Surface temperature and spectral measurements at Santiaguito lava dome, Guatemala

Abstract

[1] An infrared thermometer, spectroradiometer and digital video camera were used to observe and document shortterm evolution of surface brightness temperature and morphology at Santiaguito lava dome, Guatemala. The thermometer dataset shows 40 -70 minute-long cooling cycles, each defined by a cooling curve that is both initiated and terminated by rapid increases in temperature due to regular ash venting. The average cooling rate calculated for each cycle range from 0.9 to 1.6°C/min. We applied a twocomponent thermal mixture model to the spectroradiometer (0.4 -2.5 mm) dataset. The results suggest that the observed surface morphology changed from a cool (120-250°C) crust-dominated surface with high temperature fractures (>900°C) in the first segment of the measurement period to an isothermal surface at moderately high temperature (350 -500°C) during the second segment. We attribute the change in the thermal state of the surface to the physical rearrangement of the dome's surface during the most energetic of the ash eruptions.

Textural Insights Into the Evolving Lava Dome Cycles at Santiaguito Lava Dome, Guatemala

“…The early Santiaguito lavas were very similar to the 1902 eruption products (Rose, 1972b;Singer et al, 2011;Scott et al, 2013) and may represent a pocket of left-over dacite in the magma reservoir (e.g., Scott et al, 2013;Singer et al, 2013); thus we assume that they erupted at a temperature similar to the Santa Maria eruption of around 850 • C (Scaillet et al, 1998;Singer et al, 2013;Andrews, 2014). Over time as progressively more andesitic magma was erupted we expect that the temperature of the magma increased, to reach a maximum of 950 • C, as estimated by Sahetapy-Engel et al (2004), and supported by Scott et al (2013) based on amphibole geothermometry. Similarly, there have been <8% changes in crystal fractions and Scott et al (2012) hypothesized that crystallization may be limited at shallow depths due to a "final quench" where microlites stop nucleating and growing.…”

“…The three other domes are mostly inactive, except for mild gas emission, and are thus accessible for textural analysis. Evolution of the domes has been extensively described and documented (Sapper, 1926;Williams, 1932;Rose, 1969, 1970;Rose et al, 1970Rose et al, , 1976Rose, 1972bRose, , 1973aRose, ,b, 1987bSmithsonian Institution, 1980-present;Anderson et al, 1995;Andres and Rose, 1995;Harris et al, 2002Harris et al, , 2003Harris et al, , 2004Bluth and Rose, 2004;Sahetapy-Engel et al, 2004Forbes, 2010;Sanderson et al, 2010;Brill, 2011;Holland et al, 2011;Ebmeier et al, 2012) providing a first order basis for the detailed textural and morphological analysis of lava dome emplacement attempted herein. Extrusion cycles have been classified based on extrusion rate (Rose, 1973b;Harris et al, 2003), but as yet classification of lava types and how they fit into the eruption sequence has not been investigated.…”

An assessment of hydrothermal alteration in the Santiaguito lava dome complex, Guatemala: implications for dome collapse hazards

“…The summit structure and activity of the currently active Caliente dome is controlled by the slow upward movement of a stiffened plug of dacite in a central conduit leading to both extrusion of a lava flow as well as periodic ash-and-gas eruptions (Bluth and Rose 2004;Johnson et al 2004;Sahetapy-Engel et al 2004;Johnson et al 2008;Sahetapy-Engel et al Sahetapy-Engel and Harris 2008); the structure of the other lava domes has not been well studied. Sapper and Termer (1930a) made early observations of endogenous growth of the dome complex in the 1920s, but multiple dome units and lava flows have erupted since (Rose 1972b;Rose 1987b;Harris et al 2003Harris et al , 2004.…”

Early Analysis of Landsat-8 Thermal Infrared Sensor Imagery of Volcanic Activity

“…Although 320-350 K might initially appear a low temperature when viewing an active volcanic surface, the 10,000 m 2 pixels of the TIRS are likely to be heterogeneous and to view surfaces displaying a range of temperatures associated with both active (and relict) volcanism and also unaffected ground and vegetation. Additionally, the presence of a lava dome at the volcano [29] suggests that only a very small proportion of the surface (i.e., cracks in the chilled lava dome surface) will be of incandescent temperature [30][31][32]. As such, the overall temperature detected at the pixel scale (the pixel integrated temperature, or PIT) is likely to average out at significantly below incandescence and quite possibly at around 320-350 K. This is corroborated by Figure 3a, which simulates a range of volcanic-like surfaces consisting of a hot component (at varying temperature) and a cooler component (at 300 K), each of varying proportions, that would produce a PIT at the peak of detection for TIRS bands: 360 K [1], and also by Figure 3b which displays the range of PITs that the individual pixel detection components of the TIRS would detect on viewing a variety of configurations of simulated volcanic-like surfaces, again assuming two surface components: a hot component of varying temperature and a cooler component of 300 K. The detection capabilities of the thermal infrared bands to surfaces at ambient temperature does mean, however, that these ambient emissions must be removed from those of the brighter volcanic pixels to retrieve the purely anomalous radiant emissions attributable solely to volcanic activity.…”