Tuesday, February 26, 2013

Geo 365: Feb. 26, Day 57: A Last Lingering Look

Before driving the dirt road up to the edge of Table Rock, we pulled off the pavement to get a last lingering look at the very northern edge of Oregon's Basin and Range in this area. Picture Rock Pass, which I mentioned yesterday, and at which we didn't stop (we missed the pull-off, visibility  is poor, and starting downhill, traffic is picking up speed, so I didn't feel like it was sensible to try to go back), is the notch on the horizon to the right.

The nature of termination of Basin and Range varies from place to place in Oregon. In this area, the faults get lost under either younger volcanics (such as Table Rock, on the left edge of the photo), or Pleistocene pluvial sediments (such as Silver Lake, the basin along the line of sight in the photo to Picture Rock Pass). North of Table Rock is the Fort Rock-Christmas Lake Valley, which I think is more properly described as a tectonic basin, but it isn't of the Basin and Range style. It's elongate in an east-west orientation, rather than north-south, which is the standard for Basin and Range.

The last paragraph of this post does a pretty good job, I think, of introducing the nature of Basin and Range's termination against the Blue Mountains across Oregon's High Lava Plains- the latter being the proper name of that physiographic province, not simply a physical description. It's a topic I hope to get back to, and will have plenty of opportunity over the coming days, as I expect to continue this day's photos for a while. In case you hadn't noticed, everything over the last week, since Monday, Feb 18, was taken on the same day. In fact that first photo at Abert Rim was taken only 3 1/2 hours earlier than this one, and well more than half that was spent at stops, not driving. A quick check on Google says that Valley Falls to Silver Lake is an hour and 17 minutes drive time. Valley Falls is a bit closer than the Abert Rim pull out, and the community of Summer Lake is a bit farther than Table Rock, so that's a good approximation. There's a heck of a lot of fantastic geology packed into this drive, and few take advantage of it.

Photo unmodified. August 20, 2011. FlashEarth Location. (Aside- I generally have a very good "location memory," and I have taken a fair amount of pride in putting the cross hairs within, literally, a few feet of where I was standing when I shot the photo. In this case though, I know there was a wide berm on the east side of the road, but I don't recall exactly where we were. So the cross hairs are on a wide berm in a spot that looks like it has about the right geometry for the above photo.)

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