volcanic ash hazard to aviation during the 2003 2004 eruptive activity of anatahan volcano commonwealth of the northern mariana islands abstract within the commonwealth of the northern mariana islands cnmi anatahan is one of nine active subaerial volcanoes that pose hazards to major air traffic routes from airborne volcanic ash the 2003 2004 eruptive activity of anatahan volcano affected the region s aviation operations for 3 days in may 2003 on the first day of the eruption 10 may 2003 two international flights from saipan to japan were cancelled and several flights implemented ash avoidance procedures on 13 may 2003 a high altitude flight through volcanic gas was reported with no perceptible damage to the aircraft toms and modis analysis of satellite data strongly suggests that no significant ash and only minor amounts of so 2 were involved in the incident consistent with crew observations on 23 may 2003 airport operations were disrupted when tropical cyclone winds dispersed ash to the south dusting saipan with light ashfall and causing flight cancellations there and at guam 320 km south of the volcano operational near real time monitoring of ash clouds produced by anatahan has been conducted since the first day of the eruption on 10 may 2003 by the washington volcanic ash advisory center vaac the vaac was among the first groups outside of the immediate area of the volcano to detect and report on the unexpected eruption of anatahan after being contacted about an unusual cloud by national weather service forecasters in guam at 1235 utc on 10 may 2003 the vaac analyzed goes 9 images confirming anatahan as the likely source of an ash cloud and estimating that the eruption began at about 0730 utc the vaac issued its first volcanic ash advisory for anatahan at 1300 utc on 10 may 2003 more than 5 h after the start of the eruption the delay reflecting the difficulty of detecting and confirming a surprise eruption at a remote volcano with no in situ real time geophysical monitoring the initial eruption plume reached 10 7 13 4 km 35 000 44 000 ft well into jet cruise altitudes thereafter the maximum plume height decreased and during the rest of the eruption usually did not exceed 5 km 17 000 ft which lessened the potential hazard to aircraft at higher cruise altitudes drifting ash clouds commonly extended hundreds of kilometers from the volcano occasionally as far west as the philippines over the course of the eruptive activity in 2003 2004 the vaac issued 323 advisories 168 with graphical depictions of ash clouds for anatahan serving as a reliable source of ash cloud information for aviation related meteorological offices and air carriers with a record of frequent eruptions in the cnmi continued satellite and in situ real time geophysical monitoring is needed at anatahan and other marianas volcanoes so that potential hazards to aviation from any future eruptive activity can be quickly and correctly assessed

shatter cones and planar deformation features confirm santa marta in piaui state brazil as an impact structure a total of 184 confirmed impact structures are known on earth to date as registered by the earth impact database the discovery of new impact structures has progressed in recent years at a rather low rate of about two structures per year here we introduce the discovery of the approximately 10 km diameter santa marta impact structure in piau i state in northeastern brazil santa marta is a moderately sized complex crater structure with a raised rim and an off center approximately 3 2 km wide central elevated area interpreted to coincide with the central uplift of the impact structure the santa marta structure was first recognized in remote sensing imagery and later by distinct gravity and magnetic anomalies here we provide results obtained during the first detailed ground survey the bouguer anomaly map shows a transition from a positive to a negative anomaly within the structure along a ne sw trend which may be associated with the basement signature and in parts with the signature developed after the crater was formed macroscopic evidence for impact in the form of shatter cones has been found in situ at the base around the central elevated plateau and also in the interior of fractured conglomerate boulders occurring on the floor of the surrounding annular basin planar deformation features pdfs are abundant in sandstones of the central elevated plateau and at scattered locations in the inner part of the ring syncline together shatter cones and pdfs provide definitive shock evidence that confirms the impact origin of santa marta crystallographic orientations of pdfs occurring in multiple sets in quartz grains are indicative of peak shock pressures of 20 25 gpa in the rocks exposed at present in the interior of the crater in contrast to recent studies that have used additional and sometimes highly controversial alleged shock recognition features santa marta was identified based on well understood traditional shock evidence

modeling the capacity of riverscapes to support beaver dams abstract the construction of beaver dams facilitates a suite of hydrologic hydraulic geomorphic and ecological feedbacks that increase stream complexity and channel floodplain connectivity that benefit aquatic and terrestrial biota depending on where beaver build dams within a drainage network they impact lateral and longitudinal connectivity by introducing roughness elements that fundamentally change the timing delivery and storage of water sediment nutrients and organic matter while the local effects of beaver dams on streams are well understood broader coverage network models that predict where beaver dams can be built and highlight their impacts on connectivity across diverse drainage networks are lacking here we present a capacity model to assess the limits of riverscapes to support dam building activities by beaver across physiographically diverse landscapes we estimated dam capacity with freely and nationally available inputs to evaluate seven lines of evidence 1 reliable water source 2 riparian vegetation conducive to foraging and dam building 3 vegetation within 100 m of edge of stream to support expansion of dam complexes and maintain large colonies 4 likelihood that channel spanning dams could be built during low flows 5 the likelihood that a beaver dam is likely to withstand typical floods 6 a suitable stream gradient that is neither too low to limit dam density nor too high to preclude the building or persistence of dams and 7 a suitable river that is not too large to restrict dam building or persistence fuzzy inference systems were used to combine these controlling factors in a framework that explicitly also accounts for model uncertainty the model was run for 40 561 km of streams in utah usa and portions of surrounding states predicting an overall network capacity of 356 294 dams at an average capacity of 8 8 dams km we validated model performance using 2852 observed dams across 1947 km of streams the model showed excellent agreement with observed dam densities where beaver dams were present model performance was spatially coherent and logical with electivity indices that effectively segregated capacity categories that is beaver dams were not found where the model predicted no dams could be supported beaver avoided segments that were predicted to support rare or occasional densities and beaver preferentially occupied and built dams in areas predicted to have pervasive dam densities the resulting spatially explicit reach scale 250 m long reaches data identifies where dam building activity is sustainable and at what densities dams can occur across a landscape as such model outputs can be used to determine where channel floodplain and wetland connectivity are likely to persist or expand by promoting increases in beaver dam densities

sedimentation rates and patterns in beaver ponds in a mountain environment abstract sediment depth was measured at several sites within each of eight beaver ponds in glacier national park montana and sediment samples wen collected from five of these ponds accumulation rates of sediments far exceeded published rates from boreal forest landscapes in eastem and central north america pond area strongly predicts volume of sedimentation textural differences illustrated spatial variations associated with position in a pond and along a pond sequence organic matter content was significantly higher in older ponds and has ramifications for the development of the benthos and the long term storage of matter in ponds the role of beavers as biogeomorphic agents is profound but requires further elucidation to distinguish between fluvial sediment deposition in ponds and sediment deposition associated with beaver excavational activity

integrated satellite observations of the 2001 eruption of mt cleveland alaska abstract satellite data were the primary source of information for the eruption of mt cleveland alaska on 19 february and 11 and 19 march 2001 multiple data sets were used pre syn and post eruption to mitigate the hazard and determine an eruption chronology the 19 february eruption was the largest of the three resulting in a volcanic cloud that formed an arc over 1000 km long moved to the ne across alaska and was tracked using satellite data over more than a 50 h period the volcanic cloud was concurrently detected on the goes avhrr and modis data at various times and their respective signals compared all three sensors detected a cloud that had a very similar shape and position but there were differences in their areal extent and internal structural detail goes data showed the largest volcanic cloud in terms of area probably due to its oblique geometry modis bands 31 and 32 which are comparable to goes and avhrr thermal infrared wavelengths were the least effective single channels at detecting the volcanic cloud of those investigated modis bands 28 29 31 and 32 modis bands 28 and 29 detected the largest volcanic clouds that could easily be distinguished from weather clouds of the split window data modis bands 29 minus band 32 detected the largest cloud but the band 31 minus band 32 data showed the volcanic cloud with the most internal structural detail the puff tracking model accurately tracked the movement and predicted the extent and shape of this complex cloud even into areas beyond satellite detection numerous thermal anomalies were also observed during the eruption on the twice daily avhrr data and the high spatial resolution landsat data the high resolution radarsat data showed that the avhrr thermal anomalies were due to lava and debris flow features and a newly formed fan along the west coast of the island field observations and images from a hand held forward looking infrared radiometer flir showed that the flow features were a a lava debris flows and a warm debris fan along the west coast real time satellite data were the primary tool used to monitor the eruption track changes and to mitigate hazards high resolution data even though coverage is infrequent were critical in helping to identify volcanic processes and to compile an eruption chronology

antecedent controls on river character and behaviour in partly confined valley settings upper hunter catchment nsw australia abstract a partly confined river is one along which the contemporary channel abuts the valley margin along 10 90 of its length they occur along sections of longitudinal profiles that are transitional from fully bedrock confined to fully alluvial rivers at this position in the landscape there is sufficient accommodation space for discontinuous floodplain pockets to form segregation of the river s load and dissipation of flow energy result in sediments being stored outside the channel bedrock and planform controlled variants of these rivers and associated floodplains are differentiated terraces fans and piedmont zones act as secondary confining features on channel planform and floodplain formation in these valleys the influence of these antecedent features on contemporary river character and behaviour in partly confined valleys of the upper hunter catchment new south wales australia is appraised the balance of formative and reworking processes and associated capacity for geomorphic adjustment is influenced by the site specific configuration of antecedent controls at any floodplain pocket downstream patterns of these river types are analysed along all major tributaries of the upper hunter catchment to highlight the extent of antecedent control on contemporary river forms and processes in this landscape setting

remote observations of eruptive clouds and surface thermal activity during the 2009 eruption of redoubt volcano abstract volcanoes often erupt explosively and generate a variety of hazards including volcanic ash clouds and gaseous plumes these clouds and plumes are a significant hazard to the aviation industry and the ground features can be a major hazard to local communities here we provide a chronology of the 2009 redoubt volcano eruption using frequent low spatial resolution thermal infrared tir mid infrared mir and ultraviolet uv satellite remote sensing data the first explosion of the 2009 eruption of redoubt volcano occurred on march 15 2009 utc and was followed by a series of magmatic explosive events starting on march 23 utc from march 23 april 4 2009 satellites imaged at least 19 separate explosive events that sent ash clouds up to 18 km above sea level asl that dispersed ash across the cook inlet region in this manuscript we provide an overview of the ash clouds and plumes from the 19 explosive events detailing their cloud top heights and discussing the variations in infrared absorption signals we show that the timing of the tir data relative to the event end time was critical for inferring the tir derived height and true cloud top height the ash clouds were high in water content likely in the form of ice which masked the negative tir brightness temperature difference btd signal typically used for volcanic ash detection the analysis shown here illustrates the utility of remote sensing data during volcanic crises to measure critical real time parameters such as cloud top heights changes in ground based thermal activity and plume cloud location

caliop observations of the transport of ash from the eyjafjallajokull volcano in april 2010 1 the cloud aerosol lidar with orthogonal polarization caliop is an elastic backscatter lidar carried on the calipso satellite caliop observations between 15 and 20 april 2010 of volcanic ash plumes following the eruption of the icelandic eyjafjallajokull volcano are reported here while caliop has limited spatial coverage due to nadir only sampling ash plumes were observed by caliop over a wide region from the north atlantic ocean to eastern europe during both day and night due to its nadir only view however caliop did not sample the densest ash plumes which were observed by passive satellite sensors and ground based lidar lidar depolarization and spectral backscatter signatures are used to discriminate ash layers from clouds most ash was observed in thin layers of laminar appearance with thicknesses ranging from 0 4 km to a little more than 1 km and at relatively low altitudes between 1 and 7 km most layers reported here produced strong lidar depolarization indicating a predominance of ash over sulfate aerosol in the plumes estimates of lidar extinction to backscatter ratio allow the retrieval of profiles of ash optical properties layers were observed with mean optical extinction ranging from 0 03 km 1 to nearly 1 km 1 combined with an estimate of mass extinction efficiency mass concentration profiles can also be estimated these observations of the three dimensional dispersion of the plume are complementary to observations from passive satellite instruments and ground based lidars and can be useful for verification of dispersion models such as those used by the volcanic ash advisory centers

improved prediction and tracking of volcanic ash clouds abstract during the past 30 years more than 100 airplanes have inadvertently flown through clouds of volcanic ash from erupting volcanoes such encounters have caused millions of dollars in damage to the aircraft and have endangered the lives of tens of thousands of passengers in a few severe cases total engine failure resulted when ash was ingested into turbines and coating turbine blades these incidents have prompted the establishment of cooperative efforts by the international civil aviation organization and the volcanological community to provide rapid notification of eruptive activity and to monitor and forecast the trajectories of ash clouds so that they can be avoided by air traffic ash cloud properties such as plume height ash concentration and three dimensional ash distribution have been monitored through non conventional remote sensing techniques that are under active development forecasting the trajectories of ash clouds has required the development of volcanic ash transport and dispersion models that can calculate the path of an ash cloud over the scale of a continent or a hemisphere volcanological inputs to these models such as plume height mass eruption rate eruption duration ash distribution with altitude and grain size distribution must be assigned in real time during an event often with limited observations databases and protocols are currently being developed that allow for rapid assignment of such source parameters in this paper we summarize how an interdisciplinary working group on eruption source parameters has been instigating research to improve upon the current understanding of volcanic ash cloud characterization and predictions improved predictions of ash cloud movement and air fall will aid in making better hazard assessments for aviation and for public health and air quality

introduction to the special issue connectivity in geomorphology abstract with the increased recent attention on understanding the complex pathways and fluxes of material energy and organisms and the multidimensional coupling between various geomorphic process domains the 47th binghamton geomorphology symposium was organized around the theme of connectivity in geomorphology six key subthemes emerged sediment connectivity hydrologic connectivity geochemical connectivity riverine connectivity landscape connectivity and modeling of connectivity papers presented at the symposium and collected in this special issue elucidate the theoretical and conceptual underpinnings of connectivity but also provide field based and analytical approaches to document the fundamental role of connectivity in geomorphic and ecological functioning among the consistent themes that emerged from the papers and from discussion during the symposium were 1 the interconnectedness of diverse forms of connectivity 2 the appropriateness or not of conceptualizing connectivity as a gradient or continuum and 3 the importance of an explicit recognition of disconnectivity as a mechanism to retain ecologically important materials and organisms within landscapes knowledge gaps identified in discussions during the symposium include identifying questions that can be usefully addressed within a framework emphasizing connectivity identifying feedbacks that enhance and limit connectivity and quantification of diverse aspects of connectivity of thresholds of connectivity and of interactions among different types of connectivity

holocene beaver damming fluvial geomorphology and climate in yellowstone national park wyoming abstract we use beaver pond deposits and geomorphic characteristics of small streams to assess long term effects of beavers and climate change on holocene fluvial activity in northern yellowstone national park although beaver damming has been considered a viable mechanism for major aggradation of mountain stream valleys this has not been previously tested with stratigraphic and geochronologic data thirty nine radiocarbon ages on beaver pond deposits fall primarily within the last 4000 yr but gaps in dated beaver occupation from 2200 1800 and 950 750 cal yr bp correspond with severe droughts that likely caused low to ephemeral discharges in smaller streams as in modern severe drought maximum channel gradient for reaches with holocene beaver pond deposits decreases with increasing basin area implying that stream power limits beaver damming and pond sediment preservation in northern yellowstone the patchy distribution and cumulative thickness of mostly

rivers in the anthropocene the u s perspective abstract during the past 50 yr the number and variety of papers written by u s fluvial geomorphologists that examine human alterations of rivers has accelerated substantially from an initial focus primarily on how human induced changes in land cover influence sediment yield and river dynamics the literature has expanded to emphasize the effects of flow regulation channel engineering removal of large wood and beavers and changing climate these multiple human influences are now widely recognized to have resulted in global scale cumulative effects including significantly altered fluxes of water sediment nitrogen and carbon and complete transformation of river networks across much of the planet one outgrowth of this recognition is the increasing involvement of geomorphologists in diverse forms of river restoration a form of river management that thus far has largely been dominated by engineers acknowledging the ubiquity of human alteration of rivers implies that i investigators cannot assume that even the most remote and seemingly pristine river segment has not been affected at least indirectly by people ii the use of reference conditions requires careful consideration with respect to what reference sites indicate about past conditions as well as their relevance for the future iii detailed geomorphic understanding of the nature and timing of past human alterations of rivers is likely to be critical to effective restoration and iv each scientist must decide how to engage within the context of research and advocacy with the issues of ecosystem degradation and loss of river form and function

simulating the dispersal of tephra from the 1991 pinatubo eruption implications for the formation of widespread ash layers abstract puff and hazmap two tephra dispersal models developed for volcanic hazard mitigation are used to simulate the climatic 1991 eruption of mt pinatubo puff simulations indicate that the majority of ash was advected away from the source at the level of the tropopause 17 km several eruptive pulses injected ash and so2 gas to higher altitudes 25 km but these pulses represent only a small fraction 1 of the total erupted material released during the simulation comparison with toms images of the so2 cloud after 71 and 93 h indicate that the so2 gas originated at an altitude of 25 km near the source and descended to an altitude of 22 km as the cloud moved across the indian ocean hazmap simulations indicate that the pinatubo tephra fall deposit in the south china sea was formed by an eruption cloud with the majority of the ash concentrated at a height of 16 18 km results of this study demonstrate that the largest concentration of distal ash was transported at a level significantly below the maximum eruption column height 40 km and at a level below the calculated height of neutral buoyancy 25 km simulations showed that distal ash transport was dominated by atmospheric circulation patterns near the regional tropopause in contrast the movement of the so2 cloud occurred at higher levels along slightly different trajectories and may have resulted from gas particle segregations that took place during intrusion of the pinatubo umbrella cloud as it moved away from source

beaver dams and channel sediment dynamics on odell creek centennial valley montana usa abstract beaver dams in streams are generally considered to increase bed elevation through in channel sediment storage thus reintroductions of beaver are increasingly employed as a restoration tool to repair incised stream channels here we consider hydrologic and geomorphic characteristics of the study stream in relation to in channel sediment storage promoted by beaver dams we also document the persistence of sediment in the channel following breaching of dams nine reaches containing 46 cross sections were investigated on odell creek at red rock lakes national wildlife refuge centennial valley montana odell creek has a snowmelt dominated hydrograph and peak flows between 2 and 10 m 3 s 1 odell creek flows down a fluvial fan with a decreasing gradient 0 018 0 004 but is confined between terraces along most of its length and displays a mostly single thread variably sinuous channel the study reaches represent the overall downstream decrease in gradient and sediment size and include three stages of beaver damming 1 active 2 built and breached in the last decade and 3 undammed in channel sediment characteristics and storage were investigated using pebble counts fine sediment depth measurements sediment mapping and surveys of dam breaches upstream of dams deposition of fine 2 mm sediment is promoted by reduced water surface slope shear stress and velocity with volumes ranging from 48 to 182 m 3 high flows however can readily transport suspended sediment over active dams variations in bed sediment texture and channel morphology associated with active dams create substantial discontinuities in downstream trends and add to overall channel heterogeneity observations of abandoned dam sites and dam breaches revealed that most sediment stored above beaver dams is quickly evacuated following a breach nonetheless dam remnants trap some sediment promote meandering and facilitate floodplain development persistence of beaver dam sediment within the main channel on odell creek is limited by frequent breaching

leaky rivers implications of the loss of longitudinal fluvial disconnectivity in headwater streams article i nfo naturally induced longitudinal disconnectivity in the form of channel spanning logjams creates backwaters along headwater streams that reduce velocity and transport capacity create at least temporary storage sites for finer sediment and organic matter and enhance biological processing and uptake of nutrients land uses that reduce wood recruitment and instream storage result in reduced stream complexity and in creased longitudinal connectivity in headwater rivers we examine three scales of naturally occurring longi tudinal disconnectivity in headwater streams of the colorado front range and the implications for channel process and form of historical alterations in disconnectivity basin scale disconnectivity at channel lengths of 10 2 10 3 m results from downstream alternations between steep narrowly confined valley segments with single thread channels and lower gradient wider valley segments with multi thread channels this variation in valley geometry likely reflects differences in average spacing between joints in bedrock outcrops which influences bedrock weathering and erosion greater volumes of wood stored in the wide valley seg ments correlate with more closely spaced channel spanning logjams and greater storage of fine sediments and organic matter reach scale disconnectivity at channel lengths of 10 1 10 2 m results from the presence of numerous closely spaced channel spanning logjams which cumulatively store substantial amounts of fine sediment and organic matter the backwater effects associated with an individual jam can result in the accumulation of up to 11 m 3 of fine sediment upstream from the jam of which as much as 21 is organic

identifying eruptive sources of drifting volcanic ash clouds using back trajectory modeling of spaceborne thermal infrared data a new approach is presented for determining the source region of disconnected volcanic ash clouds using a combination of orbital thermal infrared tir image data hysplit generated backward trajectories and spatial geostatistics interpolated surfaces derived from the tir data are created to find the most likely ash cloud travel path and the potential source volcanoes identified from that path the ability to use backward trajectories to determine the ash cloud source region will become an important triggering tool to target high spatial resolution orbital sensors which normally rely on thermal anomalies for new targeting during cases where thermal anomalies are not present or masked by meteorological cloud ash cloud detection and predicted source location become more important image data from several well documented past eruptions are presented to validate and determine the overall accuracy of this technique because this is seen as a limited range source region validation tool the ash clouds examined were 1000 km from their source vent the approach and analysis are deemed successful if 80 of the model results produce one or more trajectories that pass within 60 km of the source volcano this methodology could be improved further with the ability to determine the cloud location more accurately using higher image data frequency and most importantly greater accuracy in determining the cloud height in the atmosphere

geomorphic changes upstream of beaver dams in bridge creek an incised stream channel in the interior columbia river basin eastern oregon channel incision is a widespread phenomenon throughout the dry interior columbia river basin and other semi arid regions of the world which degrades stream habitat by fundamentally altering natural ecological geomorphological and hydrological processes we examined the extent of localized aggradation behind beaver dams on an incised stream in the interior columbia river basin to assess the potential for using beaver castor canadensis dams to restore such channels and the effect of the aggradation on riparian habitat we estimated aggradation rates behind 13 beaver dams between 1 and 6 years old on bridge creek a tributary to the john day river in eastern oregon vertical aggradation rates are initially rapid as high as 0 47 m yr 1 as the entrenched channel fills then level off to 0 075 m yr 1 by year six as the sediment begins accumulating on adjacent terraces we found that a 0 5 m elevation contour above the stream channel approximately coincided with the extent of new riparian vegetation establishment therefore we compared the area surrounding reaches upstream of beaver dams that were within 0 5 m elevation of the stream channel with adjacent reaches where no dams existed we found that there was five times more area within 0 5 m elevation of the channel upstream of beaver dams presumably because sediment accumulation had aggraded the channel our results suggest that restoration strategies that encourage the recolonization of streams by beaver can rapidly expand riparian habitat along incised streams copyright 2007 john wiley sons ltd

classification of the alterations of beaver dams to headwater streams in northeastern connecticut u s a abstract of the many types of barriers to water flow beaver dams are among the smallest typically lasting less than a decade and rarely exceeding 1 5 m in height they are also among the most frequent and common obstructions in rivers with a density often exceeding ten dams per km a frequency of construction within a given network on a time scale of years and a historic extent covering most of north america past quantification of the geomorphologic impact of beaver dams has primarily been limited to local impacts within individual impoundments and is of limited geographic scope to assess the impact of beaver dams at larger scales this study examines channel shape and sediment distribution in thirty river reaches in northeastern connecticut u s a the study reaches fall within the broader categories of impounded and free flowing segments leaving a third segment class of beaver meadows requiring additional study each of the study reaches were classified at the reach scale as free flowing valley wide beaver pond in channel beaver pond and downstream of beaver dam the bankfull channel width to depth ratios and channel widths normalized by watershed area vary significantly across the study reach classes additionally reaches modified by beaver dams have finer sediment distributions this paper provides the first quantitative geomorphic descriptions of the in channel beaver pond and reaches downstream of beaver dams given the different channel shapes and sediment distributions we infer that geomorphic processes are longitudinally decoupled by these frequent barriers that control local base level these barriers generate heterogeneity within a river network by greatly increasing the range of channel morphology and by generating patches controlled by different processes therefore in spite of the small size of individual beaver dams the cumulative effect of multiple dams has the potential to modify processes at larger spatial scales to improve assessment of the larger scale impacts we propose a hierarchical classification scheme based on discontinuities place the reach classes of this study within that scheme and suggest that further research should continue investigation of discontinuity at the network scale and quantification of the cumulative impacts

anatomy of 1986 augustine volcano eruptions as recorded by multispectral image processing of digital avhrr weather satellite data eighteen digital avhrr advanced very high resolution radiometer data sets from noaa 6 and noaa 9 polar orbiting satellites recorded between 27 march and 7 april 1986 depict the eruptive activity of augustine volcano located 280 km sw of anchorage alaska the synoptic view resolution of either 1 1 or 4 4 km frequent coverage often twice a day and multispectral coverage five bands 0 58 0 68 0 72 1 1 3 55 3 93 10 5 11 3 and 11 5 12 5 m makes the avhrr broadly applicable to analyzing explosive eruption clouds the small scale of the augustine activity column heights of 2 13 km and eruption rates of 2x106 8x107 metric tonnes day facilitated intensive multispectral study because the plumes generally covered areas within the 550x550 km area of one easily manipulated image field hourly ground weather data and twice daily radiosonde measurements from stations surrounding the volcano plus numerous volcanological observations were made throughout the eruption providing important ground truth with which to calibrate the satellite data the total erupted volume is estimated to be at least 0 102 km3 the pattern of changing eruption rates determined by satellite observations generally correlate with more detailed estimates of explosion magnitudes multispectral processing techniques were used to distinguish eruption clouds from meteorological clouds variable weather during the augustine eruption offered an opportunity to test various trial algorithms a ratio between thermal ir channels four and five served to delineate the ashbearing eruption plumes from ordinary clouds future work is needed to determine whether the successful multispectral discrimination is caused by wavelength dependent variable emission of silicate ash or reflects a spectral role of sulfuric acid aerosol in the plume

the geomorphic influences of beaver dams and failures of beaver dams abstract uncounted millions of beaver ponds and dams existed in north america prior to european contact and colonization these ponds acted as sediment traps that contained tens to hundreds of billions of cubic meters of sediment that would otherwise have passed through the fluvial system removal of beavers by overtrapping in the 16th 19th centuries severely reduced their number and the number of ponds and dams dam removal altered the fluvial landscape of north america inducing sediment evacuation and entrenchment in concert with widespread reduction in the wetlands environments partial recovery of beaver populations in the 20th century has allowed reoccupation of the entirety of the pre contact range but at densities of only one tenth the numbers nevertheless modern beaver ponds also trap large volumes of sediment in the high hundred millions to low billions of cubic meters range failure of beaver dams is a more common phenomenon than often assumed in the literature during the past 20 years numerous cases of dam failure have been documented that resulted in outburst floods these floods have been responsible for 13 deaths and numerous injuries including significant impacts on railway lines

effects of a beaver pond on runoff processes comparison of two headwater catchments abstract natural variations in concentrations of 18 o d and h 4 sio 4 in two tributary catchments of woods lake in the west central adirondack mountains of new york were measured during 1989 1991 to examine runoff processes and their implications for the neutralization of acidic precipitation by calcium carbonate treatment the two catchments are similar except that one contained a 1 3 ha beaver pond evaporation from the beaver pond caused a seasonal decrease in the slope of the meteoric water line in stream water from the catchment with a beaver pond wo2 no corresponding change in slope of the meteoric water line was evident in stream water from the other catchment wo4 nor in ground water nor soil water from either catchment indicating that evaporative fractionation was not significant application of a best fit sine curve to 18 o data indicated that base flow in both catchments had a residence time of about 100 days ground water from a well finished in thick till had the longest residence time 160 days soil water from the o horizon and b horizon had residence times of 63 and 80 days respectively water previously stored within each catchment pre event water was the predominant component of streamflow during spring snowmelt and during spring and autumn rainfall events but the proportion of streamflow that consisted of pre event water differed significantly in the two catchments the proportion of event water rain and snowmelt in wo2 was smaller than at wo4 early in the spring snowmelt of march 13 17 1990 but the proportions of source water components for the two catchments were almost indistinguishable by the peak flow on the third day of the melt the event water was further separated into surface water and subsurface water components by utilizing measured changes in h 4 sio 4 concentrations in stream water during the snowmelt results indicated that subsurface flow was the dominant pathway by which event water reached the stream except during the peak flow of a rain on snow event on the last day of the melt streamflow from a spring rain storm with dry antecendent conditions two months later may 16 18 1990 was less than 5 event water at peak flow in wo2 and 26 in wo4 this change from the runoff pattern in march is attributed to retention of event water in the beaver pond favored by relatively low pre event storage and isothermal nonstratified conditions in the pond that allowed mixing streamflow during several autumn storms was about 15 25 event water at peak flow in wo4 the highest values for event water were associated with wet antecedent moisture conditions these results indicate that a beaver pond can significantly affect the downstream delivery of event water through evaporation and mixing but provides minimal retention during large runoff events such as snowmelt beaver ponds are expected to provide greater opportunity for neutralization of acidic waters during most of the year in catchments treated with calcium carbonate but little neutralization effect during snowmelt