Talking
rocks on the San Juan River, as part of the course Environmental Sciences
of the lower San Juan River
Michael Ort
School
of Earth Sciences and Environmental Sustainability
PO Box 4099
Northern Arizona University
Flagstaff, AZ, 86011 USA
928-523-9363 phone
928-523-9220 fax
http://jan.ucc.nau.edu/~mho
I am a professor within the SESES 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).
Teaching
I teach courses in both Environmental
Sciences and Geology.
Environmental Sciences: Generally, I teach ENV 385, Energy, Resources, and
Policy in the spring, and ENV 360, Chemistry and Physics of the Environment in
the fall semester. Over the years, I
have taught most of the environmental sciences courses at least once. I created the course Environmental Sciences
of the San Juan River (ENV 375) a few years ago and continue to be involved in
it.
Geology: 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).
2002
ENV 385 Resources and Policy class at Black Mesa Mine, Navajo Nation. Photo
courtesy of Dave Ostergren.
1996 Graduate Volcanology class looking
at maar deposits in the San Francisco volcanic field. Photo courtesy of
Todd Keay.
Class Home Pages
My students have access to the class home page on NAU’s
Vista site.
Research
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. Typically, this 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.
Mexico: I am
working with Gerardo Carrasco-Núñez 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.
In the 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. eruption 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, Parcutin, 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.
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 ~40 ka
Campanian Ignimbrite/Museo Breccia/Piperno Tuff eruption. There, in collaboration with
Giovanni Orsi and Mauro Rosi,
I have mostly been doing anisotropy of magnetic susceptibility studies to
determine how the currents deposited the tuffs.
We are now working on resurgence dynamics in the caldera formed by the
Monte Epomeo Green Tuff eruption about 55,000 years
ago. I also have a
collaboration with Guido Giordano and Anna Paula Vinkler
on the initiation of the Tufo Lionato
eruption of the Colli Albani outside of Rome.
Dendrochemical dating of eruptions: 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, and we are hoping to apply it to other types of volcanoes. Currently, we are attempting to date the
Sunset Crater and Cinder Cone (Lassen Volcano National Park) eruptions with
this technique. Colleen Donegan, an MS
student working with me, is applying the technique to Mount St. Helens.
Kathy Cashman, of University of Oregon, and I received NSF funding to study
the 800 BP eruption of Quilotoa volcano
in Ecuador. We are working with Patty Mothes and Jorge Bustillos of the
Instituto Geofísico in
Quito, Andrea di Muro of the Reunion Observatory, and
Mauro Rosi of the Universitá
di Pisa. It produced two large
ignimbrite-forming eruptions 800 years ago, with a several-week-long hiatus
between them. The second eruption began
by producing a few surges and then an odd,
very-crystal-rich fallout that is distributed for about 15 km radius around the
vent. How did this crystal fallout form,
and what does it tell us about the eruption dynamics?
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., de Silva, S.L., Jiménez C., N., Jicha, B.R., Singer, B.S., submitted, Correlation of
Ignimbrites Using Characteristic Remanent Magnetism and Anisotropy of Magnetic
Susceptibility, Central Andes, Bolivia; Geochemistry, Geophysics, Geosystems, 31 p text, 3 tables, 6 figures.
Elson, M.D., Ort, M.H., Anderson, K.C.,
submitted, Sunset Crater and Little Springs Volcano eruptions: Hazards management
in the 11th century A.D. prehistoric Southwest; University of
Colorado Press, 45 p text, five figures.
Valentine, G.A., Ort, M.H., Cortés, J.A.,
Hintz, A.R., submitted, Probability of basaltic eruptions in volcanic fields of
the southwestern USA – Initial hazard assessment; Geology, 12 pages, 2 tables,
1 figure, 1 dataset for repository.
Elson, M.D., Ort, M.H., and Heidke
J.M., in press, Effects
of the ca. A.D. 1100
Sunset Crater Eruption on Local
Populations, Northern Arizona. In Proceedings of the 2002 Chacmool Conference, Calgary, Alberta. University of Calgary, Alberta, Canada, 20 manuscript pages.
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-Núñez,
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., 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-Núñez, 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 Cinder Cone
Eruptions upon Nearby Human Communities, Geological Society of America
Bulletin, p. 476-486.
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-Núñez, G., Ort, M.H., and Romero, C., 2006, Anatomy
of a maar volcano: Case study of Atexcac crater, eastern Mexico; Journal of
Volcanology and Geothermal Research, v. 159, p. 179-197.
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.
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., Ort, M.H., Anderson, K., 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.
Dallegge,
T.A., Ort, M.H., McIntosh, W.C., 2003, Mio-Pliocene chronostratigraphy,
basin morphology and paleodrainage relations derived from the Bidahochi Formation, Hopi and Navajo Nations, northeastern
Arizona: The Mountain Geologist, v. 40, no. 3, pp. 55-82.
Ort,
M.H., Orsi, G., Pappalardo,
L., and Fisher, R.V., 2003, Anisotropy of magnetic susceptibility studies of
depositional processes in the Campanian Ignimbrite, Italy; Bulletin of
Volcanology, 65:55-72.
Elson, M.D., Ort,
M.H., Hesse, S. J., Duffield, W.A., 2002, Lava,
corn, and ritual in the northern Southwest; American Antiquity, 67:119-135.
Hooten, J.A., Ort, M.H., 2002, Peperite as a Record
of Early Stage Phreatomagmatic Fragmentation Processes: An Example from the
Hopi Buttes Volcanic Field, Navajo Nation, Arizona, USA, Journal of Volcanology
and Geothermal Research, 114:95-106.
Ort, MH, Elson, MD, and Champion, DE, 2002, A paleomagnetic
dating study of Sunset Crater Volcano; Desert Archaeology, Inc. Technical
Report No. 2002-16, 16 p.
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.
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
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/
Wendell Duffield, retired from the
USGS, serves on many graduate thesis committees and is actively involved in the
volcanology courses. http://oak.ucc.nau.edu/wad3
The SESES home page, where you can
find information on the academic programs, is http://nau.edu/CEFNS/NatSci/SESES/
created by Michael Ort, michael.ort@nau.eduNOSPAM
Dept. of Geology and Center for Environmental Sciences and Education, Northern Arizona University, Flagstaff, AZ 86011 USA
URL: http://jan.ucc.nau.edu/~mho