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Emission spectra of the units shown in Figs. 3-4 together with an emissivity equal to one representing an ideal blackbody. Spectra shown are averages of at least ten samples to account for orientation and weathered surface effects. The large absorption band at 9.25 mm is diagnostic of glass and is caused by the stretching vibrations of silica tetrahedra. The blackbody and obsidian (OBS) served as end members for the deconvolution model, which estimated the percentage of vesicles in the pumice based on the fit of the end-member spectra. CVP coarsely vesicular pumice; FVP finely vesicular pumice
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Remote monitoring of active lava domes provides insights into the duration of continued lava extrusion and detection of potentially
associated explosive activity. On inactive flows, variations in surface texture ranging from dense glass to highly vesicular
pumice can be related to emplacement time, volatile content, and internal structure. Pumiceo...
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... conditions affected by the volatile content, emplace- ment time, and internal structure of the flow. Although factors such as vesicle size and the scattering physics of reflected solar energy may complicate remote sensing analyses, pumiceous textures produce significant varia- tions in thermal emission spectra that are clearly distin- guishable (Fig. ...
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... This alteration of the fundamental structural makeup of a mineral due to vitrification causes a broadening and widening of the absorption bands together with the loss of most small-scale fea- tures ( Nash and Salisbury 1991;Ramsey et al. 1993). Typically, glassy lavas will contain only two prominent features in the 7-to 25-mm wavelength region (Fig. 1). The first, a broad V-shaped absorption band spanning 8-12 mm, is attributed to the stretching vibrations of sil- ica tetrahedra and is detectable within the Earth's at- mospheric window (8-13 mm). The second dominant absorption band occurs from 20-25 mm, well outside that window, and is therefore unavailable for remote sensing ...
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... of the emitted energy's wavelength. Therefore, photons are free to interact with one or more cavity surfaces, undergoing multiple reflections before being absorbed. Because the reflected energy (R) is related to the emitted energy (ε ) such that Rp1- ε , any amount of added reflected energy will increase the emissivity at the absorption bands ( Fig. 1) and thus approximate an ideal (blackbody) radiator. A similar phenomenon is observed in emission studies of fine particle sizes, where emitted photons are able to inter- act with progressively more reflecting surfaces (Ramsey and Christensen 1998;Mustard and Hays 1997). If the photon path is convoluted and the number of reflec- tions ...
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... rived by way of the blackbody end member. Spectra of glassy flows throughout the western United States, Ha- wai'i, and Central America have been examined over the course of this investigation. The data set is remark- ably uniform, with variations in emission feature mor- phology of less than F5%. This justifies the use of the end-member spectra (Fig. 1) chosen for this study and should allow a common glass end member to be used for data of remote flows using ...
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... of 1993-1995. High-resolution laboratory spectra of each were acquired at the Arizona State Uni- versity Thermal Emission Spectrometer Laboratory ( Ruff et al. 1997). Data were taken from fresh and wea- thered surfaces as well as at several different sample orientations in order to quantify the magnitude of these effects. The spectra shown in Fig. 1 were derived from the 2-cm spot size of the spectrometer and were aver- aged to represent the many different vesicle orienta- tions present on the surface of the flow. The linear de- convolution model, originally developed to detect mi- neralogic variations (Ramsey and Fink 1994;Ramsey and Christensen 1998), was adapted for use as a ...
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... laboratory-derived spectra ( Fig. 1) were re- duced to the six-point TIMS spectral resolution. With the OBS and a blackbody serving as spectral end mem- bers, the model was utilized to produce a vesicle-per- centage image for the dome (Fig. 6). Average values from areas of known surface texture were extracted from this image and compared with the laboratory re- sults and ...
Citations
... Spectral mixing is also affected by sample porosity. Surface reflections occur in pore spaces, so increased porosity in fine particle samples can result in Earth and Space Science 10.1029/2023EA003439 photons interacting with multiple particles before exiting the surface, resulting in nonlinear mixing (Mustard & Hays, 1997;Ramsey & Fink, 1999;Salisbury & Eastes, 1985). ...
The glass phase in volcanic rocks presents a challenge to obtaining compositional data from visible and short‐wave‐infrared (VSWIR) and mid‐infrared (MIR) spectral data of remote surfaces due to its amorphous structure and variable composition. Nonetheless, glass is a common phase in volcanic materials because it forms via the rapid quench of magma and can constitute up to the entirety of a volcanic deposit. Use of partial least squares regression (PLS) to predict glass contents creates models that are insensitive to viewing geometry and sample conditions such as grain size and spectrally inactive compositional variables, enhancing the ability to detect glasses with remote sensing. PLS models are used here to predict crystallinity and oxide composition of samples from VSWIR and MIR spectral data using training spectra from natural volcanic rocks and geologically relevant synthetic samples. Three spectral resolutions of VSWIR and MIR spectra (1, 10, and 100 nm/band, and 1.9, 19, and 190 cm⁻¹/band, respectively) were tested to assess the effects of collection configuration on different spectrometers. PLS models trained on 1 nm and 1.9 cm⁻¹ data sets have the lowest uncertainties of glass modal abundance for VSWIR and MIR, respectively. MIR models predicting sample wt. % SiO2 and FeO, and VSWIR models of wt. % FeO provide accurate estimates (e.g., RMSE‐P of 3.4 wt. % FeO) at all spectral resolutions. Results are based on training data sets skewed to mafic compositions, which affects model accuracies.
... Various satellite-based remote sensing technologies, such as the advanced spaceborne thermal emission and reflectance radiometer (ASTER) and Landsat series datasets, have been instrumental in estimating silicic lava vesicularity, volcanic mapping, and monitoring activities [8][9][10][11] . Additionally, synthetic aperture radar (SAR) 12 and thermal infrared (TIR) imaging 2,13-15 have proven effective tools in detecting changes in the shape, size and temperature of volcanoes. ...
... The main diagnostic spectral features are evident in these spectra, even with the five spectral bands of the ASTER TIR sensor. (C) Furthermore, by utilizing the methods of Ramsey and Fink (1999), micron-scale roughness associated with the percentage of vesicles can be derived using a linear deconvolution approach of glass plus a featureless blackbody spectrum. (D) RMS errors are low overall, indicating a good spectral fit. ...
Understanding the composition, texture, and morphology of volcanic rocks that have erupted at the surface better constrains the eruption style and is vital to infer subsurface processes, the development of magma upon ascent, and the potential for future eruptions. The reflectance and emission spectroscopy of these rocks, collected from the near-infrared (NIR) through the thermal infrared (TIR) portion of the electromagnetic (EM) spectrum, provides the data necessary to retrieve composition, micron-scale surface roughness, and particle size. Remote imaging systems enable the analyses of active volcanoes in remote regions, where sample collection for laboratory analysis poses a significant challenge. Laboratory hyperspectral data of samples acquired at volcanic deposits are easily resampled to the spectral resolution of any infrared sensor and provide a means of estimating the composition of volcanoes and their products worldwide, as well as those on other planetary bodies such as the Moon and Mars. In this review paper, we provide an overview of the current use of infrared reflectance and emission spectroscopy as an analysis tool in volcanology, including ground-based imaging systems that acquire unprecedented detail and serve as testbeds for new orbital concepts. We also discuss the potential impact that future satellite missions will have on volcano science as spectral, spatial, and temporal resolutions improve.
... Bubbles can change the appearance of the lava in visible, infrared, or radar observations (Ondrusek et al. 1993;Ramsey and Fink 1999). Remote sensing of the vesicular textures preserved on a flow surface can thus provide an indication of otherwise unobserved eruptive conditions. ...
After its cataclysmic explosive eruptive activity on May 18, 1980, most of the output of Mount St. Helens (MSH) for the next six and a half years was quietly extruding lava, which built up one of the best documented and most instructive lava domes of the twentieth century. The unprecedented amount of data collected about the growth of the dome led to a profusion of new models and concepts. In this paper, we first describe some of the early mechanical models and then focus on three specific aspects of the emplacement of the MSH lava dome that were measurable in particularly great detail: the partitioning between exogenous and endogenous styles of growth; the distribution of vesicular textures and their relationship to volatile contents and eruptive conditions; and the presence of characteristic structural features like fractures, folds, and spines. Taken together, these three overlapping physical manifestations of magmatic behavior, evidence of which may be preserved in the geologic record or observed with remote sensing, can provide insights about whether a quietly extruding dome is likely to exhibit dangerous endogenic pyroclastic behavior.
... Further, the presence of a V-shaped transmittance peak around 890 cm -1 in the spectra of both samples indicates their similar bulk chemical composition, as shown in table 1. The occurrence of this V-shaped peak also speciBes the region of silicate stretching vibrations and is usually observed for the glass and other poorly crystalline materials (Ramsey and Fink 1999;Michalski et al. 2003;Hamilton et al. 2008). The vibration bands between *675 and 725 cm -1 correspond to symmetric stretching of silicate (Si-O-Al and Si-O-Si) structure. ...
The formation of Pele’s hairs and tears (PH and PT) is generally associated with fluid-charged rapid explosive basaltic volcanism on Earth’s surface. Their formation and relationship with eruption types have led to a sudden increase in theoretical and experimental studies in recent years. Unlike previous experimental setups, the present study successfully formed these volcanic structures using a simple experimental design. The viscosity of basaltic melt was lowered to <100 Pa·s at 1200°C under 1 atmospheric pressure using a novel cylinder-in-cylinder graphite sample chamber for the in-situ fluxing of excess fluids into the melt system. The abundance of vesicles in the basaltic melt observed in mesoscopic to sub-microscopic scales suggests the presence of fluid phase in excess, its decoupling and degassing. The dissolved gas species in the experimentally generated melt are confirmed by the Fourier transform infrared spectroscopic analyses. The PH and PT formed during the present study compare morphologically very well to their known natural and experimental counterparts, and are found to be compositionally similar. They display a small range of chemical variations and exhibit a good chemical homogeneity similar to their natural analogues.
... Holocene-age obsidian lavas in California and Oregon, USA (e.g., Fink, 1983;Fink and Anderson, 2017), are among the most comprehensively studied lavas worldwide; additional important late Pleistocene and Holocene examples exist in the Aeolian Islands (Italy), the Chilean Andes, Iceland, Japan, and New Zealand (e.g., Stevenson et al., 1994;Maeno and Taniguchi, 2006;Lara, 2009;Tuffen and Castro, 2009;Pallister et al., 2013;Tuffen et al., 2013;Bullock et al., 2018). Investigations of these lavas have yielded important insights into silicic lava emplacement mechanisms through detailed studies of (1) morphology (e.g., Fink, 1980a;Ramsey and Fink, 1999;Deardorff et al., 2019;Leggett et al., 2020), (2) lithology and structure (e.g., Manley and Fink, 1987;Smith and Houston, 1994;Smith, 2002), and (3) microstructure and petrofabrics (e.g., Castro et al., 2002;Cañón-Tapia and Castro, 2004;Rust et al., 2003;Manga et al., 2018). Observations and quantitative data provide inspiration and constraints for many informative numerical and analog simulations (e.g., Griffiths, 1992, 1998;Merle, 1998;Lescinsky and Merle, 2005;Farrell et al., 2018;Kenderes, 2021). ...
The scarcity of observed active extrusive rhyolitic lava flows has skewed research to extensively focus on prehistoric lavas for information about their eruptive and emplacement dynamics. The first ever witnessed silicic lava eruptive events, Chaitén (2008) and Cordón Caulle (2011–2012) in Chile, were illuminating to the volcanology community because they featured a range of emplacement processes (endogenous versus exogenous), movement limiting modes, and eruptive behaviors (explosive versus effusive) that were often regarded as acting independently throughout an eruptive event. In this study, we documented evidence of a continuum of brittle and brittle-ductile deformation and fracture-induced outgassing during the emplacement of the ~600-yr-old silicic lava from Obsidian Dome, California, USA. This study focused on mapping the textural-structural relationships of the upper surface of the lava onto high-resolution (<10 cm2/pixel) orthorectified color base maps. We found that the upper surface is characterized by small (<1 m) mode 1 tensile fractures that grew and initiated new cracks, which linked together to form larger tensile fractures (1–5 m), which in turn penetrated deeper into the lava. We recorded ornamentations on these fracture surfaces that allow snapshot views into the rheological and outgassing conditions during the lava’s effusion. The largest fractures developed during single, large fracture events in the final stages of the lava’s emplacement. Ornamentations preserved on the fractured surfaces record degassing and explosive fragmentation away from the vent throughout the lava’s emplacement, suggesting explosive activity was occurring during the effusive emplacement. Field-based cataloguing of the complexities of fracture surfaces provides qualitative constraints for the future mechanical modeling of effusive lavas.
... Specular reflectance can be related to the directed emission, as required by Kirchhoff's law, so the differences will be mainly in spectral contrast. Band shape and positions of the spectra will be comparable between emission and converted specular reflectance (Ramsey and Fink, 1999;Byrnes et al., 2007;Lee et al., 2010). ...
In order to provide spectral ground truth data for remote sensing applications, we have measured midinfrared spectra (2 to 18 micron) of three typical, well defined lithologies from the Chelyabinsk meteorite. These lithologies are classified as (a) moderately shocked, light lithology, (b) shock darkened lithology, and (c) impact melt lithology. Analyses were made from bulk material in four size fractions (0 to 25 micron, 25 to 63 micron, 63 to 125 micron, and 125 to 250 micron), and from additional thin sections. Characteristic infrared features in the powdered bulk material of the moderately shocked, light lithology, dominated by olivine, pyroxene and feldspathic glass, are a Christiansen feature (CF) between 8.5 and 8.8 micron; a transparency feature (TF) in the finest size fraction at about 13 micron, and strong reststrahlen bands (RB) at about 9.1 micron, 9.5 micron, 10.3 micron, 10.8 micron, 11.2 to 11.3 micron, 12 micron, and between 16 and 17 micron. The ranges of spectral features for the micro FTIR spots show a wider range than those obtained in diffuse reflectance, but are generally similar. With increasing influence of impact shock from pristine LL5 (or LL6) material (which have a low or moderate degree of shock) to the shock-darkened lithology and the impact melt lithology as endmembers, we observe the fading or disappearing of spectral features. Most prominent is the loss of a twin peak feature between 10.8 and 11.3 micron, which turns into a single peak. In addition, in the pure impact melt endmember lithology features at about 9.6 micron and about 9.1 micron are also lost. These losses are most likely correlated with decreasing amounts of crystal structure as the degree of shock melting increases.
... Although specular reflectance is not entirely relatable to the directed emission, as required by Kirchhoff's law, the differences will be mainly in spectral contrast, otherwise (e.g. band shape and positions) the data will be comparable (Ramsey and Fink, 1999;Byrnes et al, 2007;Lee et al., 2010). ...
This study is part of an effort to build a mid-infrared database (7-14micron) of spectra for MERTIS (Mercury Radiometer and Thermal Infrared Spectrometer), an instrument onboard of the ESA/JAXA BepiColombo space probe to be launched to Mercury in 2017. Mercury was exposed to abundant impacts throughout its history. This study of terrestrial impactites can provide estimates of the effects of shock metamorphism on the mid-infrared spectral properties of planetary materials. In this study, we focus on the Noerdlinger Ries crater in Southern Germany, a well preserved and easily accessible impact crater with abundant suevite impactites. Suevite and melt glass bulk samples from Otting and Aumuehle, as well as red suevite from Polsingen were characterized and their reflectance spectra in mid-infrared range obtained. In addition, in-situ mid-infrared spectra were made from glasses and matrix areas in thin sections. The results show similar, but distinguishable spectra for both bulk suevite and melt glass samples, as well as in-situ measurements. Impact melt glass from Aumuehle and Otting have spectra dominated by a Reststrahlen band at 9.3-9.6 micron. Bulk melt rock from Polsingen and bulk suevite and fine-grained matrix have their strongest band between 9.4 to 9.6 micron. There are also features between 8.5 and 9 micron, and 12.5 - 12.8 micron associated with crystalline phases. There is evidence of weathering products in the fine-grained matrix, such as smectites. Mercury endured many impacts with impactors of all sizes over its history. So spectral characteristics observed for impactites formed only in a single impact like in the Ries impact event can be expected to be very common on planetary bodies exposed to many more impacts in their past. We conclude that in mid-infrared remote sensing data the surface of Mercury can be expected to be dominated by features of amorphous materials.
... It has been proved that three main atmospheric endmembers can be identified and combined linearly to model Martian TIR spectra: atmospheric dust, water ice clouds and a blackbody . In addition, as far as the modeling of the surface contribution is concerned, several works (i.e., Feely & Christensen, 1999;Gillespie, 1992;Hamilton & Christensen, 2000;Ramsey & Christensen, 1998;Ramsey & Fink, 1999;Thomson and Salisbury, 1993) showed that it is possible to approximately model the TIR spectra of a mixed surface through a linear combination of the end-members spectra, where each end-member is weighted by its areal concentration. ...
Key knowledge about planetary composition can be recovered from the study of thermal infrared spectral range datasets. This range has a huge diagnostic potential because it contains diagnostic absorptions from a planetary surface and atmosphere. The main goal of this study is to process and interpret the dataset from the Thermal Infrared channel (TIRVIM) which is part of the Atmospheric Chemistry Suite of the ExoMars2016 Trace Gas Orbiter mission to find and characterize dust and water ice clouds in the atmosphere. The method employed here is based on the application of principal component analysis and target transformation techniques to extract the independent variable components present in the analyzed dataset. Spectral shapes of both atmospheric dust and water ice aerosols have been recovered from the analysis of TIRVIM data. The comparison between our results with those previously obtained on Thermal Emission Spectrometer (TES) data and with previous analysis on TIRVIM data, validates the methodology here applied, showing that it allows to correctly recover the atmospheric spectral endmembers present in the TIRVIM data. Moreover, comparison with atmospheric retrievals on PFS, TES and IRIS data, allowed us to assess the temporal stability and homogeneity of dust and water ice components in the Martian atmosphere over a time period of almost 50 years.
... Different surface types or morphologies also vary in their thermophysical properties, such as thermal inertia, and can be identified using TIR remote sensing (Ramsey and Fink, 1999;Price et al., 2016;Ramsey et al., 2016;Simurda et al., 2020). Thermal inertia is a physical material property that is related to the resistance to temperature change and is commonly derived by modeling observations of the diurnal temperature response of a surface Simurda et al., 2020). ...
... Data from TIR sensors are also sensitive to density (e.g., Eq. 1). Ramsey and Fink (1999) demonstrated this concept for volcanic deposits, using multi-band airborne TIR imagery to quantify the vesicularity of silicic lava flows. ...
The deposits from volcanic eruptions represent the record of activity at a volcano. Identification, classification, and interpretation of these deposits are crucial to the understanding of volcanic processes and assessing hazards. However, deposits often cover large areas and can be difficult or dangerous to access, making field mapping hazardous and time-consuming. Remote sensing techniques are often used to map and identify the deposits of volcanic eruptions, though these techniques present their own trade-offs in terms of image resolution, wavelength, and observation frequency. Here, we present a new approach for mapping and classifying volcanic deposits using a multi-sensor unoccupied aerial system (UAS) and demonstrate its application on lava and tephra deposits associated with the 2018 eruption of Sierra Negra volcano (Galápagos Archipelago, Ecuador). We surveyed the study area and collected visible and thermal infrared (TIR) images. We used structure-from-motion photogrammetry to create a digital elevation model (DEM) from the visual images and calculated the solar heating rate of the surface from temperature maps based on the TIR images. We find that the solar heating rate is highest for tephra deposits and lowest for ʻaʻā lava, with pāhoehoe lava having intermediate values. This is consistent with the solar heating rate correlating to the density and particle size of the surface. The solar heating rate for the lava flow also decreases with increasing distance from the vent, consistent with an increase in density as the lava degasses. We combined the surface roughness (calculated from the DEM) and the solar heating rate of the surface to remotely classify tephra deposits and different lava morphologies. We applied both supervised and unsupervised machine learning algorithms. A supervised classification method can replicate the manual classification while the unsupervised method can identify major surface units with no ground truth information. These methods allow for remote mapping and classification at high spatial resolution (< 1 m) of a variety of volcanic deposits, with potential for application to deposits from other processes (e.g., fluvial, glacial) and deposits on other planetary bodies.
