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Thursday, July 29, 2010

The Ultimate in Historic Preservation

I wonder if William Morris, the founder of the modern historic preservation movement, would have enjoyed a visit to the famous Gubbio Section in Italy.  I know you are probably wondering, what the heck is that?  It is an outcrop of rock (see pic below) that preserves a record of deep time, a sequence that somehow escaped being eroded, subducted, buried, washed away, blasted to smithereens, etc.  Here in a deep gorge in the mountains near the medieval town of Gubbio, one finds the beautifully preserved boundary between the Cretaceous Period, the time of the dinosaurs, and the Tertiary Period, the time of mammals rise to dominance (we rule!).

 It is at this famous outcrop that Walter Alverez, Jan Smit, and their colleagues found the telltale evidence for the asteroid impact that slammed into the Earth 65 million years ago bringing with it years of darkness, firestorms, a collapse of the food chain, and the demise of the dinosaurs that had roamed the Earth as the largest vertebrates for over 160 (!) million years.  I first learned of the asteroid extinction hypothesis as an undergraduate, the year it was proposed --- it was considered a profoundly outlandish idea at the time.  Probably the only reason anyone paid any attention at all to it was that it was authored by a Nobel Prize winning physicist, Luis Alvarez, geologist Walter's father.  Thirty years later the hypothesis is widely, although not universally, accepted within the scientific community (as a comparison, I would say there is more scientific consensus on the reality of anthropogenic global warming).

The reason the boundary layer looks like a slanted hole (the rock layers are tilted) is that for decades geologists and others have been digging further and further into the cliff to get samples of the extinction layer.  The guy in the lime shirt is Jan Smit, one of the original proposers of the asteroid impact hypothesis.

 Even though it is the most famous outcrop in the world, this is still really only a place to set a geologist's or naturalist's heart aflutter.  But anyone would appreciate Ristorante Bottaccione, located a few hundred meters down the road.  Here we (about 70 of us!) had a fabulous multi-course lunch on a shaded outdoor patio with many bottles of wine.  We pored over the two Gubbio guest books that have been kept by the restaurant since the first one was started by Walter Alverez in 1976 (he and his colleagues published the hypothesis in 1980 after discovering extraterrestrial iridium in the boundary layer).  A record of the many geologists and Earth Science groups that have visited the outcrop over the years, these books are filled with names of scientists, famous and otherwise, along with their doodles, reflections, comments, etc.  A few years back a museum in France scanned them in their entirety as an epistemological record of the evolution of the asteroid impact hypothesis.  Like my visit to Red House, it was a great feeling to finally visit this amazing place.

The first page of the first logbook...Walter Alvarez at top of list.