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Lava flow superposition: The reactivation of flow units in compound ’a’a flows
Author(s)
Language
English
Obiettivo Specifico
Status
Published
JCR Journal
JCR Journal
Peer review journal
Yes
Title of the book
Issue/vol(year)
4/194 (2010)
Publisher
Elsevier
Issued date
May 10, 2010
Abstract
Basaltic 'a'ā lava flows often demonstrate compound morphology, consisting of many juxtaposed and
superposed flow units. Following observations made during the 2001 eruption of Mt. Etna, Sicily, we
examine the processes that can result from the superposition of flow units, when the underlying units are
sufficiently young to have immature crusts and deformable cores. During this eruption, we observed that
the emplacement of new surface flow units may reactivate older, underlying units by squeezing the still-hot
flow core away from the site of loading. Here, we illustrate three different styles of reactivation that depend
on the time elapsed between the emplacement of the two flow units, hence the rheological contrast between
them. For relatively long time intervals (2 to 15 days), and consequently significant rheological contrasts,
superposition can pressurise the underlying flow unit, leading to crustal rupture and the subsequent
extrusion of a small volume of high yield strength lava. Following shorter intervals (1 to 2 days), the
increased pressure caused by superposition can result in renewed, slow advance of the underlying
immature flow unit front. On timescales of < 1 day, where there is little rheological contrast between the
two units, the thin intervening crust can be disrupted during superposition, allowing mixing of the flow
cores, large-scale reactivation of both units, and widespread channel drainage. This mechanism may
explain the presence of drained channels in flows that are known to have been cooling-limited, contrary to
the usual interpretation of drainage as an indicator of volume-limited behaviour. Because the
remobilisation of previously stagnant lava can occur swiftly and unexpectedly, it may pose a significant
hazard during the emplacement of compound flows. Constant monitoring of flow development to identify
areas where superposition is occurring is therefore recommended, as this may allow potentially hazardous
rapid drainage events to be forecast. Reactivation processes should also be borne in mind when
reconstructing the emplacement of old lava flow fields, as failure to recognise their effects may result in the
misinterpretation of features such as drained channels.
superposed flow units. Following observations made during the 2001 eruption of Mt. Etna, Sicily, we
examine the processes that can result from the superposition of flow units, when the underlying units are
sufficiently young to have immature crusts and deformable cores. During this eruption, we observed that
the emplacement of new surface flow units may reactivate older, underlying units by squeezing the still-hot
flow core away from the site of loading. Here, we illustrate three different styles of reactivation that depend
on the time elapsed between the emplacement of the two flow units, hence the rheological contrast between
them. For relatively long time intervals (2 to 15 days), and consequently significant rheological contrasts,
superposition can pressurise the underlying flow unit, leading to crustal rupture and the subsequent
extrusion of a small volume of high yield strength lava. Following shorter intervals (1 to 2 days), the
increased pressure caused by superposition can result in renewed, slow advance of the underlying
immature flow unit front. On timescales of < 1 day, where there is little rheological contrast between the
two units, the thin intervening crust can be disrupted during superposition, allowing mixing of the flow
cores, large-scale reactivation of both units, and widespread channel drainage. This mechanism may
explain the presence of drained channels in flows that are known to have been cooling-limited, contrary to
the usual interpretation of drainage as an indicator of volume-limited behaviour. Because the
remobilisation of previously stagnant lava can occur swiftly and unexpectedly, it may pose a significant
hazard during the emplacement of compound flows. Constant monitoring of flow development to identify
areas where superposition is occurring is therefore recommended, as this may allow potentially hazardous
rapid drainage events to be forecast. Reactivation processes should also be borne in mind when
reconstructing the emplacement of old lava flow fields, as failure to recognise their effects may result in the
misinterpretation of features such as drained channels.
Sponsors
The work was funded by NERC studentship NER/S/A2005/13681 and
grant NE/F018010/1.
grant NE/F018010/1.
References
Applegarth, L.J., Pinkerton, H., James, M.R., Calvari, S., 2010. Morphological complexities and hazards:
during the emplacement of channel-fed 'a'ā lava flow fields: a study of the 2001 lower flow field on
Etna. Bull. Volcanol. doi: 10.1007//s00445-010-0351-1.
Behncke, B., Neri, M., 2003. The July-August 2001 eruption of Mt. Etna (Sicily). Bull. Volcanol. 65, 461-
476.
Borgia, A., Linneman, S., Spencer, D., Morales, L.D., Andre, J.B., 1983. Dynamics of lava flow fronts,
Arenal-volcano, Costa-Rica. J. Volcanol. Geotherm. Res. 19, 303-329.
Calvari, S., Pinkerton, H., 1998. Formation of lava tubes and extensive flow field during the 1991-1993
eruption of Mount Etna. J. Geophys. Res. 103, 27291-27301.Calvari, S., Pinkerton, H., 1999. Lava tube morphology on Etna and evidence for lava flow emplacement
mechanisms. J. Volcanol. Geotherm. Res. 90, 263-280.
Calvari, S., INGV Catania staff, 2001. Multidisciplinary approach yields insight into Mt. Etna 2001
eruption. EOS Trans. AGU. 82, 653-656.
Calvari, S., Neri, M., Pinkerton, H., 2003. Effusion rate estimations during the 1999 summit eruption on
Mount Etna, and growth of two distinct lava flow fields. J. Volcanol. Geotherm. Res. 119, 107-123.
Cashman, K., Pinkerton, H., and Stephenson, J., 1998. Introduction to special section: Long lava flows. J.
Geophys. Res. 103, 27281-27289.
Coltelli, M., Proietti, C., Branca, S., Marsella, M., Andronico, D., Lodato, L., 2007. Analysis of the 2001
lava flow eruption of Mt. Etna from three-dimensional mapping. J. Geophys. Res. 112, F02029.
Duncan, A.M., Guest, J.E., Stofan, E.R., Anderson, S.W., Pinkerton, H., Calvari, S., 2004. Development of
tumuli in the medial portion of the 1983 'a'ā flow-field, Mount Etna, Sicily. J. Volcanol. Geotherm. Res.
132, 173-187.Favalli, M., Harris, A.J.L., Fornaciai, A., Pareschi, M.T., Mazzarini, F., 2010 The distal segment of Etna’s
2001 basaltic lava channel. Bull. Volcanol. 72, 119-127. doi: 10.1007/s00445-009-0300-z.
Fink, J.H., Griffiths, R.W., 1990. Radial spreading of viscous gravity currents with solidifying crust. J.
Fluid Mech. 221, 485-509.
Fink, J.H., Griffiths, R.W., 1992. A laboratory analogue study of the surface-morphology of lava flows
extruded from point and line sources. J. Volcanol. Geotherm. Res. 54, 19-32.
Guest, J.E., Kilburn, C.R.J., Pinkerton, H., Duncan, A.M., 1987. The evolution of lava flow-fields:
observations of the 1981 and 1983 eruptions of Mount Etna, Sicily. Bull. Volcanol. 49, 527-540.
Hon, K., Kauahikaua, J., Denlinger, R., Mackay, K., 1994. Emplacement and inflation of pāhoehoe sheet
flows- observations and measurements of active lava flows on Kīlauea volcano, Hawai‘i. Geol. Soc.
Am. Bull. 106, 351-370.
Hulme, G., 1974. The interpretation of lava flow morphology. Geophys. J. R. Astr. Soc. 39, 361-383.
Istituto Nazionale di Geofisica e Vulcanologia (Catania) syn-eruption reports:
http://www.ct.ingv.it/Etna2001/Main.htm.
Jeffreys, H., 1925. The flow of water in an inclined channel of rectangular section. Phil. Mag. 64, 794-807.
Kilburn, C.R.J., Lopes, R.M.C., 1988. The growth of 'a'ā lava flow-fields on Mount Etna, Sicily. J.
Geophys. Res. 93, 14759-14772.
Kilburn, C.R.J., Lopes, R.M.C., 1991. General patterns of flow field growth- 'a'ā and blocky lavas. J.
Geophys. Res. 96, 19721-19732.
Kilburn, C.R.J., Guest, J.E. 1993. 'A'ā lavas of Mount Etna, Sicily. In Kilburn, C.R.J. Luongo, G. (Eds.)
Active lavas: monitoring and modelling. UCL Press, London, pp. 73-106.Krauskopf, K.B., 1948. Lava movement at Parícutin volcano, Mexico. Geol. Soc. Am. Bull. 59, 1267-
1283.
Luhr, J.F., Simkin, T., 1993. Parícutin, the volcano born in a Mexican cornfield. Geoscience Press,
Phoenix, Arizona, 427 pp.
Mattox, T.N., Heliker, C., Kauahikaua, J., Hon, K., 1993. Development of the 1990 Kalapana flow-field,
Kīlauea volcano, Hawai‘i. Bull. Volcanol. 55, 407-413.
Peterson, D.W., Swanson, D.A., 1974. Observed formation of lava tubes. Stud. Speleol. 2, 209-222.
Pinkerton, H., Sparks, R. S. J., 1976. 1975 sub-terminal lavas, Mount Etna- case history of formation of a
compound lava field. J. Volcanol. Geotherm. Res. 151, 532-534.
Pinkerton, H., Wilson, L., 1994. Factors controlling the lengths of channel-fed lava flows. Bull. Volcanol.
56, 108-120.
Polacci, M., Papale, P., 1999. The development of compound lava fields at Mount Etna. Phys. Chem.
Earth. 24, 949-952.
Rowland, S.K., Walker, G.P.L., 1987. Toothpaste lava: Characteristics and origin of a lava structural type
transitional between pahoehoe and 'a'ā. Bull. Volcanol. 49, 631-641.
Walker, G.P.L., 1967. Thickness and viscosity of Etnaean lavas. Nature. 213, 484-485.
Walker, G.P.L., 1971. Compound and simple lava flows and flood basalts. Bull. Volcanol. 35, 579-590.
during the emplacement of channel-fed 'a'ā lava flow fields: a study of the 2001 lower flow field on
Etna. Bull. Volcanol. doi: 10.1007//s00445-010-0351-1.
Behncke, B., Neri, M., 2003. The July-August 2001 eruption of Mt. Etna (Sicily). Bull. Volcanol. 65, 461-
476.
Borgia, A., Linneman, S., Spencer, D., Morales, L.D., Andre, J.B., 1983. Dynamics of lava flow fronts,
Arenal-volcano, Costa-Rica. J. Volcanol. Geotherm. Res. 19, 303-329.
Calvari, S., Pinkerton, H., 1998. Formation of lava tubes and extensive flow field during the 1991-1993
eruption of Mount Etna. J. Geophys. Res. 103, 27291-27301.Calvari, S., Pinkerton, H., 1999. Lava tube morphology on Etna and evidence for lava flow emplacement
mechanisms. J. Volcanol. Geotherm. Res. 90, 263-280.
Calvari, S., INGV Catania staff, 2001. Multidisciplinary approach yields insight into Mt. Etna 2001
eruption. EOS Trans. AGU. 82, 653-656.
Calvari, S., Neri, M., Pinkerton, H., 2003. Effusion rate estimations during the 1999 summit eruption on
Mount Etna, and growth of two distinct lava flow fields. J. Volcanol. Geotherm. Res. 119, 107-123.
Cashman, K., Pinkerton, H., and Stephenson, J., 1998. Introduction to special section: Long lava flows. J.
Geophys. Res. 103, 27281-27289.
Coltelli, M., Proietti, C., Branca, S., Marsella, M., Andronico, D., Lodato, L., 2007. Analysis of the 2001
lava flow eruption of Mt. Etna from three-dimensional mapping. J. Geophys. Res. 112, F02029.
Duncan, A.M., Guest, J.E., Stofan, E.R., Anderson, S.W., Pinkerton, H., Calvari, S., 2004. Development of
tumuli in the medial portion of the 1983 'a'ā flow-field, Mount Etna, Sicily. J. Volcanol. Geotherm. Res.
132, 173-187.Favalli, M., Harris, A.J.L., Fornaciai, A., Pareschi, M.T., Mazzarini, F., 2010 The distal segment of Etna’s
2001 basaltic lava channel. Bull. Volcanol. 72, 119-127. doi: 10.1007/s00445-009-0300-z.
Fink, J.H., Griffiths, R.W., 1990. Radial spreading of viscous gravity currents with solidifying crust. J.
Fluid Mech. 221, 485-509.
Fink, J.H., Griffiths, R.W., 1992. A laboratory analogue study of the surface-morphology of lava flows
extruded from point and line sources. J. Volcanol. Geotherm. Res. 54, 19-32.
Guest, J.E., Kilburn, C.R.J., Pinkerton, H., Duncan, A.M., 1987. The evolution of lava flow-fields:
observations of the 1981 and 1983 eruptions of Mount Etna, Sicily. Bull. Volcanol. 49, 527-540.
Hon, K., Kauahikaua, J., Denlinger, R., Mackay, K., 1994. Emplacement and inflation of pāhoehoe sheet
flows- observations and measurements of active lava flows on Kīlauea volcano, Hawai‘i. Geol. Soc.
Am. Bull. 106, 351-370.
Hulme, G., 1974. The interpretation of lava flow morphology. Geophys. J. R. Astr. Soc. 39, 361-383.
Istituto Nazionale di Geofisica e Vulcanologia (Catania) syn-eruption reports:
http://www.ct.ingv.it/Etna2001/Main.htm.
Jeffreys, H., 1925. The flow of water in an inclined channel of rectangular section. Phil. Mag. 64, 794-807.
Kilburn, C.R.J., Lopes, R.M.C., 1988. The growth of 'a'ā lava flow-fields on Mount Etna, Sicily. J.
Geophys. Res. 93, 14759-14772.
Kilburn, C.R.J., Lopes, R.M.C., 1991. General patterns of flow field growth- 'a'ā and blocky lavas. J.
Geophys. Res. 96, 19721-19732.
Kilburn, C.R.J., Guest, J.E. 1993. 'A'ā lavas of Mount Etna, Sicily. In Kilburn, C.R.J. Luongo, G. (Eds.)
Active lavas: monitoring and modelling. UCL Press, London, pp. 73-106.Krauskopf, K.B., 1948. Lava movement at Parícutin volcano, Mexico. Geol. Soc. Am. Bull. 59, 1267-
1283.
Luhr, J.F., Simkin, T., 1993. Parícutin, the volcano born in a Mexican cornfield. Geoscience Press,
Phoenix, Arizona, 427 pp.
Mattox, T.N., Heliker, C., Kauahikaua, J., Hon, K., 1993. Development of the 1990 Kalapana flow-field,
Kīlauea volcano, Hawai‘i. Bull. Volcanol. 55, 407-413.
Peterson, D.W., Swanson, D.A., 1974. Observed formation of lava tubes. Stud. Speleol. 2, 209-222.
Pinkerton, H., Sparks, R. S. J., 1976. 1975 sub-terminal lavas, Mount Etna- case history of formation of a
compound lava field. J. Volcanol. Geotherm. Res. 151, 532-534.
Pinkerton, H., Wilson, L., 1994. Factors controlling the lengths of channel-fed lava flows. Bull. Volcanol.
56, 108-120.
Polacci, M., Papale, P., 1999. The development of compound lava fields at Mount Etna. Phys. Chem.
Earth. 24, 949-952.
Rowland, S.K., Walker, G.P.L., 1987. Toothpaste lava: Characteristics and origin of a lava structural type
transitional between pahoehoe and 'a'ā. Bull. Volcanol. 49, 631-641.
Walker, G.P.L., 1967. Thickness and viscosity of Etnaean lavas. Nature. 213, 484-485.
Walker, G.P.L., 1971. Compound and simple lava flows and flood basalts. Bull. Volcanol. 35, 579-590.
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