Friday, March 13, 2009

Friday Fault Photos #12

Just a quick post showing some photos I took from the air while flying back from Alaska. These particular photos were snapped over south-central Oregon, about 25 km south of Christmas Valley and about 20 km northeast of the north end of Summer Lake, pretty much out in the middle of nowhere.
The photo above zooms in on a linear structure, which is highlighted in part by snow and which appears to be a small-offset fault cutting through some layered, probably basaltic volcanic rocks. We are looking about due east. The steep-sided, northeast-facing wall running parallel to the fault (facing away from us and not seen in the above photo) is part of the Diablo Rim, about 5 km northwest of Diablo Peak, near Diablo Flat and Murphy's Lake (MSRMaps location).
Stepping back a little and looking at the area from a slightly more northerly angle - that is, looking about ESE - that same fault is in the lower right of the above picture. This photo also shows the really nice alluvial fan that comes out of the mouth of Sand Canyon.
Here, we've stepped even farther back, looking at a larger area from the same angle as in the last picture. Numerous linear features can be seen in the foreground and background. These features include the uplifted and tilted edges of basalt flows, which are cut by faults running north-south, northeast-southwest, and northwest-southeast.
The linear nature and locally rhomboid shapes of the faults and flow edges are accentuated somewhat by this low-angle Google Earth image.

7 comments:

Lockwood said...

This is exactly why I always try to get a window seat when I fly (not much lately). These are some great pictures! The rock in this area is mostly Steens Mountain Basalt, which is quite similar to the Columbia River Basalt in age and composition, but smaller in volume and areal extent, and extruded in a more southerly eruptive area, as the name implies. I've been up and down route 31 more times than I can count, but I've never made it to the other side of that basin. And re the alluvial fans- many of these underwent significant growth during the time of Pleistocene pluvial lakes, and are more deltaic in nature than fan-like! Nice piece, thanks!

Diane C. said...

Cool aerial photos showing linear features and an alluvial fan. Not something I see everyday; fascinating post!

Unbalanced Reaction said...

Nice! I can't contribute any geo-speak... but I do know the pictures are pretty!

Maple Leaf said...

Wow. Pretty amazing shots. :-)

Silver Fox said...

Lockwood, I'm glad you could add some info about the geology. I was tempted to say these were of Columbia River Basalt origin or related to them, but I really didn't know for sure. I used to drive route 31 quite a bit to Sisters (well, once a year and back), then took to going up through K-Falls. I've never been across the valley, have been around Christmas Valley some, and have seen a measured section of Pleistocene-Quaternary lake beds in Summer Lake.

Interesting about the old lake deltas - they look quite sandy from the air.

Silver Fox said...

Diane, glad you enjoyed the sandy deltaic fan and photos.

And likewise, thanks UR and Maple Leaf.

Silver Fox said...

UR, in order to contribute to the geo-speak, you need to say profound things like - wow, faults are cool! - and things like that. :)