characteristics of large terrestrial impact structures as revealed by remote sensing studies abstract remote sensing data sets of a spectrum of impact structures on earth have been analyzed in an effort to determine if such structures have identifiable signatures which could be used as an aid in searching broad areas for the missing craters predicted by current estimates of the cratering flux meteor crater arizona has been used as a control site due to the extensive data available for this feature laboratory thermal infrared reflectance spectra of shocked sandstones indicate that shock processes alter the appearance of fundamental absorption features enough to permit such effects to be observed in airborne thermal infrared imagery collected with the nasa tims instrument analysis of this tims imagery suggests that shocked and displaced target rocks can be readily identified aircraft multi frequency imaging radar data collected with the nasa jpl sar polarimeter clearly reveals the textural pattern of the preserved components of the ejecta blanket spot multi spectral imagery of bosumtwi ghana illustrates the difficulties associated with remote sensing in highly vegetated terrains nevertheless the imagery reveals the subtle expression of an outer tectonic ring at the crater and may be sensitive to geobotanical variations associated with impact related suevite deposits in contrast the zhamanshin impact feature on the arid sedimentary plains of kazakhstan is ideal for multi spectral remote sensing although much of the expected morphologic expression of the complex crater is missing or subdued virtually all of the field mapped impact related deposits display a unique spectral pattern in decorrelated landsat thematic mapper imagery the extensive deposits of allogenic breccias which cap the hills defining the inner ring of the crater are very distinctive as are certain of the impact glass deposits a second or outer ring at 13 13 5 km is apparent in the decorrelated principal component tm imagery the suggestion is that spectral disruption patterns for large multi ring impact features in arid settings should be identifiable from orbit by examining a pristine 144 km diameter multi ring impact feature on the venus rolling plains an impression of the original morphology of a continental impact crater of the magnitude of the cretaceous tertiary k t boundary impact structure can be deduced the 35 ma popigai structure is the only known 100 km class impact crater on earth approximately equal in age or younger than the k t event and its morphology is poorly expressed in single band landsat imagery thus spectral anomalies associated with key impact deposits such as allogenic breccias suevite melt and glasses may have to form the basis for identifying candidate k t impact sites in the absence of preserved morphologic elements of the crater it is apparent that remote sensing is not a panacea for the discovery and validation of new impact craters but it can contribute by serving as a pathfinder both for the identification of promising structures and the possible locations of key deposits for detailed fieldwork and sampling

acid weathering of basalt and basaltic glass 2 effects of microscopic alteration textures on spectral properties this work was funded in part by the nasa 2001 mars odyssey themis project jet propulsion laboratory contract 1228404 through arizona state university and by the arizona state university exploration postdoctoral fellowship the natural sciences and engineering research council of canada the canadian space agency the canada foundation for innovation the manitoba research innovations fund and the university of winnipeg for supporting the establishment and operation of the planetary spectrophotometer facility

what can thermal infrared remote sensing of terrestrial volcanoes tell us about processes past and present on mars over the past fifty years a diverse set of thermal infrared tir remote sensing data has been acquired from the orbits of earth and mars which both have ubiquitous volcanic landforms these data vary in spatial spectral and temporal resolution and are critical for investigating an ever expanding set of science applications including the focus of this review paper volcanic processes volcanic studies using tir data include active monitoring of flows and plumes on earth and mapping the compositional and thermophysical diversity on mars furthermore recent advances in high resolution low cost ground and laboratory tir instrumentation now help to augment the orbital data through a synergistic approach to data analysis and validation field and laboratory studies also serve as terrestrially focused analogues that provide important insights to interpret the geologic processes that have operated on other planetary surfaces including mars this review expands upon our invited talk of the same title at the 2014 geological society of america meeting to include several case studies designed to give the reader an overview of how tir data can be applied to volcanic processes on earth and mars these case studies highlight prior work by the authors presented at past meetings but which have not been published elsewhere the examples were chosen specifically to identify the tir data similarities between the two planets and include analyses of volcanic surfaces to 1 derive composition and texture using tir spectra earth and mars 2 analyze mantled flows with thermophysical data earth and mars 3 estimate lava discharge rate using tir derived temperature earth with application to mars and 4 model flow dynamics based on geomorphic measurements mars because of our focus on the tir we do not attempt to document other remote sensing wavelength regions nor even every volcanic study using tir data as tir instruments have improved over time along similar trajectories the higher spatial and spectral resolutions provide the ability to examine volcanic processes in more quantitative ways despite the fact that no tir instrument has ever been designed solely to study volcanic phenomena whether these trends continue for both planets will depend on the design of new tir technologies the data they produce and the science that results from the data

thermal infrared reflectance and emission spectroscopy of quartzofeldspathic glasses 1 this investigation seeks to better understand the thermal infrared tir spectral characteristics of naturally occurring amorphous materials through laboratory synthesis and analysis of glasses because spectra of glass phases differ markedly from their mineral counterparts examination of glasses is important to accurately determine the composition of amorphous surface materials using remote sensing datasets quantitatively characterizing tir 5 25 m spectral changes that accompany structural changes between glasses and mineral crystals provides the means to understand natural glasses on earth and mars a suite of glasses with compositions analogous to common terrestrial volcanic glasses was created and analyzed using tir reflectance and emission techniques documented spectral characteristics provide a basis for comparison with tir spectra of other amorphous materials glasses clays etc our results provide the means to better detect and characterize glasses associated with terrestrial volcanoes as well as contribute toward understanding the nature of amorphous silicates detected on mars

subsidence in the paricutin lava field causes and implications for interpretation of deformation fields at volcanoes abstract assessment of volcanic hazards includes interpretation of ground deformation signal which at polygenetic volcanoes often results from the superposition of deformation due to pressure changes in the magmatic system and due to surficial processes such as cooling of emplaced lava the deformation signal associated with emplaced lava is sometimes considered negligible if fields are decades old but if the lava thickness is great deformation may still be occurring possibly leading to misinterpretation of the observed deformation here i evaluate the 2007 2011 ground motion of the 1943 1952 lava field of the paricutin monogenetic cinder cone mexico interferometric synthetic aperture radar insar time series reveal patchy subsidence restricted to the lava field and following linear rates up to 5 5 cm year there is a clear correlation between subsidence rates and topography suggesting a causal relationship with deposits or lava thickness i estimate these thicknesses in the subsiding areas using pre and post eruption topographic maps and show that they reach up to 200 m a numerical model for lava flow cooling was developed considering radiation and convection from the surface conductive transfer inside the flow and to the ground and vesiculation and latent heat generation at the top and bottom of the flow the model shows that compaction induced by cooling of the thick deposits emplaced 60 years ago explains the observed subsidence when conductive transfer to the ground is considered these results demonstrate that thick deposits can keep deforming significantly even decades after their emplacement emphasizing the importance of considering cooling processes when interpreting deformation fields at polygenetic volcanoes producing massive lava fields

mid infrared spectroscopy of pahala ash palagonite and implications for remote sensing studies of mars remote sensing of mars at mid infrared wavelengths could be used to identify different silicate rocks and minerals current knowledge suggests that the primary components of the surface of mars are basaltlike rocks and a palagonitelike dust to study the mid infrared 7 20 m spectroscopy of this combination of materials we examined the influence of pahala ash palagonite on the biconical reflectance of quartzite and basalt the reflectance of the palagonite is flat and low 1 2 unlike the reflectance of quartzite and basalt the reflectance of quartzite or basalt is significantly reduced by the addition of small amounts of the palagonite dust a dusting of 1 20 m palagonite particles and 20 250 m particle clumps covering 50 of the quartzite host reduces the quartzite mid infrared reflectance by 50 as expected for an essentially black coating similar data were obtained for basalt even for extremely small amounts of palagonite 2 100 m thickness averaging 5 m the reflectance of the underlying rock is linearly related to exposed surface area to confirm the opaque behavior of the pahala ash palagonite coatings we estimated the imaginary part k of the refractive index from transmission measurements the strong absorption and low reflectance high emissivity of the palagonite at 8 11 m and 17 25 m explain its opaque behavior estimates of the extinction coefficient indicate that even a 5 m thickness of pahala ash palagonite is optically thick in these wavelength ranges where silicate rock identification is critical thus mid infrared remote sensing of rocks on mars will be practical only for dust free areas

rock coatings in hawaii basaltic lava flows exposed to semiarid weathering on the island of hawaii develop hydrous silica coatings that thicken and incorporate detrital material with age the nearly pure silica coatings on the younger rocks are colorless but basaltic detritus and its weathering products incorporated into coatings on older flows produce colors ranging from brown to red age rate of supply of material and the mechanical stability of flow surfaces dictate the color and thickness of coatings fresh glassy pahoehoe surfaces support thin as much as 5 m clear silica coatings but break down in a few years to expose the vesicular underlying material at first coloring is concentrated in the open vesicles yielding a dark brown color a mixture of red vesicles and projections of black basalt with age thicker accumulations of silica incorporate layers of oxidized basaltic material the dark basaltic material in kilauea and mauna kea coatings is probably supplied by large explosive eruptions but at mauna loa and kohala the source could be locally derived basaltic weathering products the clear hydrous silica layers are probably the product of leaching of locally derived basaltic dust

thermal infrared satellite measurements of volcanic activity at stromboli and vulcano the use of landsat thermal infrared imagery gives a direct way of quantitatively monitoring the evolution of low amplitude thermal anomalies using nighttime landsat thematic mapper images of vulcano and stromboli volcanoes on october 23 1986 we have developed a simplified method for correcting atmospheric effects we were then able to identify thermal anomalies around the craters part of the stromboli lava flow formed 1 year earlier was also still warm enough to be detected we obtained fairly accurate estimates of relative surface anomaly radiative heat fluxes 29 5 w m 2 21 4 w m 2 and 37 5 w m 2 for the stromboli craters stromboli lava flow and vulcano crater respectively accounting for the convective heat loss significantly increases the estimates of the relative internal heat flux of geothermal origin we found values of 370 60 w m 2 for the stromboli crater region 220 50 w m 2 for the stromboli lava flow and 270 60 w m 2 for the vulcano crater despite the low precision these values are much higher than the 53 62 w m 2 limit defined by cassinis and lechi 1974 as the threshold where the geothermal flux can affect ground temperatures our study provides a unique systematic definition of thermal volcanic features found on stromboli and vulcano the spatial extents of the anomalies and their fluxes and associated errors

quantitative estimation of sio sub 2 content in igneous rocks using thermal infrared spectra with a neural network approach develops a method for estimating the sio sub 2 content of igneous rocks using thermal infrared reflectance spectra aiming to utilize it in the remote sensing of thermal spectral emission silicate minerals which are the major components of the earth s surface display their strongest fundamental molecular vibration bands in the thermal infrared region 8 12 spl mu m the wavelengths of these so called reststrahlen bands are systematically related to the sio sub 2 content of rocks pattern matching using a back propagating neural network approach between simulated remotely sensed data and the sio sub 2 content was performed this approach was evaluated by comparing the spectrally estimated sio sub 2 content with the chemically determined sio sub 2 content for a separate set of rock samples the estimated error between the spectrally estimated and chemically determined sio sub 2 contents for most samples was within 7 future multiband satellite sensors of the earth s thermal emission will have much higher spectral and spatial resolution than existing ones and should be able to detect these spectral trends

numerical modeling of lava flow cooling applied to the 1997 okmok eruption approach and analysis 1 throughout february and march of 1997 okmok volcano in the eastern aleutian islands of alaska erupted a 6 km long lava flow of basaltic a a within its caldera a numerical model for lava flow cooling was developed and applied to the flow to better understand the nature of its cooling radiation and convection from the surface as well as conduction to the ground were used to transport the flow s heat to its surroundings in the model internally a conduction only approach moved heat from the interior outward vesiculation latent heat generation and thermal conductivity changes with temperature are among the other factors that were dynamically accounted for results indicate that ambient temperature fluctuations on the scale of days to weeks must be taken into account to create an accurate short term prediction of lava surface temperature daily data of rainfall and ambient temperature as opposed to yearly averages greatly increased the accuracy of the model furthermore convective cooling of the lava surface was observed to be a dominant heat loss process during the first 200 days indicating the convective heat transfer coefficient is a prime determinant of the accuracy of the model for predicting surface temperatures over a longer cooling period 2 years thermal conductivity and porosity proved to be among the dominating factors for heat loss because of the limiting role of conductive heat flow in the interior the model s flexibility allows application to flows other than the 1997 okmok eruption

timescales and mechanisms of formation of amorphous silica coatings on fresh basalts at kīlauea volcano hawai i young basalts from k lauea volcano hawai i frequently feature opaque surface coatings 1 80 m thick composed of amorphous silica and fe ti oxides these coatings are the product of interaction of the basaltic surface with volcanically derived acidic fluids previous workers have identified these coatings in a variety of contexts on hawai i but the timescales of coating development coating growth rates and factors controlling lateral coating heterogeneity were largely unconstrained we sampled and analyzed young lava flows of varying ages from hours to 40 years along k lauea s southwest and east rift zones to characterize variation in silica coating properties across the landscape coating thickness varies as a function of flow age flow surface type and proximity to acid sources like local fissure vents and regional plumes emitted from k lauea caldera and pu u silica coatings that form in immediate proximity to acid sources are more chemically pure than those forming in higher ph environments which contain significant al and fe incipient siliceous alteration was observed on basalt surfaces as young as 8 days old but periods of a year or more are required to develop contiguous coatings with obvious opaque coloration inferred coating growth rates vary with environmental conditions but were typically 1 5 m year coatings form preferentially on flow surfaces with glassy outer layers such as spatter ramparts volcanic bombs and dense pahoehoe breakouts due to glass strain weakening during cooling microtextural evidence suggests that the silica coatings form both by in situ dissolution reprecipitation and by deposition of silica mobilized in solution thin films of water acidified by contact with volcanic vapors dissolved near surface basalt then precipitated amorphous silica in place mobilizing more soluble cations additional silica was transported to and deposited on the surface by silica bearing altering fluids derived from the basalt interior

calculated effect of vesicles on the thermal properties of cooling basaltic lava flows abstract this paper investigates the effects of porosity in the form of vesicles and bubbles on the transfer of heat within basaltic lava this study was undertaken to provide input for realistic cooling models of basaltic lava flows and to help explain some recent field measurements by jones 1992 1993 these field observations indicate that the surfaces of vesicular pahoehoe flows cool significantly more rapidly than that of dense flows it has been suggested that thermal radiation across vesicles is responsible for this enhanced cooling rate it is shown here that for vesicles in typical pahoehoe flows radiation across vesicles may enhance the effective thermal conductivity and thermal diffusivity but only at high temperatures t 800 c and high vesicularities 40 it is also found that convection of the gas phase within bubbles will not occur unless the cavities are larger than about 1 cm furthermore previous work has demonstrated that porosity greatly reduces the thermal conductivity and thermal inertia of cold lava it is shown here that this should also be true at high temperatures examining only radiation across vesicles severely understates the effect of porosity on the cooling of the surface of lava flows thermal inertia developed to describe diurnal surface temperature variations is the most appropriate thermal parameter in this case thermal inertia is a measure of how quickly surface temperature responds to heating or cooling with low thermal inertia materials responding more quickly it is shown here that porosity greatly reduces thermal inertia at all temperatures and that this provides a more general explanation for the field observation

distribution and formation of rock varnish in southern tunisia field observations chemical analysis electron and light microscopy and radiolabelling experiments provide information on the characteristics formation and distribution of fe and mn rock varnishes in southern tunisia unstable rocks are not surface coated but when broken they commonly reveal internal microbial solution fronts stable rocks are coated in fe and more rarely mn rock varnishes radiolabelling indicates the presence of many respiring microbes on both fe and mn varnishes microscopy shows fungi and bacteria both on the fe varnishes and within the rock only rare microcolonial fungi occur on mn varnishes suggesting that the microbes are within or beneath the varnish the abundance of microorganisms supports a biogenic origin for rock varnishes different microbial communities appear to be involved in fe and mn varnish formation microbes appear to live beneath the surface of unstable rocks but coat stable rocks which cannot be penetrated apparently to avoid u v light and desiccation this explains the concentration of elements that form u v opaque minerals and clays the origin of these elements is external to the substrate these results suggest that rock varnish dating and paleoenvironmental techniques can be applied in southern tunisia

recovery of spectral emissivity from thermal infrared multispectral scanner imagery acquired over a mountainous terrain a case study from mount etna sicily the estimation of ground radiance and emissivity from thermal infrared multispectral scanner tims data is strongly dependent on the atmospheric correction applied to these data since such corrections are a function of the atmospheric path between the sensor and ground correction techniques that do not consider the topographic variations within a scene can introduce appreciable error in the estimation of the atmosphere effects in this paper we describe the development and application of a variable elevation atmospheric correction procedure our objective was to incorporate changes in target altitude into a general atmosphere correction strategy this procedure was tested on a tims data set acquired over mt etna italy in july 1986 the methodology adopted in this study is based on the use of the lowtran radiative transfer code and a digital elevation model dem registered to the image data the image data are divided into a series of layers based on elevation and a separate atmosphere correction is applied to each layer maps of emissivity estimates derived with the variable elevation approach were compared with geologic maps of the etna flow fields prior to the variable elevation correction the emissivity spectra of long lava flows appeared to vary with elevation following the variable elevation correction many of these spectral artifacts were removed from the emissivity maps in addition the variable elevation correction increased our ability to discriminate individual lava flows

combined use of visible reflected infrared and thermal infrared images for mapping hawaiian lava flows the weathering of hawaiian basalts is accompanied by chemical and physical changes of the surfaces these changes have been mapped using remote sensing data from the visible and reflected infrared and thermal infrared wavelength regions they are related to the physical breakdown of surface chill coats the development and erosion of silica coatings the oxidation of mafic minerals and the development of vegetation cover these effects show systematic behavior with age and can be mapped using the image data and related to relative ages of pahoehoe and aa flows the thermal data are sensitive to silica rind development and fine structure of the scene the reflectance data show the degree of oxidation and differentiate vegetation from aa and cinders together data from the two wavelength regions show more than either separately the combined data potentially provide a powerful tool for mapping basalt flows in arid to semiarid volcanic environments

effects of surficial modification processes on thermal infrared signatures in the arid southwestern united states thermal infrared spectra from both laboratory and remote sensing instruments were used to distinguish different age lava flows with varying amounts of surficial modification at cima and lunar crater volcanic fields the modification processes affecting the lava flows cause spectral differences that can be seen in remotely sensed emittance spectra from the thermal infrared multispectral scanner important influences on the thermal infrared spectra include aeolian mantling vegetation lava flow roughness and rock varnish laboratory thermal infrared reflectance spectra of the subaerially exposed surfaces of 1 15 cm basalt fragments at cima volcanic field show a feature attributable to rock varnish on the younger flows 0 14 0 75 m y that is lacking on the older flows 0 8 m y this suggests that rock varnish is thinner on the older flows at cima volcanic field scanning electron microscope images and thin sections of the different age flows at cima volcanic field support the conclusion that rock varnish is thinner and may be eroding on the older flow surfaces

relative dating of hawaiian lava flows using multispectral thermal infrared images a new tool for geologic mapping of young volcanic terranes the weathering of hawaiian basalts in arid and semiarid environments is accompanied by change in their thermal infrared emittance spectra the spectral differences can be measured and mapped with multispectral imaging systems the differences appear to be related to the degree of development preservation and alteration of glassy crusts the oxidation of iron and the accretion of silica rich surface veneers because the measurements are quantitative and in image format they are useful for estimating relative ages in geologic mapping of lava flows in hawaii this technique is most diagnostic for distinguishing among sparsely vegetated flows less than 1 5 ka in age

ore detection and grade estimation in the sudbury mines using thermal infrared reflectance spectroscopy this pilot study investigated the usefulness of thermal infrared reflectance tir spectroscopy to estimate ore grade in an underground environment and to separate ore bearing samples from their host rocks work was carried out under laboratory conditions to test the initial concept all samples had naturally broken faces to mimic the situation in a freshly blasted underground opening a total of 26 samples including massive and disseminated ores were collected from eight mines around the sudbury basin in ontario rock surfaces were measured wet and dry to address environmental conditions encountered underground to separate barren rocks from ores and for ore grade estimation an important finding of this research is that in the region of 1319cm 1 most known silicate minerals converge to a common reflectance minima 1 5 but massive and disseminated sulfides have distinctly higher reflectance individual sulfide minerals chalcopyrite pyrrhotite pentlandite however do not reveal diagnostic fea

rock type identification in a simulated underground environment using second derivative thermal infrared reflectance spectra this study investigates the usefulness of thermal infrared reflectance spectroscopy tir to map rock faces in an underground environment a laboratory fourier transform infrared ftir spectrometer was used to measure reflectance spectra 500 5000 cm 1 of freshly broken rock surfaces a total of 37 samples covering 10 different rock types including barren silicate rocks and rocks with disseminated sulfides was collected from eight mines around the sudbury basin in ontario freshly broken rock surfaces were measured wet and dry to address environmentalconditionsencounteredunder ground spectral data were processed by the second derivative approach and the spectral angle mapper algorithm sam for rock type identification an average of 77 accuracy was achieved for all rock types the success of this effort implies that hyperspectral analysis using second derivative spectra is effective to remove the effect of liquid water local geometry and disseminated sulfides while preserving diagnostic rock spectral signatures between 700 and 1300 cm 1

thermal infrared spectral character of hawaiian basaltic glasses multispectral thermal infrared remote sensing of hawaiian basalts younger than a few hundred years old can be used to discriminate basalt lava flows that are difficult to map with visible and near infrared images laboratory thermal infrared reflectance spectra of the exposed surfaces of mauna loa and kilauea basalts show systematic changes with age fresh glass collected from active lava flows shows a broad reflectance feature between 8 and 12 m indicative of a strong degree of disorder after a few weeks of exposure to the environment the spectra of the top surfaces of samples begin to exhibit spectral features suggestive of ordering into silicate chainlike and sheetlike units with progressive aging features of apparent sheetlike structures become the preferred mode as soon as 3 years after emplacement a silica rich coating can begin to develop on the surfaces adding another spectral feature to the laboratory reflectance measurements the thermal infrared multispectral scanner tims with six channels between 8 and 12 m has been used to take advantage of these spectral differences in basalts to map flows in hawaii remote sensing instruments with increased spectral resolution in the thermal infrared would aid in further discrimination of basalts with more subtle differences in age quenching and weathering histories

bottom pressure distribution due to wave scattering near a submerged obstacle the dynamic pressure distribution on the bottom of a wave flume due to the interaction of water waves with a submerged structure is investigated experimentally and analytically for both first and second order gravity waves of finite amplitude the dynamic pressure excess is found to be very important even for incoming waves propagating in deep water conditions in this depth condition a high pressure zone thirty times larger than the dynamic pressure excess expected in the absence of the obstacle is found in its vicinity on the other hand a low pressure zone is observed in the vicinity of the submerged obstacle for incoming waves propagating in smaller depth conditions in any case pressure gradients remain important the second order disturbance is found to be larger than first order in deep water conditions for some specific conditions and locations this result is interpreted in terms of nonlinear coupling of first order components including local modes

measured effects of desert varnish on the mid infrared spectra of weathered rocks as an aid to tims imagery interpretation the thermal infrared spectral properties 7 12 mu m of natural rock surfaces from silver lake ca are discussed although the reflectance of weathered rocks is largely a function of the quartz content in rocks the presence of desert varnish clay coating on rocks reduces the reflectance and spectral contrast with features unique to the rock spectra persisting if varnish is thin thick varnish has a spectrum with a reflectance peak near 9 6 mu m due to clays and resembles the spectra of clay rich playa surfaces comparison of laboratory reflectance spectra for varnish and weathered rock samples with thermal infrared multispectral scanner tims emissivity spectra for silver lake suggests that tims signatures for felsic rocks are dominated by weathered rock and rock debris in contrast it is likely that varnish plays an important role in the tims signatures of mafic rocks

mapping the distribution of vesicular textures on silicic lavas using the thermal infrared multispectral scanner the thermal infrared multispectral scanner tims is a potentially powerful tool for mapping detailed chemical variations in silicic lava flows which in turn could expand knowledge of pre eruption compositional gradients and mixing processes in silicic magma bodies however thermal infrared image data may be greatly influenced by the range of vesicular textures which occur on silicic flows to investigate the effect of vesicularity on tims imagery independent of chemical variations we studied little glass mountain at the medicine lake volcano of northern california a large rhyolitic flow of uniform composition but textural heterogeneity the imagery was recalibrated so that the digital number values for a lake in the scene matched a calculated ideal spectrum for water tims spectra for the lava show useful differences in coarsely and finely vesicular pumice data particularly in tims bands 3 and 4 images generated by ratioing these bands accurately map out those areas known from field studies to be coarsely vesicular pumice these texture related emissivity variations are probably due to the larger vesicles being relatively deeper and separated by smaller septa leaving less smooth glass available to give the characteristic emission of the lava in studies of inaccessible lava flows as on mars areas of coarsely vesicular pumice must be identified and avoided before chemical variations can be interpreted remotely determined distributions of vesicular and glassy textures can also be related to the volatile contents and potential hazards associated with the emplacement of silicic lava flows on earth

first use of an airborne thermal infrared hyperspectral scanner for compositional mapping in may 1999 the airborne thermal infrared hyperspectral imaging system spatially enhanced broadband array spectrograph system sebass was flown over mormon mesa nv to provide the first test of such a system for geological mapping several types of carbonate deposits were identified using the 11 25 m band however massive calcrete outcrops exhibited weak spectral contrast which was confirmed by field and laboratory measurements because the weathered calcrete surface appeared relatively smooth in hand specimen this weak spectral contrast was unexpected here we show that microscopic roughness not readily apparent to the eye has introduced both a cavity effect and volume scattering to reduce spectral contrast the macroroughness of crevices and cobbles may also have a significant cavity effect the diminished spectral contrast is important because it places higher signal to noise ratio snr requirements for spectroscopic detection and identification this effect should be factored into instrumentation planning and interpretations especially interpretations without benefit of ground truth sebass had the required high snr and spectral resolution to allow us to demonstrate for the first time the ability of an airborne hyperspectral thermal infrared scanner to detect and identify spectrally subtle materials

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

analysis of terrestrial and martian volcanic compositions using thermal emission spectroscopy 1 determination of mineralogy chemistry and classification strategies we have examined and applied existing classification schemes for volcanic rocks and developed new schemes using thermal emission spectra of terrestrial volcanic rocks laboratory thermal infrared spectra 5 25 m at 2 cm 1 spectral sampling deconvolved modal mineralogies and derived mineral and bulk rock chemistries were used to distinguish basalt basaltic andesite andesite and dacite modal mineralogies derived from linear deconvolution of terrestrial volcanic rocks were compared to modes measured by an electron microprobe phase mapping technique to determine the accuracy of linear deconvolution in modeling specific mineral abundances one standard deviations of the absolute differences between modeled and measured mineral abundances range from 2 4 to 12 2 vol with an average standard deviation of 4 8 vol being in agreement with average uncertainties calculated in previous studies weighted average compositions of feldspars in the deconvolution generally overlap the measured ranges of plagioclase compositions and the presence of low calcium and high calcium pyroxenes was correctly identified bulk chemistries of volcanic rocks were derived with a relatively high degree of accuracy 1 standard deviations ranging from 0 4 to 2 6 vol by combining the compositions of spectrally modeled phases in proportion to their relative abundances in a particular sample these data were collectively used to examine existing and develop new volcanic rock classification schemes however no single classification scheme was effective in accurately classifying all samples multiple steps of classification were required to distinguish volcanic rocks reflecting the mineralogic diversity and continuum of compositions that exists in volcanic rock types in a companion paper hamilton et al this issue these schemes are applied to the classification of martian surface compositions

aster observations of thermal anomalies preceding the april 2003 eruption of chikurachki volcano kurile islands russia abstract chikurachki volcano northern kurile islands chain paramushir island 50 20 n 155 27 e elevation 1816 m stratovolcano has been in a state of unrest for over twenty years its most recent eruption that began in april 2003 was preceded by an eruption between january and may 2002 thermal infrared images from the japanese united states advanced spaceborne thermal emission and reflection radiometer aster 5 tir channels 8 12 m 90 m pixel noise equivalent delta temperature ne t 0 1 0 3 k onboard the u s national aeronautics and space administration s terra polar orbiting spacecraft of a snow covered chikurachki volcano taken in january 2003 show muted evidence of thermal activity aster thermal infrared tir images from february 2003 however indicate warmer areas within the summit crater average whole pixel temperatures of adjacent summit slopes are in the range of 250 252 k while many summit crater whole pixel temperatures are 2 6 k greater a two component planck solution for the warmer pixels yields a solution of 275 277 k for 10 15 of the chikurachki summit crater and 285 295 k for 25 35 of a prominent hotspot on its flank an interpretation of this enhanced pre eruption heat flow is the presence of surface melt water the detection in aster data of such subtle precursory heat flow enhancement even retrospectively raises important issues for remote monitoring of dormant snow capped volcanoes especially those that threaten nearby populations like mt rainier

origin development and chemistry of silica alumina rock coatings from the semi arid regions of the island of hawaii abstract exposed rock surfaces in the semi arid regions of the island of hawaii are characterized by an x ray amorphous silica alumina surface coating ranging in thickness from a few to several hundred micrometers these coatings are composed of clear to translucent white lamellae of amorphous silica with a minor component of some amorphous aluminum phase and in some cases interlayered fine grained clastic material the coatings are derived from exogenous material both the amorphous silica alumina component and the clastic component of the coating are derived locally description of the chemical composition mineralogy and the morphology of the coating along with an evaluation of possible sources enables formulation of a model which describes their development because the composition and mineralogy of the coatings is dissimilar from all likely source materials direct incorporation of the source material could not account for the coating instead fine grained clastic material locally derived from the soil is blown onto the rock surface during a later non violent wetting event such as fog or dew some of this material goes into solution as this solution is evaporated poorly ordered mineral phases precipitate onto the rock surface forming the coating some of the clastic material is incorporated into the coating during the precipitation late stage precipitates are removed during later more dynamic wetting events such as a heavy rainfall which wash across the rock surface