Greg A. Valentine

PhD (he/him/his)

Professor Greg Valentine.

Greg A. Valentine

PhD (he/him/his)

Greg A. Valentine

PhD (he/him/his)

Director of the Center for Geohazards Studies
Professor

Specialties

Volcanic risk, phreatomagmatic explosive eruptions, basaltic volcanic fields, pyroclastic deposits, volcano fluid dynamics, volcaniclastic and surface processes

Education

PhD, Geological Sciences, University of California Santa Barbara – 1988

Research Interests

Physical processes associated with basaltic volcanism, from the scale of eruptive styles at individual volcanoes to the dynamics of basaltic fields. Interpretation of pyroclastic deposits including large-volume, widespread ignimbrites and associated calderas. Multiphase fluid dynamics and numerical modeling of explosive eruptions. Consequences of volcanic activity and spatial-temporal behavior of volcanic systems, with application to risk assessment and coupling to infrastructure response models. Evolution of volcanic landforms, particularly in arid environments.

Course Offerings

  • GLY 205 - Earth Materials
  • GLY 215 – Sedimentology
  • GLY 407/507 – Geologic Field Training (Field Camp)
  • GLY 428/528 – Geologic Hazards and Risk
  • GLY 431/531 – Volcanology
  • GLY 433/533 – Volcanic Rocks
  • GLY 578 – Advanced Field Methods
  • GLY 499 – Independent Study
  • GLY 599 – Supervised Teaching
  • GLY 633 – Graduate Research
  • GLY 700 – Thesis Guidance

Current Students

  • Meredith Cole - PhD - Caldera-forming explosive eruptions
  • Brandon Keim - PhD - Computational fluid dynamics of pyroclastic surges (Fall 2022)

Recent Former Students

  • Patrick Bobbitt - MS (2021) - Dike to vent transitions within a basaltic volcano, Horace Mesa, New Mexico
  • Claudia Fletcher - MS (2021) - Basal deposits of pyroclastic density currents: Sovana ignimbrite, Vulsini District, Italy
  • Peter Johnson – PhD (2018) – Fluid flow in disrupted porous media: volcanological and radiological waste applications.
  • Andrew Harp – PhD (2018) – The impacts of local stress fields and host rock heterogeneity on magma transport and extrusion at stratovolcanoes
  •  Matthew Sweeney – PhD (2018) – Multiphase flow in explosive volcanic eruptions: field and numerical results
  • Zachary Younger – MS (2018) – Basaltic aa lava field emplacement of the intraplate Marcath volcano (central Nevada) from field and LiDAR data 

Postdocs

  • Dr. Pranabendu Moitra - 2015 to 2017 - Experimental magma-water interaction.
  • Dr. Alison Graettinger - 2013 to 2016 - Research focus on experimental studies of phreatomagmatic explosive eruptions.

Recent Publications

Valentine GA, Ort MH, Cortés JA (2021) Quaternary basaltic volcanic fields of the American Southwest.  Geosphere, doi: 10.1130/GES02405.1 

Valentine GA, Cole MA* (2021) Explosive caldera-forming eruptions and debris-filled vents: gargle dynamics.  Geology 49:1240-1244, doi: 10.1130/G48995.1 

Valentine GA, Fierstein J, White JDL (2021) Soft sediment deformation in dry pyroclastic deposits at Ubehebe Crater. Death Valley, California.  Geology, doi:10.1130/G48147.1

Esposti Ongaro T, Cerminara M, Charbonnier SJ, Lube G, Valentine GA (2020) A framework for validation and benchmarking of pyroclastic current models.  Bulletin of Volcanology 82:51​

Moitra P, Sonder I, Valentine GA (2020) The role of external water on rapid cooling and fragmentation of magma.  Earth and Planetary Sciences 537:116194, doi:10.1016/j.epsl.2020.116194

Valentine GA (2020) Initiation of dilute and concentrated pyroclastic currents from collapsing mixtures and origin of their proximal deposits.  Bulletin of Volcanology 82:20, doi:10.1007/s00445-020-1366-x

Younger ZP, Valentine GA, Gregg TKP (2019) 'A'ā lava emplacement and the significance of rafted pyroclastic material: Marcath volcano (Nevada, USA).  Bulletin of Volcanology 81:50, doi:10.1007/200445-019-1309-6​

Valentine GA, Palladino DM, DiemKaye K, Fletcher C (2019) Lithic-rich and lithic-poor ignimbrites and their basal deposits: Sovana and Sorano formations (Latera caldera, Italy).  Bulletin of Volcanology 81:29, doi:10.1007/s00445-019-1288-7

Valentine GA, Briner JP, van Wyk de Vries B, Macorps É, Gump D (2019) 10Be exposure ages for the Late Pleistocene Gour de Tazenat maar (Chaîne des Puys volcanic field, Auvergne, France).  Quaternary Geochronology 50:8-13, doi:10.1016/j.quageo.2018.11.002

Sonder I, Harp AG, Graettinger AH, Moitra P, Valentine GA, Büttner R, Zimanowski B (2018) Meter-scale experiments on magma-water interaction.  Journal of Geophysical Research Solid Earth 123, doi:10.1029/2018JB015682

Moitra P, Sonder I, Valentine GA (2018) Effects of size and temperature-dependent thermal conductivity on the cooling of pyroclasts in air.  G3 – Geochemistry, Geophysics, Geosystems 19: doi: 10.1029/2018GC007510

Tierz P, Stefanescu ER, Sandri L, Sulpizio R, Valentine GA, Marzocchi W, Patra A (2018) Towards quantitative volcanic risk of pyroclastic density currents: probabilistic hazard curves and maps around Somma-Vesuvius (Italy).  Journal of Geophysical Research Solid Earth 123:6299-6317, doi:10.1029/2017JB015383

Sweeney MR, Grosso Z, Valentine GA (2018) Topographic controls on a phreatomagmatic maar-diatreme eruption (Holocene Dotsero volcano, Colorado, USA): field and numerical results.  Bulletin of Volcanology 80:78, doi:10.1007/s00445-018-1253-x​

Johnson, PJ, Valentine GA, Stauffer PH, Lowry CS, Sonder I, Pulgarín CC, Agudelo A (2018) Groundwater drainage from fissures as a source for lahars.  Bulletin of Volcanology 80:39, doi:10.1007/s00445-018-1214-4

Valentine GA, Sweeney MR (2018) Compressible flow phenomena at inception of lateral density currents fed by collapsing gas-particle mixtures.  Journal of Geophysical Research Solid Earth 123, doi:10.1002/2017JB015129

Harp AG, Valentine GA (2018) Emplacement controls for the basaltic-andesitic radial dikes of Summer Coon volcano and implications for flank vents at stratovolcanoes.  Bulletin of Volcanology 80: 16, doi:10.1007/s00445-018-1194-4

Graettinger AH, Valentine GA (2017) Evidence for the relative depths and energies of phreatomagmatic explosions recorded in tephra rings.  Bulletin of Volcanology 79: 88, doi:10.1007/s00445-017-1177-x

Sweeney MR, Valentine GA (2017) Impact zone dynamics of dilute mono-and polydisperse jets and their implications for initial conditions of pyroclastic density currents.  Physics of Fluids 29: 093304, doi:10.1063/1/5004197.​ 

Valentine GA, White JDL, Ross P-S, Graettinger AH, Sonder I (2017) Updates to concepts on phreatomagmatic maar-diatremes and their pyroclastic deposits.  Frontiers in Earth Science 5:68, doi:10.2289/feart.2017.00068

Amin J, Valentine GA (2017) Compound maar crater and co-eruptive scoria cone in the Lunar Crater Volcanic Field (Nevada, USA).  Journal of Volcanology and Geothermal Research 339: 41-51, doi:10.1016/jvolgeores.2017.05.002

Tadini A, Bevilacqua A, Neri A, Cioni R, Aspinall WP, Bisson M, Isaia R, Mazzarini F, Valentine GA, Vitale S, Baxter PJ, Bertagnini A, Cerminara M, De Michieli Vitturi M, Di Roberto A, Engwell S, Esposti Ongaro T, Flandoli F, Pistolesi M (2017) Assessing future vent opening locations at the Somma-Vesuvio volcanic complex: 2. Probability maps of the caldera for a future Plinian/sub-Plinian event with uncertainty quantification.  Journal of Geophysical Research 122, doi:10.1002/2016JB013858.

Valentine GA, Cortés JA, Widom E, Smith EI, Rasoazanamparany C, Johnsen R, Briner JP, Harp AG, Turrin B (2017) Lunar Crater Volcanic Field (Reveille and Pancake Ranges, Basin and Range Province, Nevada, USA).  Geosphere 13: 391-438, doi:10.1130/GES01428.1

C Bonadonna, R Cioni, A Costa, T Druitt, J Phillips, L Pioli, D Andronico, A Harris, S Scollo, O Bachmann, G Bagheri, S Biass, F Brogi, K Cashman, L Dominguez, T Durig, O Galland, G Giordano, M Gudmundsson, M Hort, A Hoskuldsson, B Houghton, JC Komorowski, U Kueppers, G La Canna, JL Le Pennec, G Macedonio, M Manga, I Manzella, M de’ Michieli Vitturi, A Neri, M Pistolesi, M Polacci, M Ripepe, E Rossi, B Scheu, R Sulpizio, B Tripoli, S Valade, GA Valentine, C Vidal, N Wallenstein (2016) MiMoVolc report on classification and dynamics of volcanic explosive eruptions.  Bulletin of Volcanology 78: 84, doi:10.1007/200445-016-1071-y.

Breard ECP, Lube G, Jones JR, Dufek J, Cronin SJ, Valentine GA, Moebis A (2016) Coupling of turbulent and non-turbulent flow regimes within pyroclastic density currents. Nature Geoscience 9: 767-771, doi:10.1038/NGEO2794

Graettinger AH, Valentine GA, Sonder I (2016) Recycling in debris-filled volcanic vents. Geology 44: 811-814, doi:10.1130/G38081.1

White JDL, Valentine GA (2016) Magmatic versus phreatomagmatic fragmentation: absence of evidence is not evidence of absence. Geosphere 12: 1478-1488, doi:10.1130/GES01337.1

Macorps É, Graettinger AH, Valentine GA, Ross P-S, White JDL, Sonder I (2016) The effects of host-substrate properties on maar-diatreme volcanoes: experimental evidence.  Bulletin of Volcanology 78:26, doi:10.1007/s00445-016-1013-8

Roche O, Buesch DC, Valentine GA (2016) Slow-moving, far-travelled dense pyroclastic flows during the Peach Spring super-eruption. Nature Communications 7: 10890, doi:10.1038/NCOMMS10890