August 7, 2012
Charles Darwin, writing on the HMS Beagle, January 11, 1832:
“Again did I admire the rapid course of the setting sun. — It did not at first occur to me that it was owing to the change of Latitude”
I was reading through my old notes from a class about Darwin and noticed the snippet above. Moments ago I glanced out the window and thought, “Damn but it is so dark out!” It’s 6:40 pm California time. What Darwin experienced during five years at sea we can now experience in hours. I’m flying into the night. Soon I’ll be flying into the winter. I am a Greek myth right now.
10:02 California time. Soon we’ll be descending into Lima. Baggage check, a taxi to the hotel.
I’m crossing my fingers I get enough sleep to act sensibly tomorrow. Tomorrow is a big day. In the afternoon we’ll go to the university and meet the chair of the geology department. She wrote her dissertation on these rocks, specifically, how they formed 200 million years ago in the crucible of plate tectonic motion.
While I’m in Lima, my favorite seismologist is flying to Alaska. What, do we think California’s mighty San Andreas fault is too boring?
[If you’re reading this and live in southern California, stop by the market later today for a couple gallons of water to store in your home. The southern San Andreas is overdue for what Angelenos cheerfully call, “the big one”.]
The San Andreas cuts right through California. People joke that California will “fall off” of North America but actually it’s just the opposite. California is built out of geological what-nots that SLAMMED onto the side of North America. Conveniently for us, the famous San Andreas represents the seam between the true North American plate and the enormous Pacific plate. Right now, around North America, the two are basically sliding past each other. So whatever earthquakes the San Andreas and friends dish out will be at least a mutual affair. In the grand scheme, both plates get what they want.
Consider two plates colliding head-on. Look at Peru via Google Satelite. Google now includes details of the seafloor topography; now we can look right at the seams the separate these tectonic plates that are hidden under water. It took geologists decades to find and interpret this information, and now any ten year old can google it on an iphone. Mind boggling!
Via Google we can see a chunk of crust under the ocean named the Nazca plate. This one is diving under Peru right now. Only, I wouldn’t call it a mutual affair between the plates. No, this one is very unpleasant. At their collision, an enormous belt of mountains forms – those mountains are my destination on Friday.
When Charles Darwin sailed around South America on the HMS Beagle, he was as much a geologist as biologist. But he, like the rest of his society, was totally baffled at the puzzles hidden in rocks and fossils. The very concept that a mountain of sedimentary rocks might have formed slowly over time was still a new topic of discussion. How MUCH time was hotly debated and politically perilous.
Enter Darwin, young, rich, curious, and very sea sick. He spent much of his journey exploring the land while the ship surveyed the coast. [His entire diary from the five year trip is online, and is a fascinating read. Insofar as I have time I’ll find and share snippets.] Darwin marveled at sea shells high up on coastal cliffs. Did the sea level fall or did the cliffs rise up?
Before long Darwin got an answer first hand. He was in the forest in Chile when a huge earthquake shook the land, literally knocking him on his butt. Later the Beagle traveled north to Conception, which was wrecked terribly in the quake. Because of his earlier observations, Darwin recognized rocks moving up, containing the fossils of sea shells from an earlier time. This process built the mountains that contain sea shells from the Mesozoic, fossils I hope to recognize later this week in the field.
It’s pretty convenient for me. Animals lived and died on the seafloor 200 million years ago, and I get to wait for them to be moved about and exposed in beautiful mountains, where I just show up and look at them. Time travel, made easy.
Ah, ready for descent. Time to pack up, and turn off the computer. Next time I write will likely be after my first day at the university.