Morphological complexities and hazards during the emplacement of channel-fed `a`a lava flow fields: A study of the 2001 lower flow field on Etna

Long-lived basaltic eruptions often produce
structurally complex, compound `a`a flow fields. Here we
reconstruct the development of a compound flow field
emplaced during the 2001 eruption of Mt. Etna (Italy).
Following an initial phase of cooling-limited advance, the
reactivation of stationary flows by superposition of new
units caused significant channel drainage. Later, blockages
in the channel and effusion rate variations resulted in
breaching events that produced two new major flow
branches. We also examined small-scale, late-stage
‘squeeze-up’ extrusions that were widespread in the flow
field. We classified these as ‘flows’, ‘tumuli’ or ‘spines’ on
the basis of their morphology, which depended on the
rheology, extrusion rate and cooling history of the lava.
Squeeze-up flows were produced when the lava was fluid
enough to drain away from the source bocca, but
fragmented to produce blade-like features that differed
markedly from `a`a clinker. As activity waned, increased
cooling and degassing led to lava arriving at boccas with a
higher yield strength. In many cases this was unable to flow
after extrusion, and laterally extensive, near-vertical sheets of
lava developed. These are considered to be exogenous forms
of tumuli. In the highest yield strength cases, near-solid lava
was extruded from the flow core as a result of ramping,
forming spines. The morphology and location of the
squeeze-ups provides insight into the flow rheology at the
time of their formation. Because they represent the final
stages of activity of the flow, they may also help to refine
estimates of the most advanced rheological states in which
lava can be considered to flow. Our observations suggest that
real-time monitoring of compound flow field evolution may
allow complex processes such as channel breaching and
bocca formation to be forecast. In addition, documenting the
occurrence and morphology of squeeze-ups may allow us to
determine whether there is any risk of a stalled flow front
being reactivated. This will therefore enhance our ability to
track and assess hazard posed by lava flow emplacement.

We thank INGV Catania for providing the images
used in our study. The work was funded by
Natural Environment Research Council studentship NER/S/A2005/
13681 and grant NE/F018010/1. MRJ was funded by the Royal Society.

Anderson SW, Fink JH (1990) The development and distribution of
surface textures at the Mount St-Helens dome. In: Fink JH (ed)
Lava flows and domes. Springer, Berlin, pp 25–46
Anderson SW, Fink JH (1992) Crease structures—indicators of
emplacement rates and surface stress regimes of lava flows. Geol
Soc Am Bull 104:615–625
Applegarth LJ (2008) Complexity in lava flows: surface features and
structural morphology, PhD thesis, Lancaster University
Bailey JE, Harris AJL, Dehn J, Calvari S, Rowland S (2006) The
changing morphology of an open lava channel on Mt. Etna. Bull
Volcanol 68:497–515
Behncke B, Neri M (2003) The July-August 2001 eruption of Mt.
Etna (Sicily). Bull Volcanol 65:461–476
Blake S (1990) Viscoplastic models of lava domes. In: Fink JH (ed)
Lava flows and domes. Springer, Berlin, pp 88–126
Borgia A, Linneman S, Spencer D, Morales LD, Andre JB (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
(52):653–656
Calvari S, Pinkerton H (2004) Birth, growth and morphologic
evolution of the “Laghetto” cinder cone during the 2001 Etna
eruption. J Volcanol Geotherm Res 132:225–239. doi:10.1016/
S0377-0273(03)00347-0
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. doi:10.1016/S0377-0273(02)00308-6
Cashman KV, Blundy J (2000) Degassing and crystallisation of
ascending andesite and dacite. Phil Trans Roy Soc London
358:1487–1513
Chester DK, Duncan AM, Guest JE, Kilburn CRJ (1985) Mount Etna:
the anatomy of a volcano. Chapman and Hall, London
Christiansen R, Lipman PW (1966) Emplacement and thermal history
of a rhyolite lava flow near Fortymile Canyon, southern Nevada.
Geol Soc Am Bull 77:671–684
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.
doi:10.1029/2006JF000598
Crisci G, Rongo R, Gregorio S, Spataro W (2004) The simulation
model SCIARA: the 1991 and 2001 lava flows at Mount Etna. J
Volcanol Geotherm Res 132:253–267
Crisp J, Baloga S (1994) Influence of crystallisation and entrainment
of cooler material on the emplacement of basaltic aa lava flows. J
Geophys Res 99:11819–11831
Dragoni M, Tallarico A (1996) A model for the opening of ephemeral
vents in a stationary lava flow. J Volcanol Geotherm Res 74:39–
47
Duncan AM, Guest JE, Stofan ER, Anderson SW, Pinkerton H,
Calvari S (2004) Development of tumuli in the medial portion of
the 1983 `a`a flow-field, Mount Etna, Sicily. J Volcanol Geotherm
Res 132:173–187
Favalli M, Pareschi M, Neri A, Isola I (2005) Forecasting lava flow
paths by a stochastic approach. Geophys Res Lett 32:L03305.
doi:10.1029/2004GL021718
Favalli M, Harris AJL, Fornaciai A, Pareschi MT, 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
Frazzetta G, Romano R (1984) The 1983 Etna eruption: event
chronology and morphological evolution of the lava flow. Bull
Volcanol 47:1079–1096
Guest JE, Stofan ER (2005) The significance of slab-crusted lava
flows for understanding controls on flow emplacement at Mount
Etna, Sicily. J Volcanol Geotherm Res 142:193–205
Guest JE, Underwood JR, Greeley R (1980) Role of lava tubes in
flows from the observatory-vent, 1971 eruption on Mount Etna.
Geol Mag 117:601–606
Guest JE, Kilburn CRJ, Pinkerton H, Duncan AM (1987) The
evolution of lava flow-fields: observations of the 1981 and
1983 eruptions of Mount Etna, Sicily. Bull Volcanol 49:527–
540
Harris AJL, Rowland SK (2001) FLOWGO: a kinematic thermorheological
model for lava flowing in a channel. Bull Volcanol
63:20–44
Harris AJL, Dehn J, Calvari S (2007) Lava effusion rate definition and
measurement: a review. Bull Volcanol 70:1–22
Bull Volcanol
Harris AJL, Favalli M, Mazzarini F, Hamilton CW (2009) Construction
dynamics of a lava channel. Bull Volcanol 71:459–474.
doi:10.1007/s00445-008-0238-6
Hidaka M, Goto A, Umino S, Fujita E (2005) VTFS project:
Development of the lava flow simulation code LavaSIM with a
model for three-dimensional convection, spreading, and solidification.
Geochem Geophys Geosys 6:Q07008. doi:10.1029/
2004GC000869
Hon K, Kauahikaua J, Denlinger R, Mackay K (1994) Emplacement
and inflation of pahoehoe sheet flows- observations and measurements
of active lava flows on Kilauea Volcano, Hawai’i. Geol
Soc Am Bull 106:351–370
Istituto Nazionale di Geofisica e Vulcanologia (Catania) syn-eruption
reports: http://www.ct.ingv.it/Etna2001/Main.htm
James MR, Pinkerton H, Robson S (2007) Image-based measurement
of flux variation in distal regions of active lava flows. Geochem
Geophys Geosys 8:Q03006. doi:10.1029/2006GC001448
James MR, Pinkerton H, Applegarth LJ (2009) Detecting the
development of active lava flow fields with a very-long-range
terrestrial laser scanner and thermal imagery. Geophys Res Lett
36:L22305. doi:10.1029/2009GL040701
Jurado-Chichay Z, Rowland SK (1995) Channel overflows of the
pohue bay flow, Mauna-Loa, Hawai’i- examples of the contrast
between surface and interior lava. Bull Volcanol 57:117–126
Kauahikaua J, Sherrod DR, Cashman KV, Heliker CC, Hon K, Mattox
TN, Johnson JA (2003) Hawai’ian lava-flow dynamics during the
Pu`u-`O`o-Kupaianaha eruption: a tale of two decades. US Geol
Surv 1676:63–87
Keszthelyi L (1995) A preliminary thermal budget for lava tubes on
the Earth and planets. J Geophys Res 100:20411–20420
Keszthelyi L, Self S (1998) Some physical requirements for the
emplacement of long basaltic lava flows. J Geophys Res
103:27447–27464
Kilburn CRJ (1981) Pahoehoe and `a`a-lavas- a discussion and
continuation of the model of Peterson and Tilling. J Volcanol
Geotherm Res 11:373–382
Kilburn C (1990) Surfaces of `a`a flow-fields on Mount Etna, Sicilymorphology,
rheology, crystallisation and scaling phenomena. In:
Fink JH (ed) Lava flows and domes. Springer, Berlin, pp 129–156
Kilburn CRJ, Lopes RMC (1988) The growth of `a`a lava flow-fields
on Mount Etna, Sicily. J Geophys Res 93:14759–14772
Kilburn CRJ, Lopes RMC (1991) General patterns of flow field
growth- `a`a and blocky lavas. J Geophys Res 96:19721–19732
Krauskopf KB (1948) Lava movement at Parícutin volcano, Mexico.
Geol Soc Am Bull 59:1267–1283
Lejeune AM, Richet P (1995) Rheology of crystal-bearing silicate
melts- an experimental-study at high viscosities. J Geophys Res
100:4215–4229
Lipman PW, Banks NG (1987) `A`a flow dynamics, Mauna Loa 1984.
US Geol Surv 1350:1527–1568
Luhr JF, Simkin T (1993) Parícutin, the volcano born in a Mexican
cornfield. Geoscience, Arizona
Macdonald GA (1972) Volcanoes. Prentice-Hall, New Jersey
Marsh BD (1981) On the crystallinity, probability of occurrence, and
rheology of lava and magma. Contrib Mineral Petrol 78:85–98
Mattox TN, Heliker C, Kauahikaua J, Hon K (1993) Development of
the 1990 Kalapana flow-field, Kilauea Volcano, Haiwai’i. Bull
Volcanol 55:407–413
Mattsson HB, Vuorinen J (2008) Emplacement and inflation of
natrocarbonatitic lava flows during the March–April 2006
eruption of Oldinyo Lengai, Tanzania. Bull Volcanol 71:301–
311. doi:10.1007/s00445-008-0224-z
Mazzarini F, Pareschi MT, Favalli M, Isola I, Tarquini S, Boschi E
(2005) Morphology of basaltic lava channels during the Mt. Etna
September 2004 eruption from airborne laser altimeter data.
Geophys Res Lett 32:L04305. doi:10.1029/2004GL021815
Nichols RN (1939) Squeeze-ups. J Geol 47:421–425
Peterson DW, Tilling RI (1980) Transition of basaltic lava from
pahoehoe to `a`a, Kilauea volcano, Hawai’i- field observations
and key factors. J Volcanol Geotherm Res 7:271–293
Pinkerton H, Sparks RSJ (1976) 1975 sub-terminal lavas, Mount Etnacase
history of formation of a compound lava field. J Volcanol
Geotherm Res 1:167–182
Pinkerton H, Stevenson RJ (1992) Methods of determining the
rheological properties of magmas at sub-liquidus temperatures.
J Volcanol Geotherm Res 53:47–66
Pinkerton H, Wilson L (1994) Factors controlling the lengths of
channel-fed lava flows. Bull Volcanol 56:108–120
Polacci M, Papale P (1997) The evolution of lava flows from
ephemeral vents at Mount Etna: insights from vesicle distribution
and morphological studies. J Volcanol Geotherm Res 76:1–
17
Polacci M, Papale P (1999) The development of compound lava fields
at Mount Etna. Phys Chem Earth A—Solid Earth and Geodesy
24:949–952
Rossi MJ, Gudmundsson A (1996) The morphology and formation of
flow-lobe tumuli on Icelandic shield volcanoes. J Volcanol
Geotherm Res 72:291–308
Rowland SK, Walker GPL (1987) Toothpaste lava: characteristics and
origin of a lava structural type transitional between pahoehoe and
`a`a. Bull Volcanol 49:631–641
Rowland SK, Walker GPL (1990) Pahoehoe and `a`a in Hawai’i:
volumetric flow rate controls the lava structure. Bull Volcanol
52:615–628. doi:10.1007/BF00301212
Sheth HC, Ray JS, Bhutani R, Kumar A, Smitha RS (2009)
Volcanology and eruptive styles of Barren Island: an active
mafic stratovolcano in the Andaman Sea, NE Indian Ocean. Bull
Volcanol 71:1021–1039. doi:10.1007/s00445-009-0280-z
Sparks RSJ, Pinkerton H (1978) Effect of degassing on rheology of
basaltic lava. Nature 276:385–386
Thordarson T, Self S (1998) The Roza Member, Columbia River
Basalt Group: A gigantic pahoehoe lava flow field formed by
endogenous processes? J Geophys Res 103:27411–27445
Vicari A, Herault A, Del Negro C, Coltelli M, Marsella M, Proietti C
(2007) Modelling of the 2001 lava flow at Etna volcano by a
Cellular Automata approach. Environ Model Softw 22:1465–
1471
Walker GPL (1973) Lengths of lava flows. Phil Trans Roy Soc
London A—Math Phys and Eng Sci 274:107–118
Walker GPL (1991) Structure, and origin by injection of lava under
surface crust, of tumuli, lava rises, lava-rise pits, and lavainflation
clefts in Hawai’i. Bull Volcanol 53:546–558
Wright R, Garbeil H, Harris AJL (2008) Using infrared satellite data
to drive a thermo-rheological/stochastic lava flow emplacement
model: a method for near-real-time volcanic hazard assessment.
Geophys Res Lett 35:L19307. doi:10.1029/2008GL035228