Wednesday, August 28, 2013

The F I E L D pt. 3

The O U T C R O P S

The days have come!!!$Q#^ Finally, we've made it to the fabled outcrops. And yes, they do exist! After spending our first full day driving the nearly 10 hours from Vancouver to our first stop in Horsefly, British Columbia, the whole crew was well rested. Our stay in the Horsefly Lake Provincial Park was welcomed, but we were ready to head out to start sciencing. 
The distance from Vancouver, at the bottom middle, to Horsefly is equivalent to driving from Los Angeles to San Francisco. And we hardly put a dent in British Columbia.

Since we were denied access to our first site via the private property, we chose to move on to our aptly named second site, Horsefly 2. 

That time we lost Hari, who at first went to relieve himself, but then we decided to meet him 5km down the road while drove and he hiked.


On our first day out, we opted to take all 6 of us by RV. This seemed like the most sensible decision, as not all would fit in our secondary vehicle, and the RV carried all our food, snacks, and beverages (#duh). What we did NOT anticipate were that the ridges in the dirt road we drove for 30+km at 50km/hr vibrated the RV somewhere near resonant frequency. 
A TANGET: ~Resonant Frequency~ 
 n. The frequency at which an object oscillates with highest amplitude. 

  •     In the case of mechanical resonance, the object vibrates at a maximum of frequency amplitude.
  • When this uncontrollable vibrations occur, they may cause serious damage to structures (think, our shoddy Cruise 'Merica RV), in what's called resonant disaster. 

Artistic interpretation of mechanistic failure in Tacoma Narrows Bridge during vibration event.
.... And here are some of the things we found in Horsefly!
J Caves

The hike to find Hari and the river-cut outcrop.

Matt harnesses the power of wolves to collect samples.
The outcrop of interest was along the river that fills Horsefly Lake. It featured Eocene lacustrine sandstones with interstitial carbonates (we're talking about FLAM: Fizzin' Like a Mother F*****!!) that record the meteoric water at the time of their deposition some 54 million years ago. The outcrop was exposed in modern times by the running and incision of the river, whose own waters have most likely altered the carbonates at the surface. Our method involves: identifying the familiar stratigraphy we studied in earlier papers, locating laminae of interest, banging away the rock for a fresh surface, then fizzing away (if possible) with small drops of dilute HCL (1m) that Hari helped me prepare earlier in the summer. 
It requires a keen eye and familiarity with the history of the site to identify useful layers in the rock record before you. A good geologist has to be perpetually skeptical of the history recorded in his samples, since in the last 50 million years, much could have happened to alter that recorded in the minerals before him. At one point, I had my first semi-confident find of the day in a FLAM sample. I pointed out the dark red-brown layer in the photo above, something of thin crust separating it from the layers above and below it. Dan identified it as a caliche, a thin crusty layer of carbonaceous cement, possibly the result of Eocene deposition, or possibly a product of modern groundwater leaking through weaker layers of the rock. Hopefully the first! Only time will tell, after processing reveals if it fits, as expected, into our data set. 

All in all, it was a productive first site. 




Images Courtesy

http://www.wsdot.wa.gov/tnbhistory/machine/machine3.htm

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