150°C

1. Conduit thermal patterns as revealed by infrared imagery at Santiaguito, Guatemala Summit Crater Outer Annulus Santa Maria W I Rose, Lara Kapelanczyk, Adam Blankenbicker, Luke Bowman, Otoniel Matías, Rüdiger Escobar Wolf, John Lyons, Kyle Brill, José Luis Palma Inner Annulus Santiaguito Lava Dome Complex Caliente vent Hot Central Core Cool Inner Annulus Central Core Thermal IR images obtained with a FLIR device show a hot ring pattern which has been observed repeatedly at Santiaguito. The hot ring is sustained by weak vertical eruptions that occur every 15-200 minutes and preferentially heat the ring while slight slippage occurs along the conduit margin, extruding lava which feeds a lava flow descending one flank of the dome. Hot Outer Annulus discontinuity Temperature (°C) Hot Central Core 150°C Hot Central Core 100°C 100°C 150 °C Cool Inner Annulus 150 °C Caliente vent Cool Inner Annulus discontinuity Hot Outer Annulus discontinuity Hot Outer Annulus N N N N N W W W W E 100 m W W W W W E E E E E N S S S N N N S N S 0°C 0°C 0 °C -10°C W S S S S S 0 °C Profile Distance (m) E E E E Jan 12, 2008 Jan 16, 2005 Jan 12, 2008 July 2, 2008 Sahetapy-Engel & Harris 2008, Bull Volc Temperature profiles across the summit conduit at Caliente in 2005 (left) and 2008 (right). Note that 2005 conduit areas are 25% higher, maximum temperatures are 140 degrees higher and total heat flow is more than double. There is also a slight temperature decrease from January to June 2008, but this may be explained by wet and dry season effects. Jan 10, 2008 Jan 11, 2008 conduit Jan 9, 2008 Jan 10, 2008 Jan 11, 2008 Flow front rockfalls Thermal IR views of the active lava flow of Jan 2008. Heat loss from the flow surface is ~4 times more than the conduit alone. Santiaguito is a lava dome that has been continuously active since 1922. A new orthophoto geological map of Santiaguito (Escobar et al., this meeting) reveals the pattern of continued exogenous growth of the Caliente Vent region in the last decade, consisting mainly of thick flows to the S. Extrusion has been focused on the cylindrical 80 m diameter vent region which displays a thermal circular ring pattern of high temperatures on most observed occasions. This ring marks the alignment of ash vents which drive periodic (about every 0.2 to 2 hour) vertical thermal explosions. Extruded lava moves upward and down the side of the dome, usually to the south. In recent years systematic thermal observations from helicopter and ground sites have supplemented satellite data and DEMs to provide data to estimate extrusion rates. Santiaguito is a site of significant pyroclastic flows, dome collapses and lahars. It is hoped that frequent observations and eruption rate estimates will lead to improved hazard forecasts. Seen from the east, a lava flow extruded about a year ago still shows residual heat. Lava flow Jan 11, 2008 Above the conduit, lava flows downslope and may move in a variety of directions. This oblique view of the Caliente vent region centers on the conduit and green shading outlines the two most recent flow lobes of 2006-7 (eastward) and 2007-8 (westward). Telephoto of conduit from Santa María in 2007 (Jeff Johnson), during period when lava was flowing eastward from the conduit. This flow disrupted the symmetry of the ring, causing it to deform by flow. Compare with photos at top when flow was moving W. 2007-8 Summary Points: Santiaguito heat flow is about 42 MJ/s in 2008. This rate is equivalent to an extrusion rate of about 0.1 m3/s and is apparently decreasing. 2006-7 Acknowledgments: This research is supported by the US National Science Foundation through OISE and PIRE 0530109. Thermal imaging equipment purchased with NSF EAR 0732632. The US Peace Corps supports collaborative field work at Guatemalan volcanoes. Our Guatemalan partner organizations INSIVUMEH and CONRED work with us and provide logistical support. Steve Sahetapy-Engel provided data and advice. • References: • Ball M and H Pinkerton, 2006, Factors affecting the accuracy of thermal imaging cameras in volcanology, J Geophys Res 111, B 11203, doi: 10.1029/2005JB003829. • Barmin, A, O Melnik and RSJ Sparks, 2002, Periodic behavior in lava dome eruptions, EPSL 199: 173-184. • Bluth G J S and W I Rose, 2004, Observations of eruptive activity at Santiaguito volcano, Guatemala, J Volcanol Geoth Res 136: 297-302. • Durst, KS, W I Rose, R Escobar-Wolf, A Maclean and MR Sanchez, 2008, Erupted magma volume estimates at Santiaguito and Pacaya Volcanoes, Guatemala, using digital elevation models, Bulletin of Volcanology, in review. • Escobar Wolf, R P, O Matías Gomez and W I Rose, 2008, Geologic map of Santiaguito, Guatemala, unpublished map presented at IAVCEI, Reyjavik, August 2008. • Gonnermann HM and M Manga, 2003, Explosive volcanism may not be an inevitable consequence of magma fragmentation, Nature 426: 432-435. • Harris, A.J.L., Flynn, L.P., Matías, O. and Rose, W. I., 2002, The thermal stealth flows of Santiaguito: implications for the cooling and emplacement of dacitic block lava flows, Geol. Soc. Am. Bull., 114: 533-546. • Harris, A.J.L., W I Rose and Flynn, L.P., 2003, Temporal trends in Lava Dome extrusion at Santiaguito, 1922-2000, Bulletin of Volcanology 65: 77-89. • Harris, Andrew J. L., Luke P. Flynn, Otoniel Matías, William I. Rose and Julio Cornejo, 2004, The evolution of an active silicic lava flow field: an ETM+ perspective, J Volcanol Geoth Res 135: 147-168 • Johnson, J B, A J L Harris, S T M Sahetepy-Engel, R Wolf and W I Rose, 2004, Explosion dynamics of pyroclastic eruptions at Santiaguito Volcano, Geophys Res Lett 31: L 0066010. • Rodríguez, L.A., Watson, I.M., Rose, W.I., Branan, Y.K., Bluth, G.J.S., Chigna, G., Matías, O., Escobar, D., Carn, S.A. and Fischer, T., 2004, SO2 emissions to the atmosphere from active volcanoes in Guatemala and El Salvador, 1999-2002, Journal of Volcanology and Geothermal Research, 138 (3-4), pp. 345-364. • Sahetepy-Engel S T M and A J L Harris, 2008, Thermal structure and heat loss at the summit crater of an active lava dome, Bulletin of Volcanology DOI 10.1007/s00445-008-0204-3 • Sahetepy-Engel S T M, L P Flynn, A J L Harris, G J Bluth, W I Rose and O Matías, 2004, Surface temperature and spectral measurements at Santiaguito Lava Dome, Guatemala, Geophysical Res Lett 31: L19610 During the brief eruptions, points in the outer annulus of the conduit are heated by about 100 degrees by the rising gases and fine ash moving through the conduit edges. Overall the heat flow from the conduit increases by about 10% after each event.