Research Interests

My research is geared toward addressing the basic problem of why the Earth behaves as it does. This first requires an understanding of how the Earth is behaving now, and how it is likely to have behaved in the past. Does, for example, the oceanic lithosphere behave as rigid blocks even down to the scale of tens of kilometers, as we assume in plate tectonics? Are the present plate geometries sufficient to explain the transport requirements established for terranes comprising the western North American coast? Does fractured media attenuate acoustic waves in a manner linearly proportional to their permeability? Can the state of stress of a buried formation be predicted in situ? Has the oldest oceanic lithosphere been affected by numerous hotspot crossings over the past 170 m.y. or has there been one or more widespread anomalous volcanic events in Cretaceous time? Can olivine anisotropy orientations, as predicted from past plate motions help explain the velocity contrasts observed in subduction zones? These are some of the questions I have been lucky enough to have had the opportunity of addressing.

BEHAVIOR OF OCEANIC LITHOSPHERE

Propagating Rifts

With Seth Stein, I numerically modeled propagation histories of the Cobb Offset along the Juan de Fuca ridge. This is a special class of propagating rift called a "dueling propagator", where each limb alternately advances and retreats in opposition to the other limb. In order to discriminate between competing models we developed a method which compared computer predictions for each model with the structural fabric data of the seafloor as well as with magnetic anomaly data. We found that the lithosphere was not only behaving in a rigid manner, but also rift propagation occurred at a rate that was much faster than that which is seen by using structures which average rates over several millions of years.

Hotter, Thinner Lithosphere

With Carol Stein (at the University of Illinois, Chicago) and Seth Stein, I have constructed an age map of the Indian Ocean lithosphere and used this along with sediment isopach and bathymetry data to determine age-depth relations for this basin. We found that these data were best fit by a model that is slightly hotter and significantly thinner than the widely used Parson-Sclater plate model.

BEHAVIOR OF CONTINENTAL CRUST

Borehole Geophysics

With Ken Tubman at ARCO Research and Development Company I used borehole geophysical logs to estimate formation elastic moduli and use these to predict in situ stress patterns. With John Castagna (then at ARCO, now at the University of Oklahoma) I have considered whether attenuation of Stonely-waves set up in the borehole by acoustic sondes is related to the permeability of the formation.

PALEOMAGNETISM

Terrane Accretion

With Richard Gordon (now at Rice University) I have re-evaluated and quantified the uncertainties associated with the terrane trajectory of the Laytonville Limestone in California. This unit was formed 14 degrees south of the paleoequator about 100 Ma. It is currently about 40 degrees north of the equator as part of the Franciscan Melange in northern California. The rapid motion required for this track has led to the proposition of a new, now defunct plate (dubbed "Escondido"). We developed a method for estimating the uncertainties in the trajectory and showed that within the uncertainties it was possible to explain the terrain trajectory without any additional plates.

Seamount Paleomagnetism

With Phil Bryan, Katerina Petronotis, Richard Gordon, and Doug Bergersen (then at the University of Hawaii), I modeled magnetic anomaly data collected over the Marshall Islands in the western central Pacific during a cruise of the Moana Wave research vessel in 1988. The Marshall Islands' guyots and seamounts sit on some of the world's oldest seafloor. Our results indicate that all these edifices could not have formed during the passage of a single hotspot or by a single episode of anomalous volcanism during the Cretaceous as had been previously proposed.

SUBDUCTION ZONE ANISOTROPY

With Craig Bina, I have addressed the question as to whether olivine anisotropy directions as predicted by plate motions can help to explain seismic velocity contrasts observed across the slab-mantle interface of the upper 400 km in subduction zones. We found that the effect will vary considerably from region to region and that contrary to expectations, in many cases it actually drives the velocity contrast opposite to what is observed making the subducting slab appear seismically slower than the surrounding mantle for a vertically propagating wave.

FUTURE DIRECTIONS

I intend to continue in the future to attempt to understand important aspects of the Earth's behavior which are reasonably well explained in the broad sense by the paradigm of plate tectonics, but less well understood in detail. Some of the more important questions I hope to have the opportunity to address are whether hot spots move with respect to each other. To do this will require a refinement of the plate - hotspot motion reconstructions as well as quantifying the uncertainties associated with each. What effects do phase changes in oceanic lithosphere have on such surface observables as bathymetry, guyot formation, heat flow and flexure strength? Whether existing paleomagnetic and geochronologic data are accurate enough to consider the details of changes in tectonic regimes which seem to have occurred between the Archean and Proterozoic times. I also wish to establish a firmer understanding of the uncertainties associated with seamount paleomagnetic poles which may serve as our best source of apparent polar wander data through the Cenozoic for oceanic plates like the Pacific or Nazca plates but also for such continental plates as South America, Antarctica, and India, where the rock record for these times are incomplete or inaccessible. Many of these topics of research are suited for short year-long endeavours that could reasonably be accomplished by an motivated undergraduate student as well as graduate students.

Science Education

Educational Outreach

I also have a great concern for the state of education in the lower schools of our nation as well. At Pittsburg State University I have had the opportunity to work with teachers in the SE Kansas and SW Missouri area. I have, together with Todd Van Gorden at PSU, put together workshops for middle and secondary school teachers on Solar System Astronomy, Earth Science and Environmental Science. Also as part of my duties as the science education coordinator of the Physics department I have the responsibility of helping to set the curriculum at Pittsburg State University which satisfies the state requirements for certification in the areas of Physics, Earth Science and Physical Science.