Publication Date:
2017-04-04
Description:
Abstract
The simultaneous solution of the Planck equation (the so-called ‘‘dual-band’’ technique) for two shortwave infrared Landsat
Thematic Mapper (TM) bands allows an estimate of the fractional area of the hottest part of an active flow and the temperature
of the cooler crust. Here, the dual-band method has been applied to a time series of Mount Etna eruptions. The frequency
distribution of the fractional area of the hottest component reveals specific differences between summit and flank lava flows.
The shape of the density function shows a trend consistent with a Gaussian distribution and suggests a relationship between the
moments of the distribution and the emplacement environment. Because flow composition of Etnean lavas generally remains
constant during the duration of their emplacement, it appears that the shape of any particular frequency distribution is probably
related to fluid mechanical aspects of flow emplacement that affect flow velocity and flow heat loss and thus the rate of
formation of the surface crust. These factors include the influence of topographical features such as changes in slope gradient,
changes in volume effusion rate, and progressive downflow increases in bulk or effective viscosity. A form of the general
theoretical solution for the ‘dual-band’ system, which illustrates the relationship between radiance in TM bands 5 and 7,
corresponding to hot fractional area and crust temperature, is presented. Generally speaking, it appears that for a given flow at
any point in time, larger fractional areas of exposed hot material are correlated with higher temperatures and that, while the
overall shape of that distribution is common for the flows studied, its amplitude and slope reflect individual flow rheological
regimes.
Description:
Published
Description:
(15-34)
Description:
reserved
Keywords:
Landsat TM;
;
thermal structures;
;
Mount Etna
;
04. Solid Earth::04.08. Volcanology::04.08.01. Gases
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
Format:
2003775 bytes
Format:
application/pdf
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