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Ok. I moved the blog. This is my inaugural post.

Lately I have been desperately trying to finish up some maps that are really going to get in the way as a huge project looms larger and larger…and I mean larger. Today I spent some time working on the Spirit Mountain Northwest Quad.  This is one of those maps that has some intricately stacked  stuff in a few relatively small areas that are separated by large swaths of planimetrically intricate but geologically straightforward surficial deposits. Also, this map has a big fat lake in it…freebie! Right?

Well, no. Turns out that I am interested enough in the history of the Colorado River to have claimed that I will do what I can with what is available to map the submerged geology. Luckily, the USGS recently published a bunch of sidescan sonar data for the lake bottom: as well as an interpretation of the imagery:

It turns out that the latter publication suffered from an unawareness of existing, pre-reservoir topographic maps. Nonetheless, their interps are good, but can be improved by evaluating the sonar image in conjunction with the historical map. Notably, the historical map is a detailed plane-table topographic survey by the USBR in 1939. It includes topography as well as some geological and ecological descriptions. Very handy. Combining these sources of data with my familiarity of the river in general and from 1939 aerial imagery of other, roughly similar reaches I can develop a map with reasonable confidence.  It is actually pretty helpful to have a good characterization of the river for interpreting the lower piedmont relations.

I am not yet finished with the terrestrial or subaquatic mapping, but thought I would share while I figure out a new blogging program (note that North is to the left in the maps):

DRG with draft Geolines

DRG with draft geolines including lake bottom lines

Historical Land Survey

Historical Land Survey with draft geolines and useful annotations.

Sonar image (not elevation, but return intensity)

Sonar image (not elevation, but intensity). Amazing stuff for a guy like me.

A colleague and I recently finished up the north half and you can check out the preliminary version here. I am now busily mapping away on the south half as well as the bottom of the lake.


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