The majesty of the icefields is beyond description. He who has been fortunate to be there once, remains bound forever. To a theoretical physicist working on black holes the icefields produce a familiar vertigo, the instinctive certainty of being confronted with something so simple and beautifully extreme that it must be of importance. The meeting whose proceedings are contained in this volume was conducted onboard of a vessel that went to the icefields, and the participants could literally set foot on them. It was expected that, for those who had not been there before, this would constitute a ritual of initiation. And so it did. For this reason we like to refer to the meeting as an expedition because, although it did not have the hardship, it had the spirit. After this foundational expedition there have been two others, this time both with spirit and hardship, one from Chile and one from Argentina. At the moment of this writing, a fourth, full-fledged airborne expedition to the icefields is about to depart from Valdivia. Many of the people of many nations who were on board of the Aquiles will take part in it. We look forward to its results, and to an ongoing exciting scientific adventure. Claudio Teitelboim Director, Centro de Estudios Cientfficos Valdivia, September 2001 v ACKNOWLEDGMENTS This volume is the result of the effort and generosity of many people and institutions.