I took the photo of geos walking up the bulldozer road while looking straight into the sun. The almost blinding light from the sun peeking through clouds and gleaming off the numerous glassy shards and fragments of rhyolite lying on both sides of the road generated numerous lens flare spots—partly because I need a new camera! Although the effect doesn't look too bad, it was difficult to get useful pics in this direction (almost due south).
The location I've given at the end of the post is the start point of our hike (also see the embedded Google Map just above that, which shows the entire hike route). We had driven west from S.R. 139 on a paved road that is variably called County Road 97 or USFS service road 97, then we turned right onto USFS 44N01. After about a mile and a half, we turned left onto the Glass Mountain Pumice haul road, which was inactive at the time: the pumice mine doesn't operate year round. I don't know if this road is really open to the public, but signs on the road said, "Watch for Trucks," not "Keep Out."
|Looking eastward from the bulldozer road at a roundish mass in the blocky rock of the northernmost dacite flow lobes, .|
Here at Glass Mountain, many of of the blocky pieces and fragments at the surface of the flows have broken during flow formation or during later physical weathering. Breadcrust texture, if present on this rounded mass, for example, would indicate that this particular surface might be an original flow surface: the surface was molten hot, then it cooled enough to form a crust, then it cracked because the interior was still hot and expanding. I'm not really sure, however, if we're really looking at breadcrust texture.
|The blocky surface of the northernmost dacite flow at Glass Mountain, with what appear to be pressure ridges or ogives.|
|Google Earth image of the northernmost part of the rhyolite-dacite contact area. Magenta marks the contact; a few flow lines or ridges are in cyan.|
|Chunk of black obsidian with reddish oxidized (and partly devitrified?) bands.|
|Vesiculated obsidian (pumice or "puffed obsidian", AKA pumiceous lava flow rock, part of the rhyolite flow rather than tephra) at the end of our hike (Google Maps location).|