What is this?!!1?1!? |
There I was, fiddling around looking at rock types and contacts. The map wasn't easy to look at in Google Earth (GE) because it was in black and white, so I started drawing the contacts on to GE, and lo and behold, the contacts were all screwy. It took me a while to figure out that the kmz file didn't register properly on GE; perhaps it didn't have a NAD27 to WGS84 correction or some such thing. I plotted a few static, known localities that I could identify on both the map and GE and determined that everything was off in a northwesterly direction (map to GE) by about 1500 to 1900 feet.
The map and GE locations of a small dam and the ghost town of Palisade. |
I was frustrated by this mis-registration of the map on Google Earth—what is the point of a kmz file of a map, after all, other than to be able to use it easily and forthwith—so I continued drawing on a few contacts in the area I was initially interested in: the area near the small (or old) dam shown above.
Oh look, there's a huge landslide or slump block mapped! I always find these fascinating, so I zoomed in on that, after figuring out that, indeed, I had stopped along the road once—in a pullout near the dam—and had found ash-flow tuff in the roadcut, just like I had remembered! (Although in this case, it was probably slumped or slid ash-flow tuff rather than 100%-in-place ash-flow tuff.)
And then I remembered that I'd always thought there was a pediment in Pine Valley, and recent drives through the area seemed to confirm that, though I wasn't sure if it would be considered a pediment because it seemed to be formed on Quaternary-Tertiary sediments. A couple of old reports (Regnier, 1960 and Eakin, 1961) confirmed that a pediment (or two, even!) had been identified in the valley—and that's when I went nuts with my GE squiggles, and started drawing in all the Quaternary gravels so I could better visualize the valley's geomorphology. That resulted in the squiggles seen in the first image: an incompletely labeled map with missing contacts but with pediment gravels outlined in great detail.
Then, I moved up to Carlin Canyon and—unsuccessfully in my opinion—tried to plot the unconformity contact. (See Ron Schott's Gigapan of the Carlin Canyon unconformity here.) And then I moved to the Carlin Formation east of the Carlin Tunnels. The Carlin Formation forms golden-brown outcrops and cliffs right alongside the highway, great examples of tafoni weathering, so close but inaccessible. I wanted to see if any roads led into the area, and there are none, but I drew some squiggles for the geology in that area anyway, and then moved south of the highway to draw in a few more areas of the Carlin Formation, because once I've started on something, it's hard to get me to stop.
An expanded version of my GE squiggles. |
By the way, the completed geologic map (Smith and Ketner, 1978), published in color, can be viewed here (but without a kmz file).
2 comments:
looks like that KMZ was done at 1:25,000 ... not sure what scale you were viewing, but it is not much good any closer. :)
The kmz's usually adjust to whatever scale they are viewed in on Google Earth, so I don't think that should matter any. That is, all the USGS kmz files I've used before have been just fine at any zoom on Google Earth. (Although I might not always agree with all the contacts, they have always overlaid the topography exactly before this.)
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