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DR. GARY SMITH |
Composite volcanoes are among the most impressive and yet least well understood of volcanic landforms. Many variables determine the evolution and internal structure of a composite volcano. We are endeavoring to better understand the processes responsible for forming these cones. Our emphasis is on fragmental deposits and work, to date, shows that volcanic breccias comprise more of many composite volcanoes than is typically represented in the literature. We also find that most of these breccias are composed of autoclastic, rather than pyroclastic, materials necessitating revisiting of popular composite-volcano diagrams featuring alternation of lava flows and tephra. Pyroclastic deposits have limited preservation potential on steep cone slopes. Autoclastic breccias have also been inaccurately interpreted as "lahar" deposits in many cases. A better understanding of how composite volcanoes grow and the origin of fragmental deposits comprising them is also important for evaluating the stratigraphy of volcaniclastic-sediment aprons that form adjacent to the volcanoes. Our study sites are highly dissected Tertiary and Quaternary volcanoes of the western United States and New Zealand.
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Publications:
What factors control the composition of andesitic sand?
G.A. Smith and J.E. Lotosky
Journal of Sedimentary Research, v. A65, p. 91-98, 1995.
Volcaniclastic rocks of the Keres Group: insights into mid-Miocene volcanism and sedimentation in the southeastern Jemez Mountains
A. Lavine, G.A. Smith, and F. Goff
New Mexico Geological Society Guidebook, 47th Field Conference, The Jemez Mountains Region, F. Goff, B.S. Kues, M.A. Rogers, L.D. McFadden, editors, p. 211-218, 1996.
Volcanic breccias: Evaluation of fragment and deposit origins and distribution within small-volume composite volcanoes
Michael Grubensky
University of New Mexico, Ph.D. dissertation, 1996.
Sedimentologic and temporal relations between volcanic and volcaniclastic rocks of the Keres Group, Jemez Mountains: Implications for the physical and volcanic evolution of Keres Group composite volcanoes
Alexis Lavine
University of New Mexico, M.S. thesis, 1996.
Field classification and paleomagnetic characterization of lithic and scoriaceous breccias, Pleistocene Broken Top volcano, High Cascade Range, Oregon
M.J. Grubensky, G.A. Smith, and J.W. Geissman
Journal of Volcanology and Geothermal Research, v. 83, p. 93-114, 1998.
Nature and origin of cone-forming volcanic breccias, Te Herenga Formation, Ruapehu Volcano, New Zealand
G.A. Smith, J.W. Geissman, M.J. Grubensky
submitted to Bulletin of Volcanology, v. 69. P. 675-689, 1999.
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