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| Titel |
What is controlling spectral reflectance of lava flows? First results of a field spectrometric survey of volcanic surfaces on Tenerife Island |
| VerfasserIn |
Long Li, Matthieu Kervyn, Carmen Solana, Frank Canters |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250089188
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| Publikation (Nr.) |
 EGU/EGU2014-3383.pdf |
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| Zusammenfassung |
| Space-based remote sensing techniques have demonstrated their great value in volcanic
studies thanks to their synoptic spatial coverage and the repeated acquisitions. On satellite
images, volcanic surfaces display a wide range of colors, and therefore contrasted reflectance
spectra. Understanding the factors controlling the spectral reflectance of volcanic materials at
different wavelength is essential to mapping volcanic areas. Detailed investigation into
spectra of volcanic materials are, however, restricted due to the trade-off between spatial and
spectral resolution of space-based sensors, such as Hyperion imagery that allows resolving
220 spectral bands ranging from 400 to 2500 nm with a spatial resolution of 30 meters.
In order to better understand reflectance of volcanic materials, especially lava, a
field campaign was launched in Tenerife Island, Spain in November 2013 with an
ASD FieldSpec 3 to document the reflectance spectra of historical mafic lava flow
surfaces.
20 specific lava and lapilli surfaces, with contrasted age, surface roughness, weathering
condition and vegetation coverage were characterized, using a systematic recording method
documenting the spectra’s variability within a 15x15 m2 area. Results show that all the
volcanic materials have great differences in spectral reflectance. Among them, lava’s
reflectance is low but still slightly higher than that of lapilli. Comparison of rough
and smooth lava surfaces on the same lava flow suggests that roughness tends to
increase the reflectance of lava surfaces. Also, vegetation and lichen alter lava’s
reflectance in some spectral regions, especially through a rise in the near infrared part of
the spectrum. It is therefore suggested that reflectance spectra of lava evolve over
time due to weathering processes, such as chemical alteration and growth of lichen
and moss. In addition, it is possible to compare field measurements with spectra
derived from Hyperion imagery, resulting in a strong match for some surfaces.
In order to increase the comparability of field and image spectra, geometric and
atmospheric correction should be improved, and field measurements should be
optimized by selecting volcanic surfaces to be measured in larger, more homogeneous
areas.
The field work that was done in Tenerife Island might provide an insight into spectral
properties and evolution of lava flows in other planets. |
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