include the out of plane bend the asymmetric stretch and the in plane bend i e the 2 3 and 4 modes respectively the positions of the absorption band emissivity minima are unique for each carbonate chemistry and are thus diagnostic of mineralogy the average 2 3 and 4 wavenumber positions for the various carbonate minerals are as follows calcite caco 3 883 1523 and 712 cm 1 magnesite mgco 3 901 1572 and 748 cm 1 siderite feco 3 876 1523 and 736 cm 1 rhodochrosite mnco 3 877 1535 and 726 cm 1 smithsonite znco 3 882 1509 and 742 cm 1 dolomite camg co 3 2 894 1547 and 728 cm 1 and kutnahorite camn co 3 2 882 1526 and 716 cm 1 carbonates as a general mineral class crystallize in a variety of geological environments however each specific carbonate mineralogy typically is limited to a narrow range of geologic settings in which it forms thermal infrared emission data to be received from the mars global surveyor thermal emission spectrometer will contain the spectral signature of carbonates if they are present above the detectibility limit on the surface of mars this study presents the spectral information necessary to recognize carbonate as a mineral class as well as identify the specific type of carbonate from thermal emissivity data knowledge of distinct carbonate mineralogy will be useful for interpreting the environmental conditions that were present on mars during the carbonate formation the result of this study is that the major carbonate mineral species calcite dolomite magnesite siderite and smithsonite can be identified from thermal infrared emission data provided moderate 10 cm 1 spectral sampling because of the similarity of absorption band positions between kutnahorite and calcite high 2 cm 1 spectral sampling is required to distinguish kutnahorite moderate spectral sampling data are also sufficient to determine the amount of mg and fe in mg fe solid solution minerals to within 3 5 of the cation abundance

monitoring salt playa dynamics using thematic mapper data various image analysis techniques have been applied to multitemporal landsat thematic mapper data collected over a four year period the results have been used to monitor sediment transport processes in semi arid south central tunisia process domains on salt playas in the study area have been identified and mapped seasonal interseasonal and spatial changes on these playas have been related to sediment salt and moisture regimes surface water and groundwater activity and eolian processes are identified as important sediment transport processes the observations bring into question the traditional groundwater based model of salt playa geochemistry a revised set of integrated geochemical geomorphological models is invoked

lithologic mapping of the mordor nt australia ultramafic complex by using the advanced spaceborne thermal emission and reflection radiometer aster abstract spectral measurements made in the mordor pound nt australia study area using the advanced spaceborne thermal emission and reflection radiometer aster in the laboratory and in situ show dominantly al oh and ferric iron vnir swir absorption features in felsic rock spectra and ferrous iron and fe mg oh features in the mafic ultramafic rock spectra aster ratio images matched filter and spectral angle mapper processing sam were evaluated for mapping the lithologies matched filter processing in which vnir swir image spectra were used for reference resulted in 4 felsic classes and 4 mafic ultramafic classes based on al oh or fe mg oh absorption features and in some subtle reflectance differences related to differential weathering and vegetation these results were similar to those obtained by match filter analysis of hymap data from a previous study but the units were more clearly demarcated in the hymap image aster tir spectral emittance data and laboratory emissivity measurements document a wide wavelength range of si o spectral features which reflect the lithological diversity of the mordor ultramafic complex and adjacent rocks sam processing of the spectral emittance data distinguished 2 classes representing the mafic ultramafic rocks and 4 classes comprising the quartzose to intermediate composition rocks utilization of the complementary attributes of the spectral reflectance and spectral emittance data resulted in discrimination of 4 mafic ultramafic categories 3 categories of alluvial colluvial deposits and a significantly more completely mapped quartzite unit than could be accomplished by using either data set alone

the temporal variability of centimeter scale surface roughness in a playa dust source synthetic aperture radar investigation of playa surface dynamics abstract emission of mineral dust aerosols is highly dynamic in part due to variability in surface erodibility investigation of the variations of surfaces within dust source regions has the potential to elucidate the processes that control erodibility and to improve model representations of dust emission in this study we investigate surface temporal variability in the black rock playa nevada usa using synthetic aperture radar sar satellite data from between 2004 and 2010 the sar backscatter 0 observations of the playa surface are compared to weather station observations and temporally resolved measurements of water inundation derived from multi spectral modis satellite data the data illustrate that centimeter scale surface roughness on the playa is surprisingly heterogeneous over multi meter length scales and evolves dynamically on annual time scales interannual changes in surface roughness on the playa are quite large compared to the variability of surface roughness during the summer months july september suggesting that summer anthropogenic and aeolian processes are substantially less important than water related processes for controlling the evolution of the playa surface playa median 0 is relatively low in years with high annual precipitation 140 mm suggesting that surface water controls centimeter scale surface roughness and potentially erodibility spatially there is a relationship between 0 and the time of year at which a surface dries areas drying in july have significantly higher 0 than surfaces that dry earlier in the year suggesting that spatial heterogeneity in 0 is controlled by cycles of wetting and drying at the edge of the playa lake the implications in the black rock playa and potentially more broadly are that water is a critical factor controlling playa surface evolution and the annual time scale is crucial for investigations of playa erodibility

evanescent wave coupling in a geophysical system airborne acoustic signals from the mw 8 1 macquarie ridge earthquake atmospheric low frequency sound i e infrasound from underwater events has not been considered thus far due to the high impedance contrast of the water air interface making it almost fully reflective here we report for the first time on atmospheric infrasound from a large underwater earthquake mw 8 1 near the macquarie ridge which was recorded at 1325 km from the epicenter seismic waves coupled to hydroacoustic waves at the ocean floor after which the energy entered the sound fixing and ranging channel and was detected on a hydrophone array the energy was diffracted by a seamount and an oceanic ridge which acted as a secondary source into the water column followed by coupling into the atmosphere the latter results from evanescent wave coupling and the attendant anomalous transparency of the sea surface for very low frequency acoustic waves

dust emission from wet and dry playas in the mojave desert usa the interactions between playa hydrology and playa surface sediments are important factors that control the type and amount of dust emitted from playas as a result of wind erosion the production of evaporite minerals during evaporative loss of near surface ground water results in both the creation and maintenance of several centimeters or more of loose sediment on and near the surfaces of wet playas observations that characterize the texture mineralogic composition and hardness of playa surfaces at franklin lake soda lake and west cronese lake playas in the mojave desert california along with imaging of dust emission using automated digital photography indicate that these kinds of surface sediment are highly susceptible to dust emission the surfaces of wet playas are dynamic surface texture and sediment availability to wind erosion change rapidly primarily in response to fluctuations in water table depth rainfall and rates of evaporation in contrast dry playas are characterized by ground water at depth consequently dry playas commonly have hard surfaces that produce little or no dust if undisturbed except for transient silt and clay deposited on surfaces by wind and water although not the dominant type of global dust salt rich dusts from wet playas may be important with respect to radiative properties of dust plumes atmospheric chemistry windborne nutrients and human health published in 2007 by john wiley sons ltd

mapping playa evaporite minerals with aviris data a first report from death valley california abstract efflorescent salt crusts in death valley california were mapped by using airborne visible infrared imaging spectrometer aviris data and a recently developed least squares spectral band fitting algorithm eight different saline minerals were remotely identified including three borates hydroboracite pinnoite and rivadavite that have not been previously reported from the death valley efflorescent crusts the three borates are locally important phases in the crusts and at least one of the minerals rivadavite appears to be forming directly from brine borates and other evaporite minerals provide a basis for making remote chemical measurements of desert hydrologic systems for example in the eagle borax spring area the aviris mineral maps pointed to elevated magnesium and boron levels in the ground waters and to the action of chemical divides causing subsurface fractionation of calcium many other chemical aspects of playa brines should have an expression in the associated evaporite assemblages certain anhydrous evaporites including anhydrite glauberite and thenardite lack absorption bands in the visible and near infrared wavelength range and crusts composed of these minerals could not be characterized by using aviris in these situations thermal infrared remote sensing data may complement visible and near infrared data for mapping evaporites another problem occurred in wet areas of death valley where water absorption caused low signal levels in the 2 0 2 5 m wavelength region that obscured any spectral features of evaporite minerals despite these difficulties the results of this study demonstrate the potential for using aviris and other imaging spectrometer data to study playa chemistry such data can be useful for understanding chemical linkages between evaporites and ground waters and will facilitate studies of how desert ground water regimes change through time in response to climatic and other variables

identification of sand sources and transport pathways at the kelso dunes california using thermal infrared remote sensing the kelso dune field is located in the eastern mojave desert california at the terminus of a sand transport pathway which has its primary source at the mojave river wash 50 km to the west initial examination of 1984 airborne thermal infrared multispectral scanner tims data showed significant spectral variations that indicate potential mineralogic heterogeneities within the active dunes this result prompted the collection of a suite of 48 sand samples in 1990 and the acquiring of new tims data in 1995 this new data set was used to test a newly developed linear spectral retrieval algorithm in conjunction with a spectral library of end member minerals results of this analysis produced images of end member minerals that showed marked variations within the dunes in addition standard petrographic techniques revealed that the dunes contain mineralogic variations and were much less quartz rich 42 than previously reported 70 90 point count results agreed with the spectral data to within an average of 5 3 for tims derived and 3 1 for laboratory derived mineralogic abundances high concentrations of several of the end member minerals on the surrounding alluvial fans indicate a potential nearby source for these minerals most evident is the presence of potassium feldspar from the fan that emanates from the providence mountains east of the dunes this previously unidentified potential sand input is not visible with other remote sensing techniques and was confirmed with additional field sampling much of the quartz and some plagioclase feldspar however appear to have been transported from the mojave river wash source as previously reported this study also validates the potential of using thermal remote sensing from future satellite based instruments to globally monitor desert fringe areas susceptible to the changing conditions of sand encroachment