Lava tube morphology on Etna and evidence for lava flow emplacement mechanisms

Lava tubes play a pivotal role in the formation of many lava flow fields. A detailed examination of several compound
‘a‘a lava flow fields on Etna confirmed that a complex network of tubes forms at successively higher levels within the flow
field, and that tubes generally advance by processes that include flow inflation and tube coalescence. Flow inflation is
commonly followed by the formation of major, first-order ephemeral vents which, in turn, form an arterial tube network.
Tube coalescence occurs when lava breaks through the roof or wall of an older lava tube; this can result in the unexpected
appearance of vents several kilometers downstream. A close examination of underground features allowed us to distinguish
between ephemeral vent formation and tube coalescence, both of which are responsible for abrupt changes in level or flow
direction of lava within tubes on Etna. Ephemeral vent formation on the surface is frequently recorded underground by a
marked increase in size of the tube immediately upstream of these vents. When the lining of an inflated tube has collapsed,
‘a‘a clinker is commonly seen in the roof and walls of the tube, and this is used to infer that inflation has taken place in the
distal part of an ‘a‘a lava flow. Tube coalescence is recognised either from the compound shape of tube sections, or from
breached levees, lava falls, inclined grooves or other structures on the walls and roof. Our observations confirm the
importance of lava tubes in the evolution of extensive pahoehoe and ‘a‘a flow fields on Etna.

grant from the commission of the European Communities under the Fourth Framework Programme, Environment and Climate, Contract ENV4-CT97-0713.

Anonymous, 1669. An answer to some inquiries about the late
eruption of Mount Aetna on 1669. Communicated by some
inquisitive English merchants now residing in Sicily. Philos.
Trans. R. Soc. London 51, 1028–1034.
Atkinson, A., Atkinson, V., 1995. Undara Volcano and its lava
tubes. Vernon and Anne Atkinson, Brisbane, Queensland, p.
85.
Atkinson, A., Griffin, T.J., Stephenson, P.J., 1975. A major lava
tube system from Undara Volcano, North Queensland. Bull.
Volcanol. 39, 266–293.
Balsamo, A., Priolo, A., Priolo, G., Sanfilippo, G., Scammacca,
B., 1994. Grotte vulcaniche di Sicilia, notizie catastali: quarto
contributo da Si CT 76 a Si CT 100.. Boll. Accad. Gioenia
Sci. Nat. Catania 27, 173–212.
Bonforte, A., 1994. Evoluzione del campo lavico dell’eruzione
etnea 1991–93. Universita degli studi di Catania, unpublished
degree second thesis, 85 pp.
Brunelli, Scammacca, 1975. Grotte vulcaniche di Sicilia.
Calvari, S., Pinkerton, H., 1998. Formation of lava tubes and
extensive flow field during the 1991–93 eruption of Mount
Etna. J. Geophys. Res. 103, 27291–27302.
Calvari, S., Coltelli, M., Neri, M., Pompilio, M., Scribano, V.,
1994a. The 1991–93 Etna eruption: chronology and geological
observations. Acta Vulcanol. 4, 1–15.
Calvari, S., Groppelli, G., Pasquare´, G., 1994b. Preliminary geological
data on the south–western wall of the Valle del Bove,
Mt. Etna, Italy. Acta Vulcanol. 5, 15–30.
Cavallaro, F., Puglisi, G., Tranchina, A., 1985. Morfologia e
petrografia di colate con ‘lava tubes’ del basso versante sudorientale
dell’Etna. Boll. Accad. Gioenia Sci. Nat. Catania 18,
305–324.
Corsaro, R., Giudice, G., Puglisi, G., 1990. Il sistema 3 livelli-ktm:
studio comparato di una colata con gallerie di scorrimento
lavico. Atti del 18 Convegno Regionale di Speleologia della
Sicilia, Ragusa, 66–76.
Cucuzza Silvestri, S., 1977. Le grotte vulcaniche dell’Etna e il
loro studio. Atti del Seminario sulle Grotte Laviche, Catania,
215–229.
Cumin, G., 1954. L’eruzione laterale etnea del novembre 1950–
dicembre 1951. Bull. Volcanol. 15, 3–70.
Fanciulli, F., Licitra, G.M., Pandolfo, C., Puglisi, G., 1989.
Contributo alla conoscenza di alcune grotte vulcaniche in
territorio di Adrano. Centro Speleologico Etneo 1–11.
Frazzetta, G., Romano, R., 1984. The 1983 Etna eruption: event
chronology and morphological evolution of the lava flow.
Bull. Volcanol. 47, 1079–1096.
Giudice, G., Leotta, A., 1995. Le alchimie di un vulcano: la
Grotta Cutrona. Speleologia 33, 14–20.
Greeley, R., 1971. Observations of actively forming lava tubes
and associated structures, Hawaii. Modern Geol. 2, 207–223.
Greeley, R., 1987. The role of lava tubes in Hawaiian volcanoes.
U.S. Geol. Surv. Prof. Pap. 1350, 1589–1602.
Greeley, R., Hyde, A., 1972. Lava tubes in the Cava Basalt,
Mount St. Helens, Washington. Bull. Geol. Soc. Am. 83,
2397–2418.
Greeley, R., Fagents, S.A., Harris, R.S., Kadel, S.D., Williams,
D.A., Guest, J.E., 1998. Erosion by flowing lava: field evidence.
J. Geophys. Res. 103, 27325–27346.
Guest, J.E., Underwood, J.R., Greeley, R., 1980. Role of lava
tubes in flows from the Observatory Vent, 1971 Eruption on
Mount Etna. Geol. Mag. 117, 601–606.
Guest, J.E., Wood, C., Greeley, R., 1984. Lava tubes, terraces and
megatumuli on the 1614-24 pahoehoe lava flow field, Mount
Etna, Sicily. Bull. Volcanol. 47, 635–648.
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.
Hallworth, M.A., Huppert, H.E., Sparks, R.S.J., 1987. A laboratory
simulation of basaltic lava flows. Modern Geol. 11,
93–107.
Huppert, H.E., Sparks, R.S.J., 1985. Komatiites I: eruption and
flow. J. Petrol. 26, 694–725.
Huppert, H.E., Sparks, R.S.J., Turner, S.J., Arndt, N.T., 1984.
Emplacement and cooling of komatiite lavas. Nature 309,
19–22.
Jaggar, T.A., 1931. Lava stalactites, stalagmites, toes, and
‘squeeze-ups’. The Volcano Letter 345, 1–3.
Kauahikaua, J., Cashman, K.V., Mattox, T.N., Heliker, C., Hon,
K., Mangan, M., Thornber, C., 1998. Observations on basaltic
lava streams in tubes from Kilauea Volcano, Hawaii. J. Geophys.
Res. 103, 27303–27324.
Keszthelyi, L., 1995. A preliminary thermal budget for lava tubes
on the Earth and planets. J. Geophys. Res. 100, 20411–20420.
Keszthelyi, L.P., Pieri, D.C., 1993. Emplacement of the 75-kmlong
Carrizozo lava flow field, south–central New Mexico. J.
Volcanol. Geotherm. Res. 59, 59–75.
Kilburn, C., 1989. Surfaces of ‘a‘a flow-fields on Mount Etna,
Sicily: morphology, rheology, crystallization and scaling phe-
nomena. In: F.J. F.J.., Lava Flows and Domes. Springer-
Verlag, pp. 129–156.
Kilburn, C.R.J., Lopes, R.M.C., 1991. General patterns of flow
field growth: ‘a‘a and blocky lavas. J. Geophys. Res. 96,
19721–19732.
Leotta, A., 1994. Caratteristiche generali delle fratture eruttive
sull’Etna. Boll. Accad. Gioenia Sci. Nat. Catania 27, 153–160.
Lyell, C., 1858. On the structure of lavas which have consolidated
on steep slopes; with remarks on the mode of origin of Mount
Etna, and on the theory of ‘craters of elevation’. Philos. Trans.
R. Soc. London 148, 703–786.
Mattox, T.N., Heliker, C., Kauahikaua, J., Hon, K., 1993. Development
of the 1990 Kalapana flow field, Kilauea Volcano,
Hawaii. Bull. Volcanol. 55, 407–413.
Ollier, C.D., Brown, M.C., 1965. Lava caves of Victoria. Bull.
Volcanol. 28, 215–229.
Peterson, D.W., Swanson, D.A., 1974. Observed formation of lava
tubes. Studies in Speleology 2, 209–222.
Peterson, D.W., Holcomb, R.T., Tilling, R.I., Christiansen, R.L.,
1994. Development of lava tubes in the light of observations at
Mauna Ulu, Kilauea Volcano, Hawaii. Bull. Volcanol. 56,
343–360.
Pinkerton, H., Norton, G., 1995. Rheological properties of basaltic
lavas at sub-liquidus temperatures: laboratory and field measurements
on lavas from Mount Etna. J. Volcanol. Geotherm.
Res. 68, 307–323.
Pinkerton, H., Sparks, R.S.J., 1976. The 1975 subterminal lavas,
Mount Etna: a case history of the formation of a compound
lava field. J. Volcanol. Geotherm. Res. 1, 167–182.
Puglisi, G., 1981. La grotta ‘Micio Conti’. Studio genetico ed
evolutivo di una grotta di scorrimento lavico. Speleoetna-
Notiziario del Gruppo Grotte di Catania 3, 22–30.
Recupero, A., 1815. Storia naturale e generale dell’Etna. Catania,
pp. 85–97.
Romano, R., Sturiale, C., 1982. The historical eruptions of Mt.
Etna volcanological data.. Mem. Soc. Geol. Ital. 23, 75–97.
Romano, R., Amore, C., Atzori, P., Carter, S.R., Cristofolini, R.,
Di Geronimo, I., Di Grande, A., Duncan, A.M., Ferrara, V.,
Ghisetti, F., Guest, J.E., Hammill, M., Lentini, F., Lo Giudice,
E., Patane´, G., Pezzino, A., Puglisi, D., Rasa`, R., Schiliro`, F.,
Sturiale, C., Torre, G., Vezzani, L., 1979. Geological Map of
Mt. Etna. Progetto Finalizzato Geodinamica, C.N.R.-I.I.V.
Sparks, R.S.J., Pinkerton, H., 1978. Effect of degassing on rheology
of basaltic lava. Nature 276, 385–386.
Stephenson, P.J., 1996. Ridges and Depressions in the Undara
Lava Flow, North Queensland: Alternative Mechanisms for
their Formation. Chapman Conference on Long Lava Flows,
Townsville, Australia, 82–83.
Stevens, N.F., Murray, J.B., Wadge, G., 1997. The volume and
shape of the 1991–1993 lava flow field at Mount Etna, Sicily.
Bull. Volcanol. 59, in print.
Swanson, D.A., 1972. Magma supply rate at Kilauea Volcano,
1952–1971. Science 175, 169–170.
Tanguy, J.C., 1981. Les eruptions historiques de l’Etna: chronologie
et localisation. Bull. Volcanol. 44, 585–640.
Wadge, G., 1978. Effusion rate and the shape of ‘a‘a flow-fields
on Mount Etna. Geology 6, 503–506.
Wadge, G., 1981. The variation of magma discharge during
basaltic eruptions. J. Volcanol. Geotherm. Res. 11, 139–168.
Walker, G.P.L., 1971. Compound and simple lava flows and flood
basalts. Bull. Volcanol. 35, 579–590.
Walker, G.P.L., 1991. Structure, and origin by injection of lava
under surface crust of tumuli, ‘lava rises’, ‘lava-rise pits’, and
‘lava-inflation clefts’ in Hawaii. Bull. Volcanol. 53, 546–558.
Williams, D.A., Lesher, C.M., 1996. AnalyticalrNumerical Modeling
of Long Komatiite Flows. Chapman Conference on Long
Lava Flows, Townsville, Australia, 96–97.
Wood, C., 1971. The nature and origin of Raufarho´lshellir. Trans.
Cave Research Group of Great Britain 13, 245–256.
Wood, C., 1974. The genesis and classification of lava tube caves.
Trans. British Cave Research Assoc. 1, 15–28.
Wood, C., 1975. Factors contributing to the genesis of caves in
lava. Seminario sulle Grotte Laviche, Catania, 101–113.