Presents
Location: Stanford University
This will be the 453rd meeting since 1954
(Image from Hernan Canellas)
It has been known since the Apollo era that the lunar rocks and crust are magnetized. Until recently, it was unclear whether the magnetizing fields were generated by a dynamo or by processes external to the Moon. New paleomagnetic and spacecraft measurements strongly indicate that much of this magnetization is the product of an ancient core dynamo. Between at least 4.25 and 3.56 billion years ago (Ga), the dynamo produced surface fields with intensities similar to that of the present Earth. The field then declined by at least an order of magnitude by ~3.3 Ga, but may have persisted in a weakened state beyond this time. When the dynamo ultimately ceased remains unknown. The mechanisms for sustaining such an intense and long-lived dynamo are uncertain but may include mechanical stirring of the core by the mantle and thermochemical convection from core crystallization.
Sonia Tikoo
Sonia Tikoo uses paleomagnetism as a tool to investigate problems in planetary science such as core formation, dynamo generation, and impact cratering. Sonia earned her B.S. in Geology at the Caltech in 2008, and her Ph.D. in Planetary Science from MIT in 2014. She is currently a Postdoctoral Researcher at the University of California, Berkeley, and the Berkeley Geochronology Center.
Reservations: The preferred way to make reservations is simply to email Mike Diggles at mike@diggles.com by Apr. 12, tell him you will attend, commit to pay, and bring your payment to the meeting. Mike always emails a confirmation; if you don’t get one, assume email crashed yet again and email him a second time. A check made to “PGS” is preferred, payable at the meeting.
If you want to pay in advance:
Everyone (including Stanford folks now) Please make dinner reservations by Apr. 12. Contact Mike Diggles, at U.S. Geological Survey, 345 Middlefield Road, MS-910 Menlo Park, CA 94025, Tel.: (650) 329-5404. Send check made out to “PGS” to Mike.
Dinner and the social hour is $35.00; this includes $5 that we use to help pay for students who are only $8.00 (also partially subsidized thanks to the School of Earth Sciences, Stanford University (Note, no-show reservations owe the full price).
Doris, whose wonderful crew prepares our meals, asked that we let you know that people who are late RSVPing and people who show up without a reservation will be welcome but that they may be eating on paper plates with plastic utensils (food supply permitting).
Dues for Academic Year 2014-2015 ($10.00) should be sent to Mike Diggles, U.S. Geological Survey, 345 Middlefield Road, MS-910, Menlo Park, CA 94025. Mike’s phone: (650) 329-5404.
Officers: Brad Buerer, President; Sarah Nagorsen, Vice President; Mike Diggles, Secretary-Treasurer; Elizabeth Miller, PGS Stanford University Coordinator
PGS cartoon by Rick Blakely
Date created: March 29, 2015
Last modified: June 6, 2015
Created by: Mike Diggles, Webmaster-Secretary-Treasurer, PGS.