Michael Ort

School of Earth and Sustainability

PO Box 4099

Northern Arizona University

Flagstaff, AZ, 86011 USA



I am a professor within the SES and teach both geology and environmental sciences courses.

My research, which is described in more detail below, focuses on volcanoes. I am particularly interested in a) human adaptations to cinder-cone eruptions, b) phreatomagmatic processes (explosive water/magma interactions), c) pyroclastic flows and eruptions, d) environmental effects of eruptions, including chemical cycling, and e) crustal ascent processes (mostly using petrology and geochemistry as tools).

I am also the sciences and engineering faculty coordinator for the Interdisciplinary Global Programs, in which students complete two majors (a science/engineering degree and a language/culture degree) and spend a year abroad studying in their new language.




I teach courses in both Environmental Sciences and Geology.

Environmental Sciences

Generally, I teach ENV 385W, Energy, Resources, and Policy, and ENV 360, Chemistry and Physics of the Environment. Over the years, I have taught most of the environmental sciences courses at least once.


In Geology, I teach undergraduate courses in Physical Geology (GLG 101), Field Mapping (GLG 240 and 440), and Igneous and Metamorphic Petrology (GLG 315), as well as graduate courses in Volcanology and Igneous Petrology (GLG 520 and 612).




My research interests are diverse, but center on volcanoes.


I study volcanoes, with particular interest in the processes of pyroclastic currents and in magmatic processes in the crust. This work often involves careful fieldwork, paleomagnetism, and geochemistry.  My goals are to better understand explosive processes at volcanoes so that we can better protect the public from volcanic hazards.


I have several ongoing projects:


Hopi Buttes (Tsezhin Bi'i) of NE Arizona: These are nephelinitic/monchiquitic (weirdo rocks!) volcanoes that formed maars, tuff rings, and tuff cones, as well as some spatter cones. The area was the site of a large playa in Miocene time, and the volcanoes erupted through saturated sediments. The exposures are fantastic, and my graduate students and I are investigating the phreatomagmatic eruption processes and sedimentary history of the area. Facies analysis allows us to determine how the pyroclastic currents changed character out from the vent, while vent facies analysis allows us to understand the processes of magma-water interaction better. Anisotropy of magnetic susceptibility studies are helping us determine the depositional processes from the surges. I would like to work with other students on processes of water-magma interactions, flow processes, and petrology at the Hopi Buttes. Water-magma interactions are very common, but we do not understand why they occur in some eruptions but not in others, even at the same volcano. We need to understand how magma and water interact explosively in order to be able to define hazards. I currently have a NASA grant, with Lauren Edgar at the USGS in Flagstaff, to study duneforms in the deposits from maar volcanoes.  An MS student, Ben Wheeler, is studying these bedforms in the Hopi Buttes and Zuni Salt Lake.


Mexico: I work with Gerardo Carrasco-NúĖez on several Recent maar volcanoes in the Serdán-Oriental basin in the eastern part of the Central Volcanic Belt of Mexico. We have been studying vent migrations at several maars, including Tecuitlapa and Atexcac. My student, Allison Austin, studied a rhyolitic maar, Tepexitl, in great detail and then extended her study of rhyolite/water interaction processes while on a Fulbright scholarship in Germany. She worked with Bernd Zimanowski carrying out explosion simulations using “magmas” from Tepexitl.


San Francisco volcanic field around Flagstaff: I am working with archaeologists and geomorphologists on a project studying the impact of the ~900 y.b.p. of Sunset Crater on the people living here at that time. This project has expanded to studying the interactions of humans and volcanoes at other very young scoria cones in southwestern North America, including Little Springs, Paricutin, and Jorullo. Scoria cones are relatively small volcanoes that affect limited areas, but we have found that, because they commonly form where people are living, their effects on humans can be significant. We have found evidence of human interactions with the eruptions themselves (offerings of corn and ceramic sherds), use of the lava flows for defensive purposes and caching water, as well as evidence of changes in agricultural practices in adaptation to the eruptions. I just finished an NSF-funded project to study the eruption dynamics of Sunset Crater, a scoria cone that formed in a violent Strombolian eruption about 1085 CE. One MS student, Karl Wagner, worked with me on this project, as well as a post-doctoral researcher at ASU, Fabrizio Alfano.  Emily Anderson, an MS student working with me, studied how water gains access to magma in phreatomagmatic eruptions, using a geothermal modeling program to study two phreatomagmatic eruptions in the San Francisco volcanic field.


Italy: In addition, I have been working in the Campi Flegrei area of southern Italy for a number of years, studying the pyroclastic deposits associated with the ~39 ka Campanian Ignimbrite/Museo Breccia/Piperno Tuff eruption. I have a new NSF grant to fund work on thesource of the gas in the Campanian Ignimbrite.  This work is in collaboration with Victoria Smith at Oxford University, Guido Giordano at Universita di Roma Tre, and Roberto Isaia at Osservatorio Vesuviano.  This project has funding for several MS students to work on stratigraphic and geochemical projects.


My colleagues, Paul Sheppard (dendrochronologist at University of Arizona) and Mark Elson (Desert Archaeology) and I have been developing a new way of dating young tephra-producing eruptions. We are analyzing the chemical changes in tree rings caused by eruptions. We are finding that trees take in different chemicals when their roots are covered by tephra, and we can detect this using the ICP-MS at NAU. This technique appears to work well with cinder cones.


Recent Publications


I can send pdfs of many of these papers upon request. I also have several manuscripts submitted, so those may be available soon.


Ort, M.H., Best, J.A., Cashman, K.V., Di Muro, A., Rosi, M., Mothes, P.A., Hall, M.L., submitted, Conduit processes during short-lived hiatuses in violent eruptions: the double-barreled 800 yBP eruption at Quilotoa Volcano, Ecuador; Geological Society of America Bulletin, 30 p., 13 figures.

Alfano, F., Ort, M.H., Pioli, L., Self, S., Hanson, S., Clarke, A.B., Roggensack, K., Allison, C.M., Amos, R., in press, The sub-Plinian monogenetic basaltic eruption of Sunset Crater, Arizona, USA; Geological Society of America Bulletin, 36 p., 9 figures.

Elson, M.D., Ort, M.H., Sheppard, P.R., Samples, T.L., Anderson, K.C., May, E.M., in press, A.D. 1064 No More? A multidisciplinary re-evaluation of the date of the eruption of Sunset Crater volcano, northern Arizona; University of Utah Press, 68 p. 7 figures, 3 tables.

Elson, M.D., Ort, M.H., 2018, Archaeological volcanology; in Encyclopedia of Archaeological Sciences, S.L. López Varela (ed.), John Wiley & Sons, Inc., 5 p., DOI: 10.1002/9781119188230.saseas0041

Ort, M.H., Lefebvre, N.S., Neal, C.A., McConnell, V.S., Wohletz, K.H., 2018, Linking the Ukinrek 1977 maar-eruption observations to the tephra deposits: new insights into maar depositional processes; Journal of Volcanology and Geothermal Resources, v. 360, 36-60, doi 10.1016/j.jvolgeores.2018.07.005.

van Otterloo, J., Ort, M.H., Cruden, A.R., 2018, Unique occurrence of a folded in-vent dike: New insights on magma-water mixing; Geology, v. 46, p. 379-382, doi.org/10.1130/G39794.1

Re, G., White, J.D.L., Muirhead, J.D., Ort, M.H., 2016, Subterranean fragmentation of magma during conduit initiation and evolution in the shallow plumbing system of the small-volume Jagged Rocks volcanoes (Hopi Buttes Volcanic Field, Arizona, USA); Bulletin of Volcanology, v. 78:55, DOI 10.1007/s00445-016-1050-3.

Elson, M.D., Ort, M.H., Anderson, K.C., 2016, Sunset Crater and Little Springs Volcano eruptions: Disaster management in the Eleventh-century A.D. Southwest; in Herhahn, C.L., and Ramenofsky, A.F. (eds.), Exploring Cause and Explanation: Historical Ecology, Demography, and Movement in the American Southwest, University of Colorado Press, Boulder, p. 47-72.

Muirhead, J.D., Van Eaton. A.R., Re, G. White, J.D.L, Ort, M.H., 2016, Monogenetic volcanoes fed by interconnected dikes and sills in the Hopi Buttes volcanic field, Navajo Nation, USA, Bulletin of Volcanology, v. 78:11, p. 1-16.

Ort, M.H., Di Muro, A., Michon, L., BachŹlery, P., 2016, Explosive eruptions from the interaction of magmatic and hydrothermal systems during flank extension: The Bellecombe Ashes of Piton de La Fournaise (La Réunion Island), Bulletin of Volcanology, v. 78, p. 1-14.

Unema, J.A., Ort, M.H., Larsen, J.F., Neal, C.A. Schaefer, J.R., 2016, Water-magma interaction and plume processes in the 2008 Okmok eruption, Geological Society of America Bulletin, v. 128, p. 792-806.

Soriano, C., Beamud, E., Garcés, M., Ort, M.H., 2015, ‘Anomalous’ magnetic fabrics of dikes in the stable single domain/superparamagnetic threshold, Geophysical Journal International, v. 204 (2):1040-1059.

Re, G., White, J.D.L., Ort, M.H., 2015, Dikes, sills, and stress-regime evolution during emplacement of the Jagged Rocks Complex, Hopi Buttes Volcanic Field, Navajo Nation, USA, Journal of Volcanology and Geothermal Research, v. 295, p. 65-79, doi: 10.1016/j.jvolgeores.2015.01.009.

Ort, M.H., Porreca, M., Geissman, J.W., 2015, Introduction to The use of palaeomagnetism and rock magnetism to understand volcanic processes: in Ort, M.H., Porreca, M. & Geissman, J.W. (eds) The use of palaeomagnetism and rock magnetism to understand volcanic processes. Geological Society, London, Special Publications, 396, p. 1-11, http://dx.doi.org/10.1144/SP396.17.

Ort, M.H., Newkirk, T.N., Vilas, J.F., Vazquez, J.A., 2015, Towards the definition of AMS facies in the deposits of pyroclastic density currents: in Ort, M.H., Porreca, M. & Geissman, J.W. (eds) The use of palaeomagnetism and rock magnetism to understand volcanic processes. Geological Society, London, Special Publications, 396, p. 205-226, http://dx.doi.org/10.1144/SP396.8.

Ort, M.H., de Silva, S.L., Jiménez C., N., Jicha, B.R., Singer, B.S., 2013, Correlation of ignimbrites using characteristic remanent magnetism and anisotropy of magnetic susceptibility, central Andes, Bolivia; Geochemistry, Geophysics, Geosystems, v. 14, p. 141-157, doi: 10.1029/2012GC004276.

Elson, M.D., Ort, M.H., 2012, Fire in the sky: The eruption of Sunset Crater Volcano, in Downum, C., ed., Hisatsinom: Ancient peoples in a land without water. School for Advanced Research, Santa Fe, p. 26-33.

Elson, M.D., Ort, M,H., Anderson, K.C., Heidke, J.M., Sheppard, P.R., and Samples T.L., 2011, In the shadow of the volcano: Prehistoric settlement in the U.S. 89 Project Area. In M.D. Elson (ed.) Sunset Crater Archaeology: The history of a volcanic landscape. Prehistoric settlement in the shadow of the volcano, Anthropological Papers No. 37, Center for Desert Archaeology, Tucson, p. 187-211. 

Elson, M.D., Ort, M.H., Sheppard, P.R., Samples, T.L., Anderson, K.C., May, E.M., and Street, D.J., 2011, Sunset Crater Volcano. In M.D. Elson (ed.) Sunset crater archaeology: The history of a volcanic landscape. Prehistoric settlement in the shadow of the volcano, Anthropological Papers No. 37, Center for Desert Archaeology, Tucson, p. 103-129.

Salisbury, M.J., Jicha, B.R., de Silva, S.L., Singer, B.S., Jiménez-C., N., Ort, M.H., 2011, 40Ar/39Ar chronostratigraphy of Altiplano-Puna Volcanic Complex ignimbrites reveals the development of a major silicic magmatic province; Geological Society of America Bulletin, v. 123, p. 821–840, doi: 10.1130/B30280.1.

Austin-Erickson, A., Ort, M.H., Carrasco-NúĖez, G., 2011, Rhyolitic phreatomagmatism explored: Tepexitl Tuff Ring (Eastern Mexican Volcanic Belt), Journal of Volcanology and Geothermal Research, v. 201, p. 325-341.

Sheppard, P.R., May, E.M., Ort, M.H., Anderson, K.C., Elson, M.D., 2010, Dendrochronological responses to a tornado. in Stoffel, M.,  Bollschweiler, M., Butler, D.R., Luckman, B.H. (eds.), Tree-Ring  analysis in natural hazards research: A state-of-the-art, Advances in  Global Change Research 41, Springer: Heidelberg, London, New York, p. 305–307.

Sheppard, P.R., Ort, M.H., Anderson, K,C., Clynne, M.A., May, E.M., 2009, Multiple dendrochronological responses to the eruption of Cinder Cone, Lassen Volcanic National Park, California, Dendrochronologia, v. 27, p. 213-221.    

Ort, M.H., Carrasco-NúĖez, G., 2009, Lateral vent migration during phreatomagmatic and magmatic eruptions at Tecuitlapa Maar, east-central Mexico, Journal of Volcanology and Geothermal Research, v. 181, p. 67-77, doi:10.1016/j.jvolgeores.2009.01.003.

Sheppard, P.R., Ort, M.H., Anderson, K.C., Elson, M.D., Vázquez-Selem, L., Clemens, A.W., Little, N.C., and Speakman, R.J. 2008. Multiple dendrochronological signals indicate the eruption of Parícutin Volcano, Michoacán, Mexico. Tree-Ring Research 64(2):97-108.

Austin-Erickson, A., Büttner, R., Dellino, P., Ort, M.H., and Zimanowski, B., 2008, Phreatomagmatic explosions of rhyolitic magma: Experimental and field evidence, Journal of Geophysical Research, 113, B11201, doi:10.1029/2008JB005731.

Ort, M.H., Elson, M.D., Anderson, K.C., Duffield, W.A., and Samples, T.L., 2008, Variable effects of cinder-cone eruptions on prehistoric agrarian human populations in the American Southwest, Journal of Volcanology and Geothermal Research, v. 176, p. 363-376.

Pioli, L., Lanza, R., Ort, M.H., Rosi, M., 2008, Magnetic fabric, welding texture and strain fabric in the Nuraxi tuff, Sardinia, Italy, Bulletin of Volcanology, v. 70, p. 1123-1137.

Ort, M.H., Elson, M.D., Anderson, K.C., Duffield, W.A., Hooten, J.A., Champion, D.E., and Waring, G., 2008, Effects of scoria-cone eruptions upon nearby human communities, Geological Society of America Bulletin, v. 120, p. 476-486.

Hooten, J.A., Ort, M.H., and Elson, M.D., 2007, Chapter 6. The origin of cinders in Wupatki National Monument, in Elson, M.D., [ed.], Sunset Crater archaeology: The history of a volcanic landscape.  Environmental analyses, Anthropological Papers No. 33, Center for Desert Archaeology, Tucson, p. 77-85.

Hooten, J.A., and Ort, M.H., 2007, Chapter 7. Sunset Crater tephra mapping project: The creation of an isopach map, in Elson, M.D., [ed.], Sunset Crater archaeology: The history of a volcanic landscape.  Environmental analyses, Anthropological Papers No. 33, Center for Desert Archaeology, Tucson, p. 87-93.

Ort, M.H., Elson, M.D., and Champion, D.E., 2007, Chapter 8. A paleomagnetic dating study of Sunset Crater, in Elson, M.D., [ed.], Sunset Crater archaeology: The history of a volcanic landscape.  Environmental analyses, Anthropological Papers No. 33, Center for Desert Archaeology, Tucson, p. 95-102.

Elson, M. D., Ort, M.H., Anderson, K.A., and Heidke, J.M., 2007, Living with the volcano: the 11th century A.D. eruption of Sunset Crater. In Living under the shadow: Cultural impacts of volcanic eruptions: Walnut Creek, Left Coast Press, p. 107–132.

Carrasco-NuĖez, G., Ort, M.H., and Romero, C., 2007, Anatomy of a maar volcano: Case study of Atexcac crater, eastern Mexico; Journal of Volcanology and Geothermal Research, v. 159, p. 179-197.

Elson, M.D., Ort, M.H., and Philips, B.G., 2006, Environmental Setting, in Elson, M.D., [ed.], Sunset Crater Archaeology: The history of a volcanic landscape. Introduction and site descriptions, Anthropological Papers No. 30, part 1, Center for Desert Archaeology, Tucson, p. 17-42.

Vazquez, J.A., and Ort, M.H., 2006, Facies variation of eruption units produced by the passage of single pyroclastic surge currents, Hopi Buttes volcanic field, USA; Journal of Volcanology and Geothermal Research, 154:222–236.

Duffield, W., Riggs, N., Kaufman, D., Champion, D., Fenton, C., Forman, S., McIntosh, W., Hereford, R., Plescia, J., and Ort, M., 2006, Multiple constraints on the age of a Pleistocene lava dam across the Little Colorado River at Grand Falls, Arizona; Geological Society of America Bulletin, 118:421-429.

Ort, M.H., Anderson, D.E., and Ostergren, D.M., 2006, Integrating Policy and Land Management Issues into a Natural Sciences Education: Teaching Environmental Sciences on the lower San Juan River, Utah, Journal of Geoscience Education, v. 53, p. 116-122.

Sheppard, P.R., May, E.M., Ort, M.H., Anderson, K.C., Elson, M.D., 2005, Dendrochronological responses to the 24 October 1992 tornado at Sunset Crater, northern Arizona; Canadian Journal of Forest Research, 35:2911-2919.



Paleomagnetism Laboratory

I have a spinner magnetometer and an AF demagnetizer, which my students and I use for standard paleomagnetic studies and secular variation studies of volcanic deposits, which is especially useful for dating young volcanic units. Currently, we are dating some Holocene flows in the Southwestern USA using secular variation. I also have an AGICO Kappabridge KLY-4 on long-term loan that we use for anisotropy of magnetic susceptibility studies. I have a student studying the emplacement dynamics in a dike complex in the Hopi Buttes using this technique and several undergraduate students have carried out theses using this instrument.


Other Laboratories

The department has a well-equipped particle-size analysis laboratory. A scanning electron microscope allows us to study features of minerals and volcanic shards. My students and I use it for grain shape analysis. We have access to several ICP-MS instruments, including an MC-ICP-MS and quadrupole, with laser, and the sample-preparation laboratories that go with them.


Some Related Pages:

Several other professors do volcano-related work at NAU:

Nancy Riggs, Professor, is a volcanologist. http://jan.ucc.nau.edu/~nrr/nrr.html

Jim Wittke, Supervisor, Microprobe Lab: http://oak.ucc.nau.edu/wittke/


The home page, where you can find information on the academic programs, is



created by Michael Ort, michael.ort(at)nau.edu


URL: http://jan.ucc.nau.edu/~mho