SEMINAR - Christian Koeberl

Meteorite impact cratering on Earth:
Geological and biological consequences

Dr. Christian Koeberl
Department of Geological Sciences
University of Vienna, Austria

Wednesday, December 5th, 1:00pm GMCS 422

Impact is a unique, short-time, high-energy geological process. The importance of impact cratering on terrestrial planets (Mercury, Venus, Mars), our Moon, and the satellites of the outer planets is obvious from the abundance of craters on their surfaces. On most bodies of the solar system that have a solid surface, impact cratering is the most important surface-modifying process even today. On Earth, active geological processes rapidly obliterate the cratering record. To date only about 170 impact structures have been recognized on the Earth’s surface. They come in various forms, shapes and sizes, from 300 km to less than 100 m in diameter, from Recent to 2 billion years in age. Mineralogical, petrographic, and geochemical criteria are used to identify the impact origin of such structures or related ejecta layers. The two most important criteria are the presence of shock metamorphic effects in mineral and rock inclusions in breccias and melt rocks, as well as the demonstration, by geochemical techniques, that these rocks contain a minor extraterrestrial component. In impact studies there is now a trend towards the use of interdisciplinary and multi-technique approaches to solve open questions. In this lecture we will take a look at impact craters on the Earth (and some other planets), and discuss how they formed and how they can be recognized. An aspect of impact cratering that may be underestimated is the influence of impacts on the geological and biological evolution of our own planet. Even the impact of relatively small asteroids or comets can have disastrous consequences for our civilization. There is a 1 in 10,000 chance that a large asteroid or comet 2 km in diameter (corresponding to a crater of about 25-50 km in diameter) may collide with the Earth during the next century, severely disrupting the ecosphere and annihilating a large percentage of the Earth's population. The biological evolution of our planets is punctuated by mass extinction events, of which the one 65 million years ago, which marks the Cretaceous-Tertiary boundary, is probably the best known one. Abundant impact debris marks this boundary, providing a clear link with a major impact event. The Chicxulub impact structure in Mexico, about 200 km in diameter, which resulted from the impact of an about 10-km-diameter asteroidal body, has been identified as the culprit. Understanding of impact structures, their formation processes, and their consequences should be of interest not only to earth and planetary scientists, but also to society in general.


Christian Koeberl is a professor at the Department of Geological Sciences at the University of Vienna, Austria, whose main research interest is the interdisciplinary study of meteorite impact craters, including shock petrography and the geochemistry of impactites, and also works on meteorites. He was the chairman of the European Science Foundation (ESF) “IMPACT” program (1998-2003), and is a member of the International Continental Scientific Drilling Program (ICDP) Science Advisory Group. He has published over 300 peer-reviewed research papers and has written or edited 12 books.

SEMINAR - Anne Sheehan

Seeing Beneath Mount Everest:
Probing a Breeding Ground of Destructive Earthquakes

IRIS/SSA Distinguished Lectureship
Dr. Anne Sheehan
University of Colorado, Boulder

Wednesday, November 28th, 1:00pm GMCS 422

The Himalaya mountains are the product of the largest continental collision in the world today, and are home to large and deadly earthquakes, such as the Pakistan earthquake of October 8, 2005. To understand how the mountains were created and to help quantify the earthquake hazards of this vulnerable region, Dr. Sheehan led a National Science Foundation funded project that included placement of ground motion recorders (seismometers) throughout eastern Nepal and southern Tibet. The seismic stations were installed in areas that are remote and logistically difficult, with challenges including the mountains, weather, scorpions, cobras, and political unrest and guerrilla warfare in Nepal. Much like a medical CT scan, ground motion recordings from earthquakes provide a detailed image of the Earth beneath the seismic stations. The earthquake recordings collected in Nepal and Tibet produce a first-ever glimpse of the earthquake faults beneath the Himalayan mountains, and can be used to determine details of the earthquake faulting processes.

About Dr. Sheehan
Education
Ph.D., Massachusetts Institute of Technology, 1991B.S., University of Kansas, 1984
Positions Held
Professor, University of Colorado, Boulder 2006-presentAssociate Professor, University of Colorado, Boulder 2001-2006Assistant Professor, University of Colorado, Boulder 1993- 2000Fellow, Cooperative Institute for Research in Environmental Sciences 1993-PresentResearch Assistant Professor, University of Nevada, Reno 1992-1993Postdoctoral Fellow, Lamont-Doherty Geological Observatory, Columbia University, 1991- 1992
Honors and Awards
NSF CAREER Award, 1995

Dr. Anne Sheehan joined the faculty at the University of Colorado at Boulder in 1993 and is currently a Professor of Geological Sciences and Fellow of the Cooperative Institute for Research in the Environmental Sciences. Sheehan's research interests include the study of crust and upper mantle structure of the Earth and its relation to tectonic deformation, particularly beneath mountains and plate boundaries. Much of her work includes the deployment of portable seismometers that record both distant and local earthquakes. She has led recent seismic experiments in the Himalaya, New Zealand, and the Rocky Mountains.

Sheehan is an experienced public speaker and has given talks about her research to many school and community groups. Sheehan was the 2005-2006 Science Advisor to CU Science Explorers. This program offers hands-on workshops throughout the state of Colorado on science topics to teams of middle school teachers and students. Sheehan worked with Science Explorers staff to develop a curriculum on Natural Hazards, including earthquakes and tsunamis, avalanches, and forest fires. Sheehan teaches introductory geology at the University of Colorado to a class of 180 students, and consistently receives high marks for her teaching. She also teaches advanced undergraduate level and graduate level courses in geophysics and seismology.
Sheehan is married and has two school-age children. She enjoys coaching youth sports and participating in triathlons and bicycling events. Sheehan is a breast cancer survivor and is active with Rocky Mountain Team Survivor.

Books
Burger, H. R., A. F. Sheehan, and C. H. Jones, Introduction to Applied Geophysics: Exploring the Shallow Subsurface, W. W. Norton Publishers, 2006.

Selected Recent Publications
Schulte-Pelkum, V., G. Monsalve, A. F. Sheehan, M. Pandey, S. Sapkota, R. Bilham, and F. Wu, Imaging the Indian subcontinent beneath the Himalaya, Nature, v. 435, pp. 1222-1225, 30 June 2005doi:10.1038/nature03678, 2005.De la Torre, T., and A. F. Sheehan, Broadband seismic noise analysis of Himalayan Nepal Tibet Seismic Experiment, Bull. Seismol. Soc. Am., v. 95, 1202-1208, doi:10.1785/0120040098, 2005.Sheehan, A. F., V. Schulte-Pelkum, O. Boyd, and C. Wilson, Passive source seismology of the Rocky Mountain region, in The Rocky Mountain Region: An Evolving Lithosphere, Geophysical Monograph Series 154, 10.1029/154GM23, p. 309-315, 2005.
Boyd, O. S., C. H. Jones, and A. F. Sheehan, Foundering lithosphere imaged beneath the Southern Sierra Nevada, California, Science, v. 305, 660-662, 2004.
Gilbert, H. J., and A. F. Sheehan, Images of crustal variations in the intermountain west, Journal of Geophysical Research, v. 109, B03306, doi:10:1029/2003JB002730, 2004.
Blume, F., and A. F. Sheehan, Quantifying seismic hazard in the Southern Rocky Mountains through GPS measurements of crustal deformation, in Engineering Geology in Colorado: Contributions, Trends, and Case Histories, eds. D. Boyer, P. Santi, and W. Rogers, Association of Engineering Geologists Special Publication No. 15, Colorado Geological Survey Special Publication 55, 2003.Lastowka, L. A., A. F. Sheehan, and J. M. Schneider, Seismic evidence for partial delamination model for Colorado Plateau uplift, Geophys. Res. Lett.,v. 28, 1319-1322, 2001.
Sheehan, A. F., Microearthquake study of the Colorado Front Range: Combining research and teaching in seismology, Seismol. Res. Lett., v. 71, 175-179, 2000.Savage, M. K., and A. F. Sheehan, Seismic anisotropy and mantle flow from the Great Basin to the Great Plains, western United States, Journal of Geophysical Research, v, 105, 13715-13734, 2000.Sheehan, A. F., P. M. Shearer, H. Gilbert, and K. G. Dueker, Seismic migration processing of P-SV converted phases for mantle discontinuity structure beneath the Snake River Plain, western United States, Journal of Geophysical Research, v. 105, p. 19055-19065, 2000.Shen, Y., A. Sheehan, K. Dueker, C. de Groot-Hedlin, and H. Gilbert, Mantle discontinuity structure beneath the southern East Pacific Rise (MELT experiment region) from P-to-S converted phases, Science, v. 280, 1232-1235, 1998.Dueker, K. G., and A. F. Sheehan, Mantle discontinuity structure from mid-point stacks of converted P to S waves across the Yellowstone hotspot track, Journal of Geophysical Research, v. 102, 8313-8327,1997.

2007 Science Sampler

Science Sampler

Sunday, November 18, 2007

A Science Experience on for San Diego Area High School Students Given by SDSU School of Sciences Departments

The Menu:
Oriented toward San Diego County High School Students. A series of short presentations, experiments and labs Hands on, interactive activities demonstrating scientific principles. A sampler of the best of selected science fields. Visitor participation includes a write-up and proof of attendance certificate.

Purpose for High School Students:
Expose High School students to neat science stuff. Experience science in action and take part in experimental science.

Purpose for High School Science Teachers who are welcome:
Support local High School Science Teachers: Provide a local field trip and meet Selected State of California Science Standards

Science Areas:
SDSU School of Sciences Departments Instructions: Students can come by themselves or with others. Suggested arrival at SDSU before 1 :30 PM. for pre-show tour. Go to Geology, Mathematics, Computer Science (GMCS) building Room 333 at SDSU

Campus Directions and Parking Information GMCS Map

November Crossword Puzzle - Seismology

Java Interactive Puzzle

Printable Puzzle (pdf)

SDSU Geology Faculty, Staff, and Alumni Help Support Injured Soldiers Program and San Diego Adaptive Sports Foundation

SDSU Geology Faculty, Staff, and Alumni David Huntley, Marie Grace, Diane Murbach, Monte Murbach, and Matt Weidlin Join the fifth annual Shelter Island 5K RUN/WALK to benefit the Injured Soldiers Program (Injured US Military)and the San Diego Adaptive Sports Foundation.

Dave Huntley came in FIRST in his age group and Diane Murbach came in THIRD in her age group for women.

Registration & Results

SEMINAR - Gareth Funning

Space geodesy in the San Francisco Bay Area: surface deformation, fault kinematics and creep

Gareth Funning
Department of Earth Science
Univeristy of California Riverside

Wednesday, November 14th, 1:00pm GMCS 422

Pacific-North America relative motion is accommodated north of San Francisco on a series of sub-parallel strike-slip faults. From GPS data, we understand the broad distribution of slip between these stuctures, but data are too sparse to map the deformation in detail. However, using an advanced form of InSAR processing - the Permanent Scatterer method - we can generate a dense spatial dataset of surface velocity measurements. There now exist three such datasets for the Bay Area, each from a different viewing geometry/satellite track.

We find a variety of nontectonic and tectonic signals in these data, ranging from ground subsidence and landsliding to strain accumulation and fault creep. I will prsent a series of case studies from around the Bay Area, showing how the different observation geometries can be used to make first order inferences of horizontal and vertical velocities in deforming areas, how the data were used to identify creep on a fault previously considered locked, and how using the pattern of creep on the Hayward fault - currently considered the most dangerous structure in the region - a series of locked asperities can be imaged geodetically.

Inner Space/Outer Space

Department Photo Gallery

SAGE Turns 25

A model of success
Summer of Applied Geophysical Experience program turns 25

It's as heavy as a cement truck, but it works like a watch," said 1 Lawrence "Larry" Braile, a professor from Purdue University. He was referring to the massive, roaring industry-grade piece of machinery called the Vibroseis truck shaking the ground on a mesa near Santo Domingo Pueblo roughly half way between Santa Fe and Albuquerque. Braile, other instructors, and twenty-four students participated in the Laboratory sponsored Summer of Applied Geophysical Experience (SAGE), which turned 25 this summer. The machine is what industry calls a truck-mounted vibrator. The Vibroseis truck, through a heavy pad on the ground, sends benign vibrational waves as deep as two to three kilometers into the ground that refract and reflect off layers of higher density, showing the students and the instructor where there is a change in the rock layers, for example. For the past 25 years SAGE has attracted the best students from around the world interested in geophysics. The application process isn't difficult; however, students must meet certain academic standards, such as successfully completed courses in physics and math. SAGE instructors are mostly looking for interest and motivation. A major in geophysics is not required. Members of the SAGE faculty are among the best in the nation. Additionally, SAGE attracts some the best companies in geophysics, geology, and geological/mineral exploration. Students at SAGE familiarize themselves with state-of-the-art equipment and the latest software, much of it donated by companies. Interest, motivation, and dedication drive SAGE. In the dry desert air with a storm looming to the west, a level of focus and eagerness to learn permeated through students and instructors alike. SAGE is outstanding and long lasting because of its instructors, the core six who have been with SAGE most of the 25 years. The core faculty consists of

• Scott Baldridge of Geophysics (EES-1 I), co-director
• George Jiracek, co-director and professor of geology from San Diego State University
• Lawrence (Larry) Braile, professor and department head of earth and atmospheric sciences, Purdue University
• Shawn Biehler, professor of earth sciences at University of California, Riverside
• Bernard (Bernie) Gilpin, professor of physics and geology at Golden West College
• John Ferguson, associate professor and program head of the geosciences department at the University of Texas.

According to Baldridge, the faculty is "like a good baseball team. They work together well, and there is a high level of individual commitment." Besides the core faculty, several newer staff members from Los Alamos, the U.S. Geological Survey, and Green Engineering consulting firm have joined the program to advance the students' experience. In addition, geophysicists from several companies lead field experiments and assist with instructing students. Since the beginning of the program, a huge focus has been on what could be improved for the next session. How could the students get a more satisfying experience from SAGE?

The faculty has made SAGE a flexible and adaptable program. SAGE,like any long-surviving program, has undergone changes that have been"more evolutionary than revolutionary," said Baldridge.An example of such a change is the size and length of the program.The first SAGE program in 1983 had 42 students and lasted six weeks. Incontrast, the 25 SAGE program had 24 students and lasted three weeks,allowing each student to have hands on experience and individualattention without completely exhausting the instructors.The original SAGE was intended for students of participating facultyonly. Now, student diversity is a main goal and is oft cited as one ofthe most valuable characteristics of the program. Though some of theforeign nationals in SAGE currently are studying in the United States,students from Mexico, Saudi Arabia, Lebanon, Germany, Sweden, andIndia have participated in SAGE.The structure of SAGE also has undergone change to ensure each studentgets the full experience. Instead of having one big group of studentsworking sequentially from project to project, students are split up intoteams and spread out around the area where SAGE is working at the time.In addition to the major support of the Department of Energy and theNational Science Foundation, a significant portion of SAGE is funded byindustry involvement. Companies support SAGE with funding, personneland the latest software and equipment. The Vibroesis truck was donatedto SAGE by the executive vice president of Input/Output, a former SAGEstudent himself.Companies are in turn invited to send representatives to SAGE to talkto, work with, and help teach students. Representatives promote jobopportunities in the field and bring a sense of reality to the work."We're really interested in this experience," said Betsy Torrez, geosciencerecruiting coordinator from ConocoPhillips. "We want to help outand enhance the program here, as well as offer career opportunities."After 25 years, SAGE is running like clockwork. It's had its own "downyears," said Baldridge, but it survived with support from the industriesinvested in SAGE. And like a fine wine, SAGE is only improving thanks tothe faculty's dedication to providing the students' with a quality experience,and the general willingness to be flexible.

by Caryn Johansen
LOS Alamos Newsletter, Week of October 22, 2007

SEMINAR - Jasper Konter

The Origin and Geologic Evolution of Seamounts in the Pacific Ocean

Jasper Konter
Department of Geological Sciences
San Diego State University

Wednesday, November 7th, 1:00pm GMCS 422

The “hotspot” hypothesis predicts that time-progressive linear chains of oceanic intraplate volcanoes (OIV) are formed on tectonic plates that pass over buoyantly rising plumes from fixed deep mantle sources. However, this hypothesis has been called into question by an alternate mechanism, which explains OIV chains by lithospheric extension and mantle melts rising to the surface along lithospheric fractures. Distinguishing between these models is very important because they imply a profoundly different dynamic and chemical state of the mantle that is likely to substantially influence the chemical evolution of the Earth. I will present new geochemical data from a geochemical study of several seamount chains in the Western Pacific, all likely erupted over the seismically anomalous Pacific mantle. These data provide a >100 myr geochemical record that can be related to three geochemically distinct active OIVs in the Cook-Austral region with the help of plate motion models. In a geophysical and geodynamic context these volcanoes should most likely be viewed as the result of deep mantle plumes, while lithospheric cracks are probably a secondary factor.