On top of all the other big historical moments that have had their 50th anniversaries this year–the moon landing, Stonewall, Woodstock–I was delighted to discover, in John McPhee’s book Assembling California, another one I’d never known about. 1969 was the year that the theory of plate tectonics, which had been fighting for years to gain acceptance among old-guard geologists, finally came into its own as the prevailing understanding of how our planetary surface has formed.

“In Pacific Grove, California, at the end of 1969, a Penrose conference on ‘The Meaning of the New Global Tectonics’ drew structural geologists from all over the world. William Dickinson, of Stanford, dismantled the geosyncline and assigned its parts to various aspects of plate tectonics–collisions, island arcs, abyssal plains, melanges, trenches, transform faults. Moores describes the conference as ‘a watershed of geology–that was when people really began to realize how important plate tectonics was.'”

A quieter moment than Woodstock, obviously, but I love thinking that the big year 1969 also marked a new era in the human vision of earth.

The conference occurred in early December, if you care to raise a glass.