Saturday, February 12, 2011
Accretionary Wedge Carnival #31: Geological Surprises and the Abyss of Time
Jazinator is hosting the 31st Accretionary Wedge, asking:
What geological concept or idea did you hear about that you had no notion of before (and likely surprised you in some way)?
Part of my wedge entry comes from an earlier blog post (self-plagiarism?), but I was actually talking about something else at the time, the discovery of my first fossil.
From Geotripper in May of 2009:
"It took only a split second to take me back forty years to the North Rim of the Grand Canyon, where a 10 year old boy was on his first trip to the beautiful national park. But I had found out something strange at the small visitor center there. The ground I was walking on at more than 8,000 feet had once been on the bottom of the sea! Say what? How could that be? I was already at an age where I had figured out that Noah's Flood couldn't account for this. Where was all the water that it could even cover Mt. Everest and all the other mountains of the world? It was clear that something had happened, but I wasn't quite in a place where I could understand the idea of vast uplift across an entire region. I spent days musing about this, enough that the memory is clear after all these years."
It was years before I revisited the problem of marine rocks at the tops of mountains and high plateaus (I had all those teen years to get through), but it made a huge impression on me that the Earth's crust was so mobile that it could lift mountains and plateaus out of the sea. It was one of the life-long mysteries (hey, 10 years to a 20-year-old is half a lifetime!) that plunged me into a career as a geologist and teacher. It might seem almost a mundane observation once a geologist has explored the depths of the crust and mantle and the full breadth of geological history, but a first realization is a powerful thing.
A human life is a series of discoveries that replay the discoveries of mankind in compressed time. Those who came before us paved the road for our understanding, allowing us to comprehend in a few days or months what took others decades or centuries to discover (I teach the basics of plate tectonics in 40 minutes or so, when it took the greatest geological minds 50 years to discover and accept the concept). When I read of James Hutton and John Playfair discussing the geology at Siccar Point (below) in Scotland in the late 1700's, I realized that a similar revelation was the foundation of an entire new science:
"What clearer evidence could we have had of the different formation of these rocks, and of the long interval which separated their formation, had we actually seen them emerging from the bosom the deep? We felt ourselves necessarily carried back to the time when the schistus on which we stood was yet at the bottom of the sea, and when the sandstone before us was only beginning to be deposited in the shape of sand or mud, from the waters of a superincumbent ocean. An epocha still more remote presented itself, when even the most ancient of these rocks instead of standing upright in vertical beds, lay in horizontal planes at the bottom of the sea, and was not yet disturbed by that immeasurable force which has burst asunder the solid pavement of the globe. Revolutions still more remote appeared in the distance of this extraordinary perspective. The mind seemed to grow giddy by looking so far into the abyss of time...."
To those students, geologists, teachers and bloggers who haven't contributed to the Accretionary Wedge before, think about it! I know I have a few students who blog on geological topics. If you don't blog, but would like to contribute, I would be more than pleased to host your entry as a guest-blogger on Geotripper. Jump in!