Compres

In 2008-2009, COMPRES inaugurated a new distinguished lecture series in the field of mineral physics. This new initiative was developed by J. Michael Brown, a member of the Executive Committee who organized the program and led the selection of the lecturers for the first year of this program [Wendy Mao of Stanford University and David Walker of Columbia University]. For 2009-2010, Carl Agee led the selection of the distinguished lecturers. The goals, purpose and charge to lecturers are given below.

Purpose:  As an important outreach activity for COMPRES, the series will promote a better understanding of the outstanding science and the nature of geoscience research in the early 21st century. Two clear audiences are recognized. (1) our colleagues in related geosciences who might not fully appreciate how high-pressure research is contributing to the understanding of Earth processes and who are not aware of the growing need for large scale research facilities, (2) undergraduates who could be recruited into the COMPRES research community.

Charge to speakers:  (1) First and foremost, talk about exciting science using language understandable by a broad audience. (2) Include information about COMPRES facilities and how shared resources like synchrotron beam-lines are expanding opportunities for geoscientists. (3) Be forward-looking and examine the upcoming challenges and opportunities.

COMPRES Distinguished Lecturers for 2009-2010

Jackie Li: Received her B.S. in geochemistry at the University of Science and Technology of China in 1992, M.A. in geophysics at Harvard in 1997, and Ph.D. in Earth and Planetary Sciences at Harvard in 1998. She was a Gilbert Postdoctoral Fellow at the Carnegie Institution of Washington between 1998 and 2000 and continued as a researcher for three more years. She joined the Department of Geology at the University of Illinois at Urbana Champaign as an assistant professor in 2003 and became an associate professor in 2009. Her research interests focus on understanding the nature and evolution of Earth and planetary interiors through experimental investigations of material properties under high pressure and high temperature.

Surface phenomena such as earthquakes, volcanoes and auroras provide fascinating but only basic glimpses of the turbulent processes occurring deep inside planet Earth. Developing a complete understanding of our planet’s inner workings requires specialized and accurate knowledge of material properties under extreme conditions. In the past two decades, synchrotron X-rays and high-pressure instrumentations have opened a new window to the inner Earth.
This talk will showcase how synchrotron X-rays, diamond-anvil cells, and multi-anvil apparatus have helped us 1) decipher the mystery of light elements in the Earth’s core through measuring the density and seismic velocities of iron-rich alloys under high pressures and high temperatures; 2) investigate the composition and properties of the Earth’s lower mantle through probing the electronic spin state of iron in perovskite and post-perovskite.

As a planetary body ages, its internal heat gradually escapes to the surface. In Earth-like bodies, this slow cooling may lead to solidification of iron-rich cores and provide energy sources for magnetic dynamos. In giant planet’s icy moons, this slow cooling may result in freezing of their sub-surface oceans and alter their structure and dynamics.
In this talk, I will show recent experimental results of 1) the iron-sulfur binary system melting at high pressure, which suggest Mercury’s core may actually be “snowing” and which reveal new mechanisms for the planet’s dynamo; 2) the thermal conductivity of water-ices under high pressure, with implications for the thermal evolution history of giant planets’ icy moons.
COMPRES Distinguished Lecturers for 2009-2010

 COMPRES Distinguished Lecturers for 2009-2010

Harry Green
University of California Riverside
Who will offer lectures on

Harry Green: PhD 1968. Educated at Columbia and UCLA. Postdoc in Materials Science, Case Western Reserve University. Faculty member at the University of California for 39 years; 1970-1993 at Davis and 1993-present at Riverside. Currently Professor of Geology and Geophysics and Director of the Institute of Geophysics and Planetary Physics. Research Interests: Flow and fracture of rocks at high pressure and temperature and the effect of stress on phase transformations -- with particular application to subduction zone processes.

Title 1: How do earthquakes occur deep inside the Earth?

Earthquakes near the surface are caused by frictional sliding on pre-existing faults or, rarely, by creation of a new fault by brittle shear failure. Neither mechanism can function at depths greater than ~30-50 km because pressure strongly inhibits frictional sliding and temperature enhances flow. Experiments show that deeper earthquakes, those in subduction zones, require a mineral reaction that generates a small amount of a new phase with very low viscosity -- a "fluid" -- which could be a real fluid (e.g. H2O or melt) or a pseudofluid consisting or a polycrystalline material of nanometric grain size. Work in my lab over the last 20 years has delineated that fluid-producing reactions like dehydration of serpentine are the likely mechanism for earthquake nucleation above ~400 km and that transformation-induced faulting of metastable olivine is the likely mechanism below 400 km. This talk will explore these mechanisms and show how they explain the bimodal distribution of earthquakes with depth, why they stop abruptly before 700 km, that metastable olivine is present in at least 4 subduction zones, and that subducting slabs must be dry below 400 km.

Over the last 40+ years, rocks have been discovered from progressively greater depths in continental collision zones. In particular, in the late 80's coesite was discovered in Italy and Norway and diamonds in sediments from Kazakhstan, giving rise to the field of Ultra-High Pressure Metamorphism, and implying subduction to more than 120 km and return to the surface. More recently, the use of microstructures has extended the evidence in these terranes to much greater depths, culminating in showing that surficial materials have been subducted to at least 350 km (stabilizing stishovite in metapelites, for example) and returned to the surface. Most certainly greater subduction has also occurred and most likely is responsible for the "continental" signal in ocean island basalts. Some peridotites carry "memory" of still greater depths. This talk will explore the evidence for such very deep subduction, the controversies that have swirled around each new discovery, and what these rocks have told us about the upper few hundred km of our planet. I also will touch briefly on a new discovery of very high-pressure minerals in ophiolites that may open a new window into Earth's deep interior in the upwelling limb of mantle convection.