Springer Nature is making Coronavirus research free. View research | View latest news | Sign up for updates

Like a cannonball: origin of dense spherical basaltic ejecta


Cannonballs are rare spherical to sub-spherical eruptive products associated with basaltic explosive activity. The origin of cannonballs is still debated and subjected to a wide spectrum of different interpretations. In order to better understand the physicochemical mechanisms controlling the formation of these explosive products, we investigated the textural and chemical features of cannonballs from the Cerro Chopo monogenetic volcano (Costa Rica). These explosive products ubiquitously show a core domain with coalesced bubbles (30–36% porosity) wrapped in a dense rim domain with small, isolated bubbles (20–27% porosity). Both domains are identical in terms of bulk rock composition and mineral chemistry and are portions of the same magma batch. Results from combined petrological and thermodynamic modeling indicate that a low-viscosity (~20 Pa s) melt containing early-formed olivine phenocrysts (~9 vol.%) ascended from storage at a decompression rate of 0.5 MPa s−1 until it reached a depth of 4.5 km (equivalent to a pressure of ~150 MPa). While rising from depth to 4.5 km, the melt underwent rapid decompression (0.5–2.6 MPa s−1) and H2O exsolution, driving late-stage crystallization of the groundmass. The fast ascent velocity (21–110 m s−1) while rising between 4.5 km and the surface induced turbulent (Re >103), annular flow development in the uppermost region of the conduit. We propose that cannonballs represent blebs of fluid magmas that underwent shear-driven detachment from the annulus of magma lining the conduit walls at depths lower than 4.5 km. The formation of such cannonballs is dictated by magma transport dynamics of low-viscosity, phenocryst-poor, and volatile-rich melts that rapidly accelerate within the shallow conduit.

This is a preview of subscription content, log in to check access.

Fig. 1
Fig. 2
Fig. 3


  1. Alvarado GE, Pérez W, Vogel TA, Gröger H, Patiño L (2011) The Cerro Chopo basaltic cone (Costa Rica): an unusual completely reversed graded pyroclastic cone with abundant low vesiculated cannonball juvenile fragments. J Volcanol Geotherm Res 201(1):163–177. doi:10.1016/j.jvolgeores.2010.11.010

  2. Araña V, López J (1974) Volcanismo. Dinámica y Petrologı́a de sus Productos. ed. Itsmo, Madrid

  3. Ariskin AA, Nikolaev GS (1996) An empirical model for the calculation of spinel-melt equilibria in mafic igneous systems at atmospheric pressure: 1. Chromian spinels. Contrib Mineral Petrol 123(3):282–292. doi:10.1007/s004100050156

  4. Bacon CR (1990) Calc-alkaline, shoshonitic, and primitive tholeiitic lavas from monogenetic volcanoes near Crater Lake, Oregon. J Petrol 31(1):135–166. doi:10.1093/petrology/31.1.135

  5. Bednarz U, Schmincke HU (1990) Evolution of the Quaternary melitite-nephelinite Herchenberg volcano (East Eifel). Bull Volcanol 52(6):426–444. doi:10.1007/BF00268924

  6. Brown RJ, Valentine GA (2013) Physical characteristics of kimberlite and basaltic intraplate volcanism and implications of a biased kimberlite record. Geol Soc Am Bull 125(7–8):1224–1238. doi:10.1130/B30749.1

  7. Cristini V, Renardy Y (2006) Scalings for droplet sizes in shear-driven breakup: non-microfluidic ways to monodisperse emulsions. Fluid Dynamics and Material Processing 2(2):77–94

  8. Del Bello E, Llewellin EW, Taddeucci J, Scarlato P, Lane SJ (2012) An analytical model for gas overpressure in slug-driven explosions: insights into Strombolian volcanic eruptions. Journal of Geophysical Research, Solid Earth 117. doi:10.1029/2011JB008747

  9. Del Bello E, Lane SJ, James MR, Llewellin EW, Taddeucci J, Scarlato P, Capponi A (2015) Viscous plugging can enhance and modulate explosivity of strombolian eruptions. Earth Planet Sci Lett 423:210–218. doi:10.1016/j.epsl.2015.04.034

  10. Delpit S, Ross PS, Hearn BC (2014) Deep-bedded ultramafic diatremes in the Missouri River breaks volcanic field, Montana, USA: 1 km of syn-eruptive subsidence. Bull Volcanol 76(7):832. doi:10.1007/s00445-014-0832-8

  11. Dou HS, Khoo BC, Tsai HM (2010) Determining the critical condition for turbulent transition in a full-developed annulus flow. J Pet Sci Eng 73(1):41–47. doi:10.1016/j.petrol.2010.05.003

  12. Duan X (2014) A general model for predicting the solubility behavior of H2O–CO2 fluids in silicate melts over a wide range of pressure, temperature and compositions. Geochim Cosmochim Acta 125:582–609. doi:10.1016/j.gca.2013.10.018

  13. Francis PW (1973) Cannonball bombs, a new kind of volcanic bomb from the Pacaya volcano, Guatemala. Geol Soc Am Bull 84(8):2791–2794

  14. Giordano D, Russell JK, Dingwell DB (2008) Viscosity of magmatic liquids: a model. Earth Planet Sci Lett 271(1):123–134. doi:10.1016/j.epsl.2008.03.038

  15. Gonnermann HM, Manga M (2013) Chapter 4 – dynamic of magma ascent in the volcanic conduit. In: Fagents SA, Gregg TKP, Lopes RMC (eds) Modeling volcanic processes: the physics and mathematics of volcanism. Cambridge University Press, Cambridge, p 447

  16. Guilbaud MN, Siebe C, Agustín-Flores J (2009) Eruptive style of the young high-Mg basaltic-andesite Pelagatos scoria cone, southeast of México City. Bull Volcanol 71(8):859–880. doi:10.1007/s00445-009-0271-0

  17. Heiken G (1978) Characteristics of tephra from cinder cone, Lassen volcanic national park, California. Bull Volcanol 41(2):119–130. doi:10.1007/BF02597025

  18. Herd RA, Pinkerton H (1997) Bubble coalescence in basaltic lava: its impact on the evolution of bubble populations. J Volcanol Geotherm Res 75(1):137–157

  19. Houghton BF, Schmincke HU (1989) Rothenberg scoria cone, East Eifel: a complex Strombolian and phreatomagmatic volcano. Bull Volcanol 52(1):28–48. doi:10.1007/BF00641385

  20. Junqueira-Brod TCC, Brod JA, Thompson RN, Gibson SA (1999) Spinning droplets—a conspicuous lapilli-size structure in kamafugitic diatremes of Southern Goiás, Brazil. Brazilian Journal of Geology 29(3):437–440

  21. Keating GN, Valentine GA, Krier DJ, Perry FV (2008) Shallow plumbing systems for small-volume basaltic volcanoes. Bull Volcanol 70(5):563–582. doi:10.1007/s00445-007-0154-1

  22. Khitarov NI, Lebedev EB, Dorfman AM, Bagdasarov NS (1979) Effect of temperature, pressure and volatile components upon the surface-tension of basaltic melt. Geokhimiya 10:1427–1438. doi:10.1134/S1087659612010130

  23. Klein FW, Koyanagi RY, Nakata JS, Tanigawa WR (1987) The seismicity of Kilauea's magma system, in: Derek TW, Wright TL, Stauffer PH (Eds.) Volcanis in Hawaii. U.S. Geol Surv Prof Pap, 1350(2), pp. 1019–1185

  24. Kress VC, Carmichael IS (1991) The compressibility of silicate liquids containing Fe2O3 and the effect of composition, temperature, oxygen fugacity and pressure on their redox states. Contrib Mineral Petrol 108(1–2):82–92. doi:10.1007/BF00307328

  25. Lange RA, Carmichael IS (1987) Densities of Na2O-K2O-MgO-MgO-FeO-Fe2O3-Al3O3-TiO2-SiO2 liquids: new measurements and derived partial molar properties. Geochimica et Cosmochimica Acta 51(11):2931–2946. doi:10.106/0016–7037(87)90368–1

  26. Lister JR, Kerr RC (1991) Fluid-mechanical models of crack propagation and their application to magma transport in dykes. Journal of Geophysical Research: Solid Earth 96(B6):10049–10077. doi:10.1029/91JB00600

  27. Mader HM, Llewellin EW, Mueller SP (2013) The rheology of two-phase magmas: a review and analysis. J Volcanol Geotherm Res 257:135–158. doi:10.1016/j.jvolgeores.2013.02.014

  28. Mattsson HB (2012) Rapid magma ascent and short eruption durations in the Lake Natron–Engaruka monogenetic volcanic field (Tanzania): a case study of the olivine melilititic Pello Hill scoria cone. J Volcanol Geotherm Res 247:16–25. doi:10.1016/j.jvolgeores.2012.07.009

  29. McClintock M, White JDL, Houghton BF, Skilling IP (2008) Physical volcanology of a large crater-complex formed during the initial stages of Karoo flood basalt volcanism, Sterkspruit, Eastern Cape, South Africa. J Volcanol Geotherm Res 172(1):93–111. doi:10.1016/j.jvolgeores.2005.11.012

  30. Mcdonald GA (1972) Volcanoes. Prentice-Hall Inc.

  31. Médard E, Grove TL (2008) The effect of H2O on the olivine liquidus of basaltic melts: experiments and thermodynamic models. Contrib Mineral Petrol 155(4):417–432. doi:10.1007/s00410-007-0250-4

  32. Misiti V, Vetere F, Mangiacapra A, Behrens H, Cavallo A, Scarlato P, Dingwell DB (2009) Viscosity of high-K basalt from the 5th April 2003 Stromboli paroxysmal explosion. Chem Geol 260(3):278–285. doi:10.1016/j.chemgeo.2008.12.023

  33. Mollo S, Putirka K, Misiti V, Soligo M, Scarlato P (2013) A new test for equilibrium based on clinopyroxene–melt pairs: clues on the solidification temperatures of Etnean alkaline melts at post-eruptive conditions. Chem Geol 352:92–100. doi:10.1016/j.chemgeo.2013.05.026

  34. Mollo S, Giacomoni PP, Andronico D, Scarlato P (2015) Clinopyroxene and titanomagnetite cation redistributions at Mt. Etna volcano (Sicily, Italy): footprints of the final solidification history of lava fountains and lava flows. Chem Geol 406:45–54. doi:10.1016/j.chemgeo.2015.04.017

  35. Namur O, Charlier B, Toplis M, Vander Auwera J (2011) Prediction of plagioclase-melt equilibria in anhydrous silicate melts at 1-atm. Contribution to Mineralogy and Petrology 163:133–150. doi: 10.1007/s00410-011-0662-z

  36. Perinelli C, Mollo S, Gaeta M, De Cristofaro SP, Palladino DM, Armienti P, Scarlato P, Putirka KD (2016) An improved clinopyroxene-based hygrometer for Etnean magmas and implications for eruption triggering mechanisms. American Mineralogist, in press. doi:10.2138/am-2016-5916

  37. Pioli L, Azzopardi BJ, Cashman KV (2009) Controls on the explosivity of scoria cone eruptions: Magma segregation at conduit junctions. J Volcanol Geotherm Res 186(3):407–415.

  38. Pioro I, Morky S (2011) Thermophysical properties at critical and supercritical pressures. In: Belmiloudi A (ed) Heat transfer - theoretical analysis, experimental investigations and industrial systems. doi:10.5772/13790

  39. Putirka KD (2005) Igneous thermometers and barometers based on plagioclase + liquid equilibria: tests of some existing models and new calibrations. Am Mineral 90(2–3):336–346. doi:10.2138/am.2005.1449

  40. Putirka KD (2008) Thermometers and barometers for volcanic systems. Rev Mineral Geochem 69(1):61–120. doi:10.2138/rmg.2008.69.3

  41. Reynolds P, Brown RJ, Thordarson T, Llewellin EW (2016) The architecture and shallow conduits of Laki-type pyroclastic cones: insights into a basaltic fissure eruption. Bull Volcanol 78(5):1–18. doi:10.1007/s00445-016-1029-0

  42. Roeder PL, Emslie R (1970) Olivine-liquid equilibrium. Contrib Mineral Petrol 29(4):275–289. doi:10.1007/BF00371276

  43. Rosseel JB, White JDL, Houghton BF (2006) Complex bombs of phreatomagmatic eruptions: role of agglomeration and welding in vents of the 1886 Rotomahana eruption, Tarawera, New Zealand. Journal of Geophysical Research: Solid Earth 111:B12. doi:10.1029/2005JB004073

  44. Ruth DCS, Calder ES (2014) Plate tephra: preserved bubble walls from large slug bursts during violent Strombolian eruptions. Geology 42:11–14. doi:10.1130/G34859.1

  45. Rutherford MJ (2008) Magma ascent rates. Rev Mineral Geochem 69:241–271

  46. Sánchez MC, Sarrionandia F, Arostegui J, Larrondo E, Ibarguchi JG (2009) Development of spheroidal composite bombs by welding of juvenile spinning and isotropic droplets inside a mafic eruption column. J Volcanol Geotherm Res 186(3):265–279. doi:10.1016/j.jvolgeores.2009.07.005

  47. Schmincke HU, Sumita M (2010) Geological evolution of the Canary Islands. A young volcanic archipelago adjacent to the old African continent. Gorres-Druckerei und Verlag gmbh, Koblenz

  48. Shea T, Houghton BF, Gurioli L, Cashman KV, Hammer JE, Hobden BJ (2010) Textural studies of vesicles in volcanic rocks: an integrated methodology. J Volcanol Geotherm Res 190(3):271–289. doi:10.1016/j.jvolgeores.2009.12.003

  49. Shea T, Gurioli L, Houghton BF, Cioni R, Cashman KV (2011) Column collapse and generation of pyroclastic density currents during the A.D. 79 eruption of Vesuvius: the role of pyroclast density. Geology 39:695–698. doi:10.1130/G32092.1

  50. Shin H, Lindquist WB, Sahagian DL, Song SR (2005) Analysis of the vesicular structure of basalts. Comput Geosci 31(4):473–487

  51. Sottili G, Taddeucci J, Palladino DM (2010) Constraints on magma–wall rock thermal interaction during explosive eruptions from textural analysis of cored bombs. J Volcanol Geotherm Res 192(1):27–34

  52. Sparks RSJ, Baker L, Brown RJ, Field M, Schumacher J, Stripp G, Walters A (2006) Dynamical constraints on kimberlite volcanism. J Volcanol Geotherm Res 155(1):18–48. doi:10.1016/j.jvolgeores.2006.02.010

  53. Toramaru A (2006) BND (bubble number density) decompression rate meter for explosive volcanic eruptions. J Volcanol Geotherm Res 154(3):303–316. doi:10.1016/j.jvolgeores.2006.03.027

  54. Ushioda M, Takahashi E, Hamada M, Suzuki T (2014) Water content in arc basaltic magma in the Northeast Japan and Izu arcs: an estimate from Ca/Na partitioning between plagioclase and melt. Earth, Planets and Space 66(1):1–10. doi:10.1186/1880-5981-66-127

  55. Walker GP (2000) Basaltic volcanoes and volcanic systems. In: Sigurdsson H, Houghton B, McNutt S, Rymer H, Stix J (eds) The encyclopedia of volcanoes, first edn. Academic Press, San Diego, pp 283–289

  56. Wilson L, Head JW III (2007) An integrated model of kimberlite ascent and eruption. Nature 447:53–57

Download references


Part of this work was supported by MIUR project - Premiale NORTh (New hORizons of the Technology applied to experimental researches and geophysical and volcanological monitoring, P.I. P. Scarlato). We are grateful to A. Rizzo (INGV-Palermo) for assistance in the field and for covering the costs of bulk rock analysis. P. Scarlato and M. Nazzari are also acknowledged for logistic support and assistance in the use of the micro-analytical facilities of HPHT laboratory of INGV - Rome. The sampling campaign has been carried out in January–February 2015 in the framework of a field trip organized with OVSICORI and ICE. The editor J.D.L. White, L. Gurioli, and an anonymous reviewer provided valuable comments and constructive suggestions that greatly improved the quality of the work.

Author information

Correspondence to Andrea Di Piazza.

Additional information

Editorial responsibility: J.D.L. White

Electronic supplementary material

Figure S1

(DOCX 892 kb)

Table S1

(XLSX 35 kb)

Table S2

(XLS 77 kb)

Table S3

(XLS 47 kb)

Table S4

(XLS 60 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Di Piazza, A., Del Bello, E., Mollo, S. et al. Like a cannonball: origin of dense spherical basaltic ejecta. Bull Volcanol 79, 37 (2017).

Download citation


  • Cannonballs
  • Basaltic explosive eruptions
  • Scoria cones
  • Monogenic volcanoes
  • Magma ascent rate