Oregon State University

College of Earth, Ocean, and Atmospheric Sciences

Directory of People

Shanaka (Shan) de Silva

Shanaka de Silva photo
Discipline: Geology and Geophysics
Office: Wilkinson 216
Phone: 541-737-1212
Fax: 541-737-1200
Email: desilvas@geo.oregonstate.edu


Volcanology, Igneous Petrology, Planetary Surface Processes (aeolian sedimentology/geomorphology)

Research Interests

I am a field-based volcanologist. The questions I address start in the field – Nature is intriguing, and there are many things that make me go… “hmmm….now that is interesting” or “that doesn't fit what we know”, or simply “wow, that is really cool, lets find out more about this”. There are some core themes to my research. Projects my students and I are currently working on emphasize magmatism and volcanism in volcanic arcs, physical volcanology and petrology of explosive volcanic eruptions, effusion of crystal–rich lava, caldera (super)volcanism and the volcano-plutonic connection. To address these I use the volcanologists toolbox (Petrology, Geochemistry, Physical Volcanology, Geochronology, Remotely Sensed data, Geophysics) at all different scales. I am not an “expert” in any particular analytical technique, but I look for different tools and creative solutions for the problems of interest often collaboration with those who are experts. I like to think of this as "Volcano Forensics" - a CSI approach to volcanology.

Our research projects have taken us to Chile, Peru, Argentina, Bolivia, Italy, Indonesia, China, and Japan. Read about our work at Lake Toba, a large caldera in Sumatra.

I am also interested in Aeolian geomorphology. Why? While studying volcanic features in the high Andes, we couldn't ignore the fact that wind was producing an other-world landscape that was a valuable analog for the surface of Mars. Starting with yardangs, we have begun to address how the wind erodes and modifies high desert volcanic terrains. Our latest work is trying to understand how gravel dominated bedforms form and rates of aeolian erosion of ignimbrite.

The broader impacts of our work relate to volcanic hazards, planetary surface processes, volcanism and climate, and Earth Science Education and Outreach (Visit our VolcanoWorld website). I am also committed to undergraduate research and Increasing Diversity in Earth Sciences.


B.Sc (Hons) Geology, University of Southampton, United Kingdom, 1982
PhD Earth Sciences, Open University, United Kingdom, 1987


GEO 409 – Contemporary Issues in Earth Science (Spring annually)
GEO 495 – Field Camp (Summer 2014, 2016)
GEO 627 – Advanced Volcanology (Fall 2014)
GEO 201 – Physical Geology (Winter annually)

Graduate Students

Current Graduate Students

  • Adonara Mucek (BS U of Hawaii, 2012) Resurgence at Toba Caldera, Sumatra (PhD)
  • Michelle Neely (BS Portland State, 2014) Pattern to Process:morphometry and process in gravel megaripples in the Puna of Argentina

Recent Graduate Theses (Primary Advisor unless stated)

  • Bethany Murphy (MS 2015) Timescales of silicic magmatic processes:U-Series zircon chronochemistry of Mt Unzen, Japan
  • Stephanie Grocke (PhD 2014) Magma Dynamics and Evolution in Continental Arcs: Insights form the Central Andes
  • Dale Burns (PhD 2014) Crustal Architecture and Magma Dynamics in a Large Continental Magmatic System: A Case Study of the Purico-Chascon Volcanic Complex, Northern Chile
  • Jason Kaiser (PhD 2014) Understanding Large Resurgent Calderas and Associated Magma Systems: The Pastos Grandes Caldera Complex, Southwest Bolivia
  • Jamie Kern (MS 2012) The plutonic record of the Altiplano Puna Volcanic Complex revealed by zircon chronology
  • Rodrigo Iriarte (MS 2012) The Cerro Guacha Caldera Complex, SW Bolivia: stratigraphy, volcanology, and magma dynamics
  • Claire McLeod (Ph.D 2012) Investigations of crustal contamination through petrology and geochemistry (U of Durham Co-advised w/ Jon Davidson)
  • Casey Tierney (MS 2011) Timescales of silicic magmatic processes: U-Series chronochemistry of effusive domes of the Altiplano Puna Volcanic Complex.
  • Chris Folkes (Ph.D. 2011) Physical Volcanology and Magmatic evolution of the Cerro Galan Caldera Complex, NW Argentina. (Monash University, Co-advisor w/Ray Cas, Heather Wright)
  • Chris Harpel (Ph.D. 2010), Lahar sedimentology and hazards of the 2ka eruption of El Misti, southern Peru
  • Robert Peckyno (MS - 2010), Morphometric parameters of terrestrial lavas
  • Mangon Abot (MS - 2010), Amphibole-Plagioclase P-T estimates for the Altiplano Puna Volcaninc Complex (Co-advisor with Anita Grunder)

Former Advisees and Co-Advisees – where are they now?

  • Stephanie Grocke, Smithsonian Institution, Post Doctoral Fellow
  • Dale Burns, University of Iowa, Research Faculty
  • Jason Kaiser, University of Southern Utah, Assistant Professor
  • Chris Folkes, Geoscience Australia, Geologist
  • Rodrigo Iriarte , Universidad Major San Andres, La Paz, Bolivia, Professor
  • Jamie Kern, Training Horses, New Zealand
  • Claire McLeod, University of Houston, Research Associate
  • Casey Tierney, PhD program, Northern Arizona University
  • Chris Harpel, VDAP, USGS, CVO Vancouver, WA
  • Robert Peckyno, Multimedia Artist/Program Support, Corvallis
  • Mangon Abot, Malaysian Geological Survey, Program Head

Recent Post docs / Research Visitors

  • Akihiko Tomiya (2014-2015) Institute of Earthquake and Volcano Geology, Geological Survey of Japan
  • Bo Pan - (2013 - 2014) Chinese Earthquake Administration
  • Mauro Spagnuolo (2013 - 2014) - CONICET Research Fellow at Universidad Buenos Aires, Argentina
  • Trish Gregg (2010 - 2014) - Assistant Professor at University of Illinois, Urbana-Champaign


Selected Papers from last Five Years (Student authors identified with #; Post docs )

  1. Gregg, P. M., Grosfils, E. B., & de Silva, S. L. (2015). Catastrophic caldera-forming eruptions II: The subordinate role of magma buoyancy as an eruption trigger. Journal of Volcanology and Geothermal Research, 305(C), 100–113. http://doi.org/10.1016/j.jvolgeores.2015.09.022
  2. Perkins, J. P#., Finnegan, N. J., & de Silva, S. L. (2015). Amplification of bedrock canyon incision by wind. Nature Geoscience. doi:10.1038/ngeo2381
  3. de Silva, S. L., Mucek, A. E.#, Gregg, P. M., & Pratomo, I. (2015). Resurgent Toba—field, chronologic, and model constraints on time scales and mechanisms of resurgence at large calderas. Frontiers in Earth Science, 3. doi:10.3389/feart.2015.00025
  4. Burns, D. H. #, de Silva, S. L., Tepley, F., III, Schmitt, A. K., & Loewen, M. W.# (2015). Earth and Planetary Science Letters. Earth and Planetary Science Letters, 422(C), 75–86. doi:10.1016/j.epsl.2015.04.002
  5. de Silva, S. L., Riggs, N. R., & Barth, A. P. (2015). Quickening the Pulse: Fractal Tempos in Continental Arc Magmatism. Elements, 11(2), 113–118. doi:10.2113/gselements.11.2.113
  6. de Silva, S.L. and Gregg, P.M., (2014) Thermomechanical feedbacks in magmatic systems: The critical importance of the thermal history of host rocks to the growth, longevity, and evolution of large silicic magma reservoirs. Journal of Volcanology and Geothermal Research 282(C), 77–91. doi: 10.1016/j.jvolgeores.2014.06.001
  7. Breitkreuz, C., de Silva, S. L., Wilke, H. G., Pfänder, J. A., & Renno, A. D. (2014). Neogene to Quaternary ash deposits in the Coastal Cordillera in northern Chile: Distal ashes from supereruptions in the Central Andes. Journal of Volcanology and Geothermal Research, 269, 68–82. doi:10.1016/j.jvolgeores.2013.11.001
  8. Gregg, P. M., de Silva, S. L., & Grosfils, E. B. (2013). Thermomechanics of shallow magma chamber pressurization: Implications for the assessment of ground deformation data at active volcanoes. Earth and Planetary Science Letters, 384(C), 100–108. doi:10.1016/j.epsl.2013.09.040
  9. de Silva, S. L., Spagnuolo, M. G., Bridges, N. T., & Zimbelman, J. R. (2013). Gravel-mantled megaripples of the Argentinean Puna: A model for their origin and growth with implications for Mars. Geological Society of America Bulletin, 125(11-12), 1912–1929. doi:10.1130/B30916.1
  10. Folkes , C. B.#, de Silva, S. L., Bindeman, I. N., & Cas, R. A., 2013. Tectonic and climate history influence the geochemistry of large-volume silicic magmas: New δ 18-O data from the Central Andes with comparison to N America and Kamchatka. Journal of Volcanology and Geothermal Research. doi: 10.1016/j.jvolgeores.2013.05.014
  11. Tepley, F., de Silva, S.L., Salas, G., 2013. Magma dynamics and petrologic evolution leading to the VEI 5 2000 B.P. eruption of El Misti volcano, southern Peru. Journal of Petrology, v. 54 (10), p. 2033-2065
  12. McLeod, C.L.#, Davidson J.P., de Silva, S.L., and Schmitt, A.K., 2013. Characterizing the continental basement of the Central Andes: constraints from Bolivian crustal xenoliths. Geological Society of America Bulletin 125(5-6), 985-997. doi: 10.1130/B30721.)
  13. Ort, M. H., de Silva, S. L., Jiménez C, N., Jicha, B. R., & Singer, B. S. (2013). Correlation of ignimbrites using characteristic remanent magnetization and anisotropy of magnetic susceptibility, Central Andes, Bolivia. Geochemistry Geophysics Geosystems, 14(1), 141–157. doi:10.1029/2012GC004276
  14. Gregg, P., de Silva, S.L., Grosfils, E., and Parmigiani, 2012. Catastrophic Caldera Collapse: Models implementing temperature-dependant rheology. Journal of Volcanology and Geothermal Research, v.241-242, p.1-12, doi:10.1016/j.jvolgeores.2012.06.009
  15. Folkes, C.B.#, de Silva S.L., Schmitt, A.K., and Cas, R.A., 2011. A reconnaissance of U-Pb zircon ages in the Cerro Galán system, NW Argentina: prolonged magma residence, crystal recycling, and crustal assimilation. Journal of Volcanology and Geothermal Research, v. 206, p.136147.