note that all figures and tables link to the full power point presentation!!
Poster text and Power Point
presentation from Cities on Volcanoes III conference in Hilo, Hawaii,
the Soufriére Hills Dome: Fusion of Thermal Infrared Spaceborne
Data with a Multi-parameter Database
Kuhn and Michael S. Ramsey
Image Visualization and Infrared Spectroscopy (IVIS) Laboratory (http://ivis.eps.pitt.edu)
Department of Geology and Planetary Science University of Pittsburgh,
Pittsburgh, PA 15260, USA
Emplacement processes of the Soufriére Hills dome (Montserrat)
can be discerned using thermal infrared (TIR) wavelengths, which are sensitive
to changes in temperature flux and emissivity variations over time. With
the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER),
one cloud-free image is captured every three months on average, with increased
frequency in 2002, when the volcano was a high priority target. Montserrat
Volcano Observatory weekly reports from 1999 to present (available online)
were also ingested into a multi-parameter, searchable database. These
data, which detail specific volcanic activity, were compared against the
ASTER data. The database fields include SO2 flux,
GOES-derived radiance measurements, description of dome growth and collapse,
and intensities of pyroclastic flows, rockfalls, fumarolic activity, and
seismic activity. This database provides a unique cross-reference for
the interpretation of the spaceborne data, as well as highlighting observable
trends in each of the volcanic activity types. We hope to apply this methodology
in the prediction and monitoring efforts of active dome hazards elsewhere.
Soufriére Hills (FIGURE 1), an
active andesitic dome, has undergone three different eruptive phases since
reactivation in 1992. The first began in 1995 and continued through 1998,
with cycles of growth and collapse. From early 1998 to late 1999, the
duration of the second phase, is characterized by no extrusion, but dome
collapse and small explosions. The third phase, from late 1999 to present,
shows renewed extrusion, with two major collapses [Montserrat Volcano
Observatory, 2002]. An understanding of extrusion behavior, particularly
an adequate degassing of volatiles, can provide information on the triggers
of explosivity. Presuming that thermal emission spectra combine linearly
in thermal infrared wavelengths, aerial percentages of two end-members
(obsidian and vesicles) can be estimated using a linear spectral deconvolution
technique [Ramsey and Fink, 1999]. Variations in surface texture between
the two end-members specifically provide insight of emplacement time or
extrusion rate, volatile content, and internal structure of the dome.
ASTER is the first high resolution, multi-spectral (FIGURE
4) spaceborne instrument capable of discerning these features. ASTER
does not, however, provide any information about the eruptive phase of
the volcano. The GOES satellite, imaging approx. every 15 minutes, does
provide information on the eruptive phase [Harris et al, 2001] if tracked
long term (at least a week). Further, a multi-parameter database offers
a complementary set of data unobtainable from spaceborne satellites. The
fusion of these two datasets with ASTER imagery provide a foundation for
analysis of surface texture.
Data Sets and Methods
• Six Level 2 05 (emissivity)
and 06 (kinetic temperature) ASTER image products were chosen based on
the presence of an anomaly and relative absence of clouds (FIGURE
• For each image, the emissivity spectra were
unmixed against the endmembers of obsidian and blackbody for the four
hottest pixels, and plotted in FIGURE 4.
• Level 2 (atmospherically corrected) and Level 1 B (non-atmospherically
corrected) images were then resampled to 4x4 km pixel sizes to mimic GOES
resolution (FIGURE 3). Temperatures of
the pixel that includes the dome were plotted in FIGURE
6 for all three data sets. GOES band 5 (11.5-12.5 µm) temperatures
span one hour prior and hour of ASTER image capture.
• The online Montserrat Volcano Observatory (MVO) weekly reports
from December of 1999 to April of 2002 were converted into a database
to serve as a look-up table for ASTER imagery.
• Numerical data were graphed with a smoothing curve, explosive
events, and ASTER capture to illustrate increasing or decreasing trends
in activity (FIGURE 7).
• Statistical tests were conducted on numerical and categorical
data based upon previous correlations determined by other researchers
on smaller temporal scales. The following positive correlations were chosen
for statistical analyses:
1. Gas venting and rockfall [Luckett
et al, 2002]
2. Rockfall and long-period events [Cole et al, 1998]
3. Hybrid events should precede dome collapse [Neuberg et al, 1998]
4. Hybrid events should precede major explosions [Neuberg et al, 1998]
5. Long-period events should precede major explosions [Miller et al, 1998]
6. Hybrid events should precede rockfall [White et al, 1998]
7. Hybrid events linked to violent degassing [White et al, 1998]
8. Long-period events should precede and follow large hybrid events [White
et al, 1998]
9. Collapses preceded by long-period and hybrid events [Neuberg et al,
10. Volcano-tectonic events should be low during dome growth [Miller et
Results and Conclusions
Linear spectral deconvolution results
are reported in Table 1.The total percentage
of obsidian and blackbody should equal 100, however, for most pixels containing
an anomaly, this is not the case. Anomalous pixels for the April 13th,
2002 image are favorable, along with pixels at or near background temperature.
Petrographic analysis demonstrates a 5-15% glass content for samples thought
to have resided in the dome for a significant amount of time, and 25-30%
for samples collected after explosive eruptions [Sparks et al, 2000].The
week including the April 13th, 2002 capture shows a higher number of rockfalls
and mild dome growth, but the imagery suggests relatively uniform heat
distribution over each pixel and a 27-64% glass content. Possibly a third
endmember, i.e. andesite, should be considered. Another hypothesis to
explain the results (Figure 5) suggests
a pixel with a smaller percentage of elevated temperature results in a
radiance curve derived from two blackbody curves, one for the cooler temperature
and one for the hot temperature [Dozier, 1981]. Further investigation
using sub-pixel analysis is required in order to account for anomalous
The temperatures from the ASTER instrument
versus GOES are somewhat inconclusive. ASTER temperatures differ from
1.6 ºC to 13.7 ºC and do not plot consistently higher or lower
than the GOES temperatures. To further investigate temperature inconsistencies
between ASTER and GOES, more work should be performed in other areas,
such as Bezymianny and Unzen.
Statistical results show that some
variables correlate on a weekly temporal scale, while others do not. Results
for correlation #1 based on regression and ANOVA tests reveal a best line
of fit as y=353.986 + 0.164x, a p-value of 0.002, and an f-value of 10.375.
No correlation was found with #4, except when hybrid activity was separated
into two groups, below 25 and 26 and above. Fisher’s exact test
shows a p-value of 0.008 between explosive behavior and a high number
of hybrid events. Correlation #6 shows that the average number of rockfalls
is fewer with high values of hybrid events with a t-value of -3.2 and
a two-tailed p-value of 0.002. All other variables show no correlations.
Cole et al., Pyroclastic flows generated by gravitational instability
of the 1996-97 lava dome of Soufriére Hills Volcano, Montserrat.
Geophys. Res. Lett., 25, pp. 3425-3428, 1998
Dozier, J., A method for satellite
identification of surface temperature fields of sub-pixel resolution.
Remote Sens Environ, 11, pp. 221-229, 1981
Druitt, T. H., and Kokelaar, B. P.
(eds). The Eruption of Soufriére Hills Volcano, from 1995 to 1999.
Geological Society, London, Memoirs, 21, 595-602, 2002
Harris, A.J.L., Pilger, E., Flynn,
L.P., Web-Based Hot Spot Monitoring using GOES: What it is and How it
Works. Advances in Environmental Monitoring and Modeling, 1, pp. 3-31,
Miller et al., Seismicity associated
with dome growth and collapse at the Soufriére Hills Volcano, Montserrat.
Geophys. Res. Lett., 25, pp. 3401-3404, 1998
Montserrat Volcano Observatory, http://www.mvo.ms/
Neuberg et al., Results from the
broadband seismic network on Montserrat. Geophys. Res. Lett., 25, pp.
Neuberg et al., Models of Tremor
and low-frequency earthquake swarms on Montserrat. J. Volcanol. Geotherm.
Res., 101, pp. 83-104, 2000
Ramsey, MS and Fink, JH. Estimating
silicic lava vesicularity with thermal remote sensing: a new technique
for volcanic mapping and monitoring. Bull Volcanol., 61:32-39, 1999
Sparks et al., Control on the emplacement
of the andesite lava dome of the Soufriére Hills volcano, Montserrat
by degassing-induced crystallization. Terra Nova, 12, p. 14, 2000
White et al., Observations of hybrid
seismic events at Soufriére Hills Volcano, Montserrat: July 1995
to September 1996. Geophys. Res. Lett., 25, pp. 3657-3660, 1998