24-Nov-2000 -- The confluence is about a mile and a
half from the Oregon border, in the Owyhee Mountains. This section of
Idaho is where Columbia Plateau and the Snake River Plain meet. Here we
find the same granite formations found in the central Idaho Batholith,
evidently the last remaining fragments on this side of the Snake River.
We approached the confluence point from Jordan Valley. The valleys
are almost completely flat due to the basalt lava flows that once
flooded this area leaving just the mountain peaks standing free. When we
crossed the border back into Idaho we found the 4-wheel drive road that
took us toward the confluence, and drove about 1 ½ miles (of the
over 500 miles of dirt roads in the Owyhee Front) until we got out to
hike the remaining 1 ¾ miles.
At this point, we started climbing into what were probably once the
foothills of DeLamar Mountain. The mountains are being literally torn
apart by a number of basin and range faults that have been slicing the
mountains into blocks and pulling them apart.
We found the confluence close to the peak of the hills. The GPS gave
us a perfect lock and led us directly to it. You can easily see where
the hills have been sliced down the center leaving a couple of steep
valleys in between these hills and the bigger portion of the mountains.
It appears that the water from the confluence flows south and the
neighboring valley opens out toward the north, though they both flow
into the Owhyhee River.
We ate our lunch in the bowl near the confluence. Here you can see
fragments of basalt flows on the ridges. The soil ground consists of a
lot of rhyolte ash that had exploded from nearby volcanoes in gigantic
This area is the driest region in Idaho, being part of the high
sagebrush desert that covers Parts of Idaho, Oregon, Washington, Nevada,
and Utah. The road was very wet today however. During the day the snow
started to melt making the road very muddy. Getting back down the road
in our two-wheel drive pickup ended up being the difficult part of our
We saw jackrabbits, a deer herd and a variety of footprints of other
animals in the snow. The area is also very rich in minerals, of one the
best rock hounding areas in the country. There is an abundance of
jasper, opal, picture rock, petrified wood, quartz, and thundereggs. Up
at Silver City, not too far from here, they mined gold, and a lot of
silver from 1863 until just recently. The mine is no longer in
operation. This area is fascinating to explore. Most people think of
deserts as flat and dull. The high desert mountains here in Oregon and
Idaho are very exiting.
---(Geological information from Roadside Geology of Idaho by
David D. Alt and Donald W. Hyndman)