Encyclopedia of Planetary Landforms
DOI 10.1007/978-1-4614-9213-9_62-1
# Springer Science+Business Media New York 2014
Composite Volcano
Dávid Karátson*
Department of Physical Geography, Eötvös Loránd University, Budapest, Hungary
Definition
“Relatively large, long-lived constructional volcanic edifice, comprising lava and volcaniclastic
products erupted from one or more vents. . .” (Davidson and de Silva 2000).
Note
The previous but still existent name “stratovolcano” implied alternating layers of lava and pyroclastic rocks. However, the more recent term “composite volcano” better describes the complex
architecture of this volcano type, superimposed occasionally by lava domes, dotted by scoria cones,
cut through by secondary vents, etc., giving a more complex structure relative to the textbook
“pancake” images.
Category
A type of ▶ volcano
Closely related to ▶ highland paterae
Synonyms
Composite cone; Stratovolcano
Description
In a mature stage, composite volcanoes are prominent features, larger than scoria cones, lava domes,
and other monogenetic volcanoes and steeper than shield volcanoes. Although they are all steep and
high landforms, they have different shapes including the regular, symmetrical “cones” (which are
not cones sensu stricto since bordered typically by a concave curve in profile view) to irregular,
multiple edifices often called “compound volcanoes.” On Earth, we have evidence that composite
volcanoes are built up by dominant lava effusion and, to a smaller extent, a wide range of explosive
eruptions. The size and frequency of explosivity may highly vary depending on tectonic setting,
lithology, and a number of other factors (e.g., magmatic or phreatomagmatic H2O). Remarkably,
although explosive events can be frequent at any composite volcano, the role of large explosions in
forming the volcano, especially those >VEI 3 [volcanic explosivity index], seems to be
*Email: dkarat@ludens.elte.hu
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Fig. 1 Volcán Parinacota in the Central Andes, Chile (Photo by D. Karátson)
insignificant, because in the latter case the resultant pyroclastic products are deposited distally
(several tens of kilometers far from center).
During their growth, composite volcanoes may be affected by various endo- and exogenic
processes that destroy the simple, regular, and initial shape. This general (although highly variable)
evolutionary scheme results in several subtypes with diverse morphometry.
Morphometry
Composite volcanoes reach absolute elevations 7,000 m in the Central Andes (i.e., Ojos del
Salado, world’s highest, 6,887 m; Sajama 6,542 m; Parinacota 6,348 m; ca. 50 volcanoes
>6,000 m a.s.l.) and 5,500 m from sea floor (e.g., Queen’s Mary Peak 2,062 m a.s.l). However,
in the Central Andes they emerge from the 4,000 m high Altiplano, whereas underwater buoyancy
contributes to the anomalous elevation. In fact, if their relative height is considered in the continents,
composite volcanoes do not exceed 2,500–3,000 m, their size being controlled by structural
conditions specific of Earth.
Morphometric studies on composite volcanoes have recently been improved benefitting from
digital elevation model (DEM) data, but the basic parameters were already documented by Wood
(1978). Among others, Wood found that basal cone width (Hco) ranges up to 22 km, crater width
(Wco) 700 m, and crater depth 450 m. Studying 26 most historically active cones in the
circumpacific region, he calculated a relationship Hco ¼ 0.122 Wco + 0.45. In another key paper,
Wadge (1982) calculated typically some tens to occasionally some hundreds of km3 volume of
composite volcanoes. These calculations were confirmed recently by DEM-based studies (Grosse
et al. 2009). An anomalous composite volcano, Mt. Etna, has a volume of 1,400 km3.
Many volcanoes tend to grow during evolution. If so, they may have a progressively smaller slope
on average: Wood (1978) calculated a decrease from 33 to 15 . This decrease can be attributed not
to the conical upper part, which keeps its slope, but to the progressively developing, enlarging lower
flanks and apron. As for the upper cone, Karátson et al. (2010) calculated a 28 average slope and
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Fig. 2 Circularity of selected stratovolcanoes on Earth (Karátson et al. 2010). Single cones may reach a circularity
>0.9, whereas more compound shapes are much less circular
34 maximum slope for the 19 most symmetric stratovolcanoes on Earth. These authors, examining
the circularity of these superb, symmetrical edifices, found that, whereas slight elongation or
irregularity of composite volcanoes results in a circularity 0.7–0.9, the circularity of the most
symmetrical ones may exceed 0.9 (Fig. 2).
Subtypes
Composite volcanoes may include the following shape variations. Note that there is no consensus on
classification (cf. Macdonald 1972; Davidson and de Silva 2000; Grosse et al. 2009):
(A) Concave, regular-shaped cone
(B) Irregular cone, which can be a simple or a compound (amalgamated or adjoined) volcanic
edifice, e.g., a twin volcano
(C) Truncated cone, either of the former two subtypes with summit caldera (circular, unbreached, or
open depression on top)
(D) Caldera volcano having a considerable (several km-large) depression that lowers the height of
the original cone (or cones) to an extent that the resultant landform may have even a negative
topography
These subtypes may represent occasionally an evolutionary trend, during which a simple landform evolves to a multiple cone then undergoes summit caldera formation. There is little evidence,
however, whether there occurs a real trend from simplicity to complexity. In fact, such a trend seems
to be opposed, for example, by a great number of extinct, tens of millions of year-old fossil
landforms with a simple cone remnant in the Central Andes (where low erosion has preserved the
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original geomorphic configuration: cf. Karátson et al. 2012). On the contrary, huge and long-lived
“caldera volcanoes” in Japan (Aso caldera), the USA (Valles caldera), etc., do exemplify complex
evolution of composite structures, many times nested depressions, in which single edifices are
unified time by time in huge calderas/tectonic depressions and then post-caldera volcanism creates
again intra- or extra-caldera single to multiple centers (cones, lava domes, etc.).
Detailed Description of Subtypes
Regular-Shaped Cones
Recent studies (Karátson et al. 2010) have shown that the simplest “textbook” profile of composite
volcanoes follows a logarithmic curve in the lower part, as has long been proposed (e.g., Milne
1878). This means that, certainly, these concave features are not “cones” sensu stricto (i.e., having a
linear profile). However, for a distinct population of the regular-shaped volcanoes, the profile indeed
becomes linear (straight) in the upper part (see “Formation”), having a “conical” topmost portion
(Fig. 1).
The regular-shaped composite volcano may retain its symmetrical cone shape for a long time. As
it was demonstrated (Karátson et al. 2010, 2012), there is a significant volumetric variation between
regular-shaped volcanoes, implying a proportional growth of the cone.
Irregular Cones
Regular symmetry becomes distorted when the volcano has a (much) longer lifetime or the eruptive
vent is multiplied or shifted (Davidson and de Silva 2000; Grosse et al. 2009). Irregular composite
volcanoes are grouped into “sub-cones” and “massifs” by Grosse et al. (2009, see “Formation”), but
there are a number of terms such as twin volcano, compound volcano, etc. Well-known twins in the
Central Andes include Atitlán–Tolimán, Fuego–Acatenango, and San Pedro–San Pablo. Adjoined
volcanic edifices can also be termed “clusters.” An important background factor of the more and
more complicated shape is certainly the tectonic effect, when faulting determines the growth
direction and growth pattern of the volcano.
Truncated Cones
At a certain point, the growing, expanding cone will be weakened and liable to collapse. This means
the detachment of a lateral portion of the upper cone transferring into in a debris avalanche (also see
“Formation”). Morphologically, the upper cone may be significantly lowered (e.g., from 2,950 to
2,550 m at Mt. St. Helens in 1980), and the resultant landform is a wide half-depression open toward
the direction of the collapse. (Notably, this asymmetric “half-caldera” is not a caldera sensu stricto,
i.e., not related to the circular collapse of the top connected to large-scale explosive eruptions at
many composite volcanoes.) The dimensions of a half caldera can be typically 2–3 km in diameter
and several hundred meters in depth (Siebert 1984). Such features have been widely recognized
subsequent to the famous 1980 eruption of Mt. St. Helens, and it turned out that the sector collapse is
a regular phenomenon occurring at composite volcanoes in various settings (e.g., Mt. Shasta, USA;
Popocatépetl, Mexico; Socompa, Parinacota, Chile; Dominika, Lesser Antilles; Roque Nublo, Gran
Canaria), that is, including “classical,” concave-shaped stratocones, compound volcanoes, and lava
dome groups both in subduction zones and hotspots. Theoretically, sector collapse may occur in
three ways: Bezymianny type, associated with explosion (commonly lateral blast); Bandai-san type,
associated by phreatic activity; and Unzen or Ontake type, accompanied by only tectonic
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Fig. 3 Out of the most regular-shaped composite volcanoes, conical (C-type) and parabolic (P-type) volcanoes can be
distinguished (Karátson et al. 2010). (a): C-type (conical) volcanoes have more constant and steep (30.3 on average)
upper slopes due mostly to ballistic ejecta deposited and stabilized by posteruptive slope processes at high repose angle.
(b) End of logarithmic profile at relatively steep slope angle. (c) P-type (parabolic) volcanoes have less steep (27.7 ) and
more curved slopes due to relatively larger quantity of short lava flows near the summit. (d) End of logarithmic profile at
moderate slope angles
phenomena (e.g., faulting or at most earthquakes). However, there might be mixed and transitional
origins (see “Formation”).
Caldera Volcanoes
Violent magmatic (e.g., subplinian, plinian) explosions cause a more significant and preferably
symmetric collapse of the whole upper part of a composite volcano. This process results in the
creation of a medium (6–8 km) or large (8–25 km) depression. In case of the former, the original
composite volcano may remain a positive although low landform, whereas in case of the latter, the
volcano as an edifice may disappear, and there remains only a “hole-in-the-ground” enormous
depression (e.g., Aso, Japan).
Formation
Composite volcanoes are common on Earth, but they are very rare in the Solar System. The reason of
the difference in planetary distribution lies, above all, in the presence or lack of active plate tectonics,
in particular, subduction, which is mostly responsible for explosivity, a key factor in forming
composite volcanoes. Nevertheless, hot spot volcanism without plate tectonics, widespread not
only on Earth but also in the evolution of Mars and Venus (and still existent on Io), can also produce
explosive eruptions, although under different physical conditions than on Earth. Therefore, although
rarely, composite volcanoes occur in extraterrestrial settings as well.
It is generally accepted that, on Earth, simple composite volcanoes develop from large, atypical
scoria cones issuing out abundant lava flows and exhibiting a range of eruptive styles. Well-known
examples of small, young composite volcanoes include Izalco, El Salvador (Carr and Pontier 1981),
and Cerro Negro, Nicaragua (McKnight and Williams 1997). A key point in the evolution is when
low-explosivity (i.e., scoria fall) eruptions change into more powerful ones, and at the same time
viscous lavas start to increase cone height. In fact, at several composite volcanoes, the uppermost
part is expanded by small-volume but stubby lava flows/domes (Davidson and de Silva 2000).
Extrusion of these lavas each time increases edifice height with a relatively small volume. Later on,
significant volumes can be added via accumulation on the lower flanks and the apron with no or
minor height increment.
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Fig. 4 Possible evolutionary paths of composite volcanoes (Grosse et al. 2009)
Karátson et al. (2010) studied the most regular-shaped stratovolcanoes of Earth (Fig. 2). Within
the highly symmetrical shapes, they distinguished those with a concave profile (P, parabolic type)
and those with a linear profile (C, conical type, i.e., having a real cone in the upper part: Fig. 3). They
proposed that, apart from occasional large explosive eruptions characterizing both subtypes without
shaping the upper cone, C-type volcanoes have higher SiO2 and/or higher H2O content, implying a
higher frequency of mildly explosive (e.g., strombolian) eruptions. These small-scale explosions, in
turn, may be responsible for forming the constant uppermost slopes resembling a scoria cone. By
contrast, P-type volcanoes have a higher incidence of effusive events and/or a lower incidence of
upper flank-forming (i.e., mild) explosive eruptions. Therefore, their concave upper flanks may be
shaped typically by lava flows.
As a composite volcano grows up in a relatively short time (see “Age”), Davidson and da Silva
(2000) suggested two factors that may decrease the eruption rate. First, the growing mass of the
volcano increases the lithostatic load which eventually overcomes the pressure of the magma
chamber. Second, in order to erupt, the magma needs to ascend progressively larger distances to
the surface. These factors result sooner or later in the opening of parasitic vents and the lateral
expansion of the volcano. According to Grosse et al. (2009), there might be a critical height range,
from where the volcano may follow a distinct evolutionary path and grows laterally. Such an
evolutionary trend is depicted in Fig. 4 distinguishing the abovementioned cones, sub-cones (i.e.,
elliptical cones), and massifs. Obviously, the lateral expansion of a volcano is also controlled by
tectonic faulting, determining how additional vents develop.
Another process contributing to volcano asymmetry is the partial failure of the growing volcano,
also called sector collapse. There are several known factors behind this process: volcano emplacement on a dipping surface, volcano spreading, instable upper part due to loose, fragmented material
and/or asymmetric growth, and hydrothermal alteration that weakens the edifice. Many times, a
number of these factors conspire to cause edifice failure.
Volcanic calderas, as mentioned above, form at composite volcanoes by concentric edifice
collapse as a result of large explosive eruptions. Magma supply, volatile concentration, and
changing dimensions of vent during the eruption control the style and fate of an explosive process,
that in turn may lead to more or less symmetric caldera collapse. Several types of calderas (e.g.,
funnel, downsag, piecemeal, trapdoor) have been distinguished (e.g., Lipman 1997). Tectonic
control (e.g., at Lake Toba) may also contribute to the creation of enormous negative landforms.
Notably, the largest caldera volcanoes may be created via the collapse of a cluster of pre-caldera
edifices, and vice versa they may host several post-caldera centers subsequently (e.g., Aso caldera,
Japan, Valles caldera, USA).
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Fig. 5 Degradation of a volcanic cone under “average” climate (After Cotton 1952 and several authors): (1) original
cone, (2) planèze stage, (3) residual stage, (4) skeleton stage
Age (on Earth)
In contrast to monogenetic scoria cones, composite volcanoes may be active for a long time.
However, surprisingly short time is required to construct a single composite volcano
1,500–2,000 m high. For example, the grow-up of Mt. St. Helens (Washington, USA) lasted for
<40–50 ka, Sakurajima (Japan) <13 ka, Fuji young (present) cone (Japan) <11 ka, Parinacota
young cone (Chile) <10(20) ka, Kliuchevskoi, Kamchatka (Russia) <7 ka, and Cotopaxi (Ecuador)
<5 ka, whereas Vesuvius central cone has only built up since the Pompeii eruption in AD 79 (for
more details on volcanoes’ eruptive activities, see Global Volcanism Program (www.volcano.si.
edu).
On the other hand, composite volcanoes can be long-living features. Not to speak about complex,
large caldera volcanoes, individual volcanic edifices – progressively becoming compound
features – may also be active on a million-year scale. For example, Mt. Adams, Oregon, USA,
began to form 940 ka ago (Hildreth and Lanphere 1994). Since that time, the intensity of eruptions
has been highly variable: major cone building stages occurred between 520–490, 460–425, and
40–10 ka ago. During these stages, the eruption flux (so-called peak rate) ranged between 1.6 and
5 km3/ka (very high values in a worldwide context), whereas during less intense periods, the
so-called background rate was 0.05 to 1 km3/ka. At Parinacota, Chile, Hora et al. (2007) calculated
0.75–1.0 1 km3/ka peak rates for the new cone building stage (10 or 20 ka to present).
Degradation
Composite cones follow an erosional pathway recognized by several authors (cf. Cotton 1952;
MacDonald 1972; Ollier 1988; Francis 1993; Karátson et al. 1999). Rules of this process are
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Fig. 6 Circularity of an undissected and dissected cone can be equally high (Karátson et al. 2010)
governed by the role and proportion of erosional processes (e.g., linear erosion of commonly
running water as opposed by areal degradation by, e.g., glacial erosion), the erosional resistance
of segments or layers within the volcano, and the shape of the volcano. In the simplest case, under
typical, “average” climates (i.e., with more or less rainfall and without intense glacial erosion that
rapidly decapitates the upper cone), the volcano is commonly degraded in four steps (Fig. 5). First,
during the original cone stage, the outer flanks are dissected by a radial drainage. Notably, despite
intense dissection (Fig. 6), the original circular symmetry can be maintained for a long time. The
radial drainage soon turns into a dendritic one. During this process, the hydrographically strongest
water course drains the central crater or caldera which becomes open and elongated to one preferred
direction (of the main outlet valley, e.g., Mt. Taylor, New Mexico, USA). Second, as dendritic
drainage results in some major sub-catchment areas on the flanks, some portions in between these
catchments and having less developed drainage pattern erode to a smaller extent and will remain as
remnant surfaces for a long time (planèze stage). Third, all remnant surfaces are degraded, and the
cone shape is recognizable only by the radial drainage pattern (residual stage). The central depression may disappear or survive as a large catchment area with own drainage inherited from the
original crater or caldera. The fourth stage, called skeleton, unravels the core of the volcano, that is,
the more resistant internal structure (central subvolcanic body, feeding vents, dykes, occasional
resistant peripheral parts of the edifice). On Earth, such a stage can be traced back to the Oligocene
age under arid climates (e.g., Summer Coon, Nevada, USA).
Peculiar residual-stage composite volcanoes can be recognized in the Central Andes. There,
glacial erosion in the Pleistocene enhanced the radial outlet valley pattern, resembling an “edelweiss” in plan view (Fig. 7; Karátson et al. 2012). Under the prevailing semiarid to arid climates,
however, a great part of the original volcanoes even with an age of 15 Ma has been preserved.
The erosional process summarized above is certainly more complicated if a less symmetrical or
twin, compound edifice is subjected to external forces. Erosion of a symmetrical cone can also be
more diverse in case of rainfall asymmetry, non-horizontal emplacement of volcano, significant
resistance differences in inner structure, etc.
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Fig. 7 Radial valleys (with a peculiar “edelweiss pattern”) of residual-stage composite volcanoes in the Central Andes
(Karátson et al. 2012). Image is a SRTM DEM-based slope map with ridge enhancement
Fig. 8 Structure of a composite volcano: (b) bedrock; (baf ) block-and-ash flow, other pyroclastic flow, surge, and
pyroclastic fall deposits, debris-avalanche deposits; (cd) cryptodome; (d) dyke; (dd) debris-avalanche deposit; (ld) lahar
and fluvial deposits; (lf ) lava flow; (lp) lava plug; (m) magma chamber; (pc) buried parasitic crater; (pd) pyroclastic
deposits, mainly fall; (pdf ) pyroclastic flow deposit; (pv) parasitic vent; (sc) summit crater(s); (sd) summit lava dome; (v)
vent; and (va) volcaniclastic apron
Surface/Structural Units
The structure of composite volcanoes is depicted in Fig. 8. Their primary conical shape may be
complicated by a number of summit craters and lava domes, superimposed (i.e., parasitic) centers, or
summit calderas (see earlier). Basically, such a volcano has either a very simple, regular structure
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that can be called “ideal stratovolcano” or a more diverse structure called “lava dome group”
(Lockwood and Hazlett 2010). Although the former somewhat resembles the ideal “pancake”
structure, that is, interbedded lava flow and pyroclastic layers, in reality this subtype may also
show asymmetries, whereas the lava dome group is obviously asymmetrical (at least in the upper
cone). During composite cone evolution, typically a mixture or amalgamation of the two structures
develops.
Composition (on Earth)
In addition to explosivity, another – but interrelated – factor determining the construction of
composite volcanoes is magma composition. On Earth, the composition of the magma is largely
the result of differentiation and volatile concentration (Davidson and de Silva 2000). To build up a
composite volcano, relatively frequent eruptions from differentiated magma are required. Differentiation results in an increasing SiO2 content and increasing viscosity of magma, constructing upward
growing cones. By contrast, at shield volcanoes, low-viscosity and less silicic basalts can flow large
distances from the vent building up more gentle slopes and larger edifice (Davidson and de Silva
2000).
The typical composition of stratovolcanoes ranges commonly between 50–75 % SiO2, 1–6 K2O,
and 30–70 molar MgO/(MgO + FeOtot); see selected studies of Davidson and de Silva (2000),
Bindeman et al. (2004), Garrison et al. (2006), Figueroa et al. (2009), Karátson et al. (2010), and
Mamani et al. (2010) and the GEOROC database (Geochemistry of Rocks of the Oceans
and Continents, Max-Planck-Institut f€
ur Chemie in Mainz, Germany, http://georoc.mpch-mainz.
gwdg.de). Noteworthy, not only volcano populations in a regional setting but also individual
volcanoes and even their single eruptive phases may also show a large scatter of chemical
composition, reflecting magma evolution.
Prominent Examples (on Earth)
Regular-Shaped Cones
Mayon, Philippines; Kliuchevskoi and Kronotsky, Kamchatka, Russia; Cotopaxi, Ecuador;
Parinacota and Licancabur, Chile; Pavlof, Alaska, USA; Taranaki (Mt. Egmont), New Zealand;
and Fuji, Japan.
Irregular Cones
San Pedro–San Pablo, Chile; Tongariro, New Zealand; Pacaya, Guatemala; and Mt. Rainier,
Washington, USA.
Truncated Cones
Mt. St. Helens, Washington, USA; Socompa, Chile-Argentina; and Bezymianny, Kamchatka,
Russia.
Caldera Volcanoes
Crater Lake, Oregon, USA; Pinatubo, Philippines; Somma, Italy; Aniakchak, Alaska, USA; and
Tejeda, Tenerife, Spain.
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Fig. 9 Proposed composite volcano on Mars: Apollinaris Mons. THEMIS day IR mosaic. (Oc) outer caldera; (Ic) inner
caldera; (Pd) possible pyroclastic deposits; (Fs) flank slumps; (Bs) basal scarp; (CT) chaotic terrain; and (F) fan materials
(Lang 2009). (NASA/JPL-Caltech/Arizona State University)
Distribution
Composite volcanoes are one of the most characteristic landforms on Earth but are very rare on other
Solar System bodies.
Composite volcanoes can occur in almost all tectonic settings. Actually, the only factor is the
presence of enough volatiles, differentiated magma, and considerable magma supply. These criteria
are matched first of all at subduction zones; hence the circumpacific “Ring of Fire” is the primary
location of composite volcanoes, including various island arcs (e.g., Aleutian, Kuril, and Japan
islands, The Philippines, Indonesia, New Zealand) and continental margins (e.g., Cascades, Andes).
However, hot spots, rift zones, and other less-defined settings within lithospheric plates may also
host composite volcanoes (e.g., Canarian Islands, Iceland, Sicily, East Africa, Antarctica, Iran).
Significance
Composite volcanoes, as discussed above, are created under specific conditions that are only
available almost exclusively on Earth. Studying and defining these conditions may cast light on
the early evolution of our planet and the divergent history relative from Mars and Venus and may
decipher the specific role of volcanic activity in Earth’s life. Moreover, since several of the great
eruptions have been related to composite volcanoes, resulting in significant effects on large regions
including ecology and even society, by even causing climate changes, the study of composite
volcanoes can contribute to our knowledge on the history of mankind as well.
Planetary Analogs
On Mars, explosive eruptions have been proposed to occur more frequently than previously thought
(Stewart and Head 2001). In Aeolis quadrangle, Apollinaris Mons (formerly Apollinaris Patera,
Fig. 9) and associated volcanic constructs (e.g., Zephyria Tholus) (Werner 2009) are candidates of
being composite structures resulting from both effusive and explosive activity. Apollinaris Mons is
not a ▶ highland patera (it is located along the northern lowland-southern highland transition),
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although it contains many geomorphic similarities, including a large central caldera and extensively
channeled and dissected flanks (Lang 2009). Notably, Martian composite volcanoes are characterized by different explosive processes and more gentle slopes which may be a result of lower gravity
(see e.g., Osinski et al. 2011; Kleinhans et al. 2011). Zephyria Tholus is an “unusually symmetrical
cone” 30 km wide and 2–2.5 km high with a summit caldera (Stewart and Head 2001). Head and
Wilson (1998) proposed that Tharsis volcanoes may have had a significant component of explosive
volcanism and by definition they should be classified as composite, and not shield volcanoes, even if
they display abundant lava flows.
Although very large, flat-topped Martian constructs resemble mafic ▶ tuyas emplaced under thick
(<2 km) temperate ice, it is suggested that they may be polygenetic stratovolcanoes, formed
subglacially either within very thick ice or as multiple superimposed lava-fed deltas emplaced in
thinner ice that formed after eruptions (Smellie 2009). Classical tuyas differ from composite
volcanoes with their flat top and absence of crater (on Earth e.g., in Iceland, Kamchatka).
Other planets do not show features that may be classified as composite volcanoes. However, on
Jupiter’s moon Io, there is abundant evidence of explosive eruptions, which imply the possibility of
the formation of composite structures (i.e., of lava and pyroclastic rocks). In fact, the Voyager and
Galileo flybys photographed some conical volcanoes in addition to the common shields and paterae
(Williams et al. 2011), and, exceptionally, Tohil Mons has been proposed as a silicic volcano
composed of dense, viscous lava flows and controlled by strong tectonics (Hargitai and Karátson
2003) or, alternatively, as a tectonically disrupted, ridged-and-grooved crustal block (Williams
et al. 2004).
Terrestrial Analog of Proposed Martian Examples
For sub-ice composite volcanoes: James Ross Island stratovolcano in Antarctica (Smellie 2009).
History of Investigation
Being the most dangerous and prominent kind of volcanoes in the continents, stratovolcanoes have
long been recognized as a fundamental edifice type. William Hamilton drew sketches on the
changing shape of Vesuvius in 1767. However, the first thorough study has been published by
Milne in only 1878, focusing on the regular stratovolcano shape. Cotton (1944, 1952) gave a
discussion on origin and construction, whereas MacDonald (1972) and Pike and Clow (1981) on
classification.
Systematic morphometric studies of composite volcanoes in relation to theoretical questions
began in the 1970s (e.g., Wood 1978; Lacey et al. 1981) and have been scarce since then. Francis
(1993), giving a modern overview in a volcanological context, reviewed the geometry of stratovolcano shape; Thouret (1999) published a bibliographic overview; and Davidson and da Silva (2000)
made a comprehensive study on composite cone evolution.
As discussed above, recently Grosse et al. (2009) proposed a classification and evolutionary
scheme for arc-related composite volcanoes, whereas Karátson et al. (2010) studied the regular
stratovolcano shape using an advanced digital elevation model analysis.
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Database
Volcanoes of the World series (3rd edition in 2010, edited by Siebert, L., Simkin, T., and
Kimberly, P.); Global Volcanism Program (www.volcano.si.edu); Volcano Live (www.
volcanolive.com); Cascades Volcano Observatory (http://vulcan.wr.usgs.gov); and Observatory of
Etna (www.ct.ingv.it/en).
Origin of Term
“Stratovolcano” is the classic term for composite volcanoes. Strato (from the Latin “stratum”)
implied a pancake structure of lava and pyroclastic rocks. Since such a concept does not match
the reality, a more flexible term “composite” volcano has come into practice since the 1980s. As
discussed above, Davidson and da Silva (2000) confirmed this terminology shift, giving priority to
“composite volcano.”
IAU Descriptor Term
▶ Patera, ▶ Mons, ▶ Tholus
See Also
▶ Highland Patera
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