30 March 2013

Benchmarking Time: Washington, DC

Posted by Jessica Ball

There’s been a long delay between posts because I was working flat-out for a few weeks to get ready for my last committee meeting – which is done! Now I have a date for my technical defense in May, and I decided to take a few days off to visit my family for Easter. (I’m avoiding grad student guilt by reminding myself that I worked all through what should have been my spring break and that if I didn’t take a few days off I was going to crack.)

I spent yesterday in downtown Washington DC, hoping to see a few blossoms on the Yoshino cherry trees around the Tidal Basin (it’s a big thing here), but unfortunately it’s been a bit too cold for them lately, and the peak bloom won’t be for another few days. There are a few trees out, just not in the popular areas around the Tidal Basin.

Not much in the way of blossoms yesterday...

Well, okay, there was ONE blossom.

What I did find were a couple of benchmarks! The first is on the Tidal Basin itself (there were several near the walkway), and it’s a Park Service marker. There’s no elevation on it, so I guess it was only used for surveying in the horizontal plane? (Putting a permanent benchmark with a set elevation next to the Tidal Basin would actually be a tricky prospect, since the ground out there is known to subside and there have been restoration projects aimed at fixing this.)

Tidal Basin marker near the intersection of Maine Avenue and 14th Street

On my walk around the Tidal Basin, I stopped at the new Martin Luther King Jr. Memorial, which is (if you’re walking clockwise around the water) just after the Jefferson and Roosevelt Memorials. It’s very striking from a distance, and pretty impressive close-up.

The new MLK Memorial on the Tidal Basin

The main quote that’s embodied by the memorial itself is “With this faith we will be able to hew out of the mountain of despair a stone of hope.” It’s a neat visual metaphor, although as a geologist I was also interested in the stone the mountain’s made out of. It turns out to be very light granite (I would call it a leucogranite), which according to the NPS website was imported from China. I can’t find much about the rock itself (it’s not really addressed in the many debates around the statue, beyond the decision to import the granite rather than use rock from the U.S.).

The leucogranite 'mountain' at the MLK Memorial

Getting away from the monuments for me usually means a stroll through one or more of the Smithsonian museums. My favorite, the Natural History Museum, was too swamped to go into (probably because all the tourists who had no cherry blossoms to see with their kids went for dinosaurs instead), but I was reminded that there’s a benchmark tucked away on the front steps of the museum.

Office of Public Buildings and Parks Benchmark, NMNH

This is a neat one. There was, from 1925-1933, an Office of Public Buildings and Public Parks in the Capital, whose director was responsible directly to the President. The office served much the same purpose as the Park Service (which is in charge of the National Mall) does today, and it was absorbed by the Department of the Interior’s Office of National Parks, Buildings and Reservations in 1933. The NMNH opened in 1910, so it looks like this benchmark was put in place at least 15 years after the museum was built. If you look closely, you can see that the marker isn’t quite dead-center in the hole that was drilled for it, which suggests to me either slightly sloppy workmanship or, if the marker was drilled all the way through the step (it’s at the bottom of the staircase) and properly embedded in concrete like other geodetic markers, that the steps themselves may have shifted. Either way, it’s a historically interesting find. It’s located just below the petrified logs on the east side of the National Mall entrance.