Rafting the Owyhee River—Oregon’s Grand Canyon

On April 10–14, we rafted the Lower Owyhee River in easternmost Oregon with Ouzel Outfitters (https://www.oregonrafting.com/owyhee-river). Because this part of the river is not dammed, and the climate is arid, there is only enough flow for rafting during the earliest part of the season. The droughts of the past few years meant that most trips were cancelled, as ours was last year (2022). We had signed up for the second week of April, but there was only enough water for one trip during the first week of April. On the other hand, this year was exceptional. With all of the winter snow, flows are expected to continue for weeks. Ouzel has booked this year through May and might even have a trip during the first week of June. The river’s difficulty is classified as Class III.

River basics

This hydrograph shows the river’s flow velocity in feet3/second (cfs) during the time of our trip (April 10–14). Notice that the vertical scale is not linear, so the increase in flow velocity was even more dramatic than shown by this curve. Warm temperatures on April 9 and 10 caused snow to melt in the river’s headwaters, and led to a rapid increase in flow velocity, from ~4,000 cfs on April 10 to ~8,000 cfs on April 11. That night, guides had to rush out to move the kitchen up-slope and prevent it from being inundated by the rising water. This increase continued on April 12, with the river reaching its maximum flow of ~17,000 cfs toward the end of the day. We were astounded by how quickly we were moving downriver. The guides were amazed too, as they had never navigated the river in such high-flow conditions. Temperatures declined drastically by Day 3 (April 12), causing melting in the headwaters to decline and the river’s velocity to slow. Nevertheless, by the end of Day 4 (April 13) the river was still running at ~11,000 cfs. Chart provided by Ouzel Outfitters.

Corridor of cataclysms

Kyle called the river a “corridor of cataclysms” because of the major geologic events that have impacted the river during the past 2 million years. The triad of cataclysms are (1) basalt flows that dammed the river for hundreds to thousands of years; (2) catastrophic emptying of glacial Lake Alvord when it topped its natural barrier and carried huge quantities of water and sediment into the river; (3) large-scale landslides that continue to cause large parts of the canyon walls to slump downwards toward the river, sometimes forming dams that block river flow.

Basalt flows. Four million years ago, before the river cut a canyon, basalt flows covered the region. Subsequently, the river began to cut downward and create an ever-deepening canyon. During this time, adjacent volcanic centers emitted numerous eruptions of fresh basaltic lava that flowed into the river and created natural dams that blocked the river’s flow and created lakes. The youngest eruption occurred just a few thousand years ago. Happily, the river is not currently blocked and visitors can marvel at the “cataclysmic” events that have impacted the river’s flow and shape.

On April 10 (Day 1). we saw thick basaltic lava layers overlain by inclined lava “foresets”. These foreset beds are unusual, in that they were formed by basalt flowing into water. Foresets are typically formed by sediments cascading down from the edge of a delta into a lake or ocean. In this rare case, basalt flows first dammed the river, then the lava continued to flow from right to left over the lava delta and cascade into the lake formed by the lava dam farther downstream. The level of the foresets is where the river would have been at that time, before it continued to cut down and deepen the gorge. Photo courtesy of Jay Ach.
Here is a closeup of the basaltic lava layers overlain by the lava foresets—the uppermost layers that are inclined in the downstream direction (toward the left side of photo). These foresets are least 10 meters (33 feet) high. Once the basaltic lava had dammed the river to create a lake, the continuing flows of basaltic lava interacted extensively with water. Evidence of this are the orange color of palagonite—an alteration product of basaltic glass— and the presence of pillow lavas—formed when lava is quenched by water—within the foresets. We could not see the pillow lava shapes from the river but relied on Kyle’s past observations. Photo courtesy of Jay Ach.

Spilling of glacial Lake Alvord. Throughout the west many lakes formed as the climate was transitioning from the last glacial maximum ~18,000 years ago. There are some small remnants, such as Summer Lake in Oregon, but most of these areas are now dry desert. Alvord Lake occupied the area between Steens Mountain and the Owyhee River. About 13,000 years ago it topped its sill and large quantities of water and sediment flowed into the Owyhee River and blocked its flow for some time. We floated past the Crooked River (see map at top of page), which was the tributary by which the water and sediment entered the Owyhee River.

This view to the west shows the flat Alvord Desert that was a lake until ~13,000 years age. On the horizon is snow-covered Steens Mountain that abruptly rises from the flat desert along a normal fault. The tiny settlement is Rome, where we entered the Owyhee River. This part of the river, visible on the right side of the photo, is wide and exposed, but as we rafted farther north on Day 1 (April 10), it became narrow, with steep canyon walls.

Landslides. Many places along the gorge are crumbled and chaotic because of landsliding. Parts of the canyon walls are rotational blocks that have moved downhill along slide planes.

We hiked uphill to get a better view of this jumbled landscape. The hills in this area are separated blocks that slid downhill and, in the process, were tilted backwards, away from the river (notice distant block on the east/left side of the river). The out-of-place slump blocks are a challenge to geologists working to figure out time and space relationships among the many rock units in the region.
Most of the landslides were too large to photograph. Here, though, we could see the whole thing. The gap in the ridge is where blocks mobilized and slid downhill. Jay is standing on jumbled rock pieces that slid down from the high ridge.

Other river images

This photo illustrates the complex geometry of geologic units in the canyon. On the left-side canyon wall is rhyolitic (silica-rich) lava that erupted from a volcano and covered the area before the Owyhee gorge was formed. On the right-side canyon wall is much younger basaltic (silica-poor) lava that flowed into the canyon after it had been created. Part of the older rhyolitic rock was eroded away by the river and later the basalt flowed into the canyon to create the observed inset layers. More of the older rhyolitic lava is visible higher up, above the basalt layers, on the right-side canyon wall.
Our second-night camp (April 11) at Jackson Hole. Jay is standing by our tent and our drying river clothes. Thick basalt layers adorn the top of the opposite canyon wall.
A beautiful rock sequence entitled “oreo cookie mountain” by Kyle, our geology guide. Photo courtesy of Jay Ach.
This photo shows an angular unconformity (indicates missing time) between the ~16 million-year old Birch Creek tuff (lithified volcanic ash) and the ~2 million-year old Bogus basaltic lava layers. The Birch Creek tuff was tilted before the Bogus basalt was erupted, producing the angular difference between the units. Photo courtesy of Jay Ach.
Our third-night camp (April 12) at Pinnacle, near the location where the trip usually ends on Day 5. The canyon is more open here, and on Day 4 we entered the Owyhee Reservoir. Our group was 12 clients (all from Oregon), 7 guides/staff, and Kyle, our geologic resource. Yes, it was quite cold at night, and even during some of the days. Photo courtesy of Ann Ames.
We saw large flocks of beautiful white pelicans. We also saw bald and golden eagles, a large variety of other birds, a river otter, and some antelopes. This view is to the north (downstream) in the Owyhee Reservoir.
Our fourth-night camp was at Black Rock with a natural hot springs that we greatly enjoyed, especially after the cold weather. This view is toward the south (upstream) along the Owyhee Reservoir. It was still low, but will probably fill, given all the water this year. Day 5 (April 14) was a lovely warm day, as we finished our paddle through the reservoir to our take-out spot. Photo courtesy of Jay Ach.

Native American art

Native Americans lived in this region for 1000s of years before European settlers disrupted their way of life. On Day 3, we stopped at the Hole in the Ground location to view petroglyphs scratched into the basaltic rock by native people. The patina is desert varnish, a thin red-to-black coating found on exposed rock surfaces in arid regions. The varnish is composed of clay minerals, and oxides and hydroxides of manganese and iron.

We could tell that this group of petroglyphs is relatively young, because the figures have not yet been coated by the desert varnish. We could only speculate about their meaning.
Figures in this group of petroglyphs were apparently created at different times because some of the glyphs are coated with varnish (e.g., some of the dots), whereas other glyphs are not. What was the meaning of these figures for the native people?

End notes

We were happy to experience the Owyhee River with unusually high-flow conditions, although the cold temperatures were a challenge. We’d like to go again, in lower-flow conditions, when the trip would be more leisurely, with more time for hiking. Taking photographs was difficult when on the water, and I lost my water-proof camera to the river on Day 2. At least I still had my phone! Thanks to Jay and Ann for contributing their photos.

And thanks to the U.S. Geological Survey (USGS) for funding Kyle to study this fantastically interesting part of the country. The USGS is chronically underfunded, which in my view is short-sighted, given how important it is for us to understand how our planet works.

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  1. Keeley Kirkendall on May 2, 2023 at 7:16 am

    What an awesome experience. Thanks so much for sharing your knowledge and pictures.

    • Landscapes Revealed on May 2, 2023 at 7:25 am

      Thanks for reading Keeley!

      • Maria Geigel on May 2, 2023 at 7:31 am

        Wow. Not just a gorgeous (pun intended) trip but incredible river-running experience. Yeah.

        • Landscapes Revealed on May 2, 2023 at 7:51 am

          It was gorgeous! (in both senses…)

  2. Rebecca Douglass on May 2, 2023 at 8:34 am

    It sounds like a great trip, and one for me to add to my list 🙂 (So let me know when you think of going again!). Great info, as always.

    • Landscapes Revealed on May 2, 2023 at 8:45 am

      Will do!

  3. Rebecca Douglass on May 2, 2023 at 8:43 am

    Bummer about the camera! (And did my first comment post? I don’t see it…)

    • Landscapes Revealed on May 2, 2023 at 8:46 am

      Comments must be approved by me! The camera was old; mainly I was sorry to lose the photos.

      • Kathy Mustard on May 5, 2023 at 6:20 pm

        Thank you for taking us along on your adventure Karen! We love Eastern Oregon and it it good to have another insight into this wonderful varied landscape!!
        Kathy and Tom Mustard

        • Landscapes Revealed on May 6, 2023 at 8:08 am

          Thanks Kathy, so glad you enjoyed the post!

  4. Earle Sloan on May 10, 2023 at 6:11 pm

    Great to have our first rate geologist on the scene. Thanks for sharing. Oregon geology never cease to fascinate me. I appreciate your having to put up with all the physical discomforts while we zoomers can sit on our couch and enjoy.

    Earle & Vanya

    • Landscapes Revealed on May 11, 2023 at 8:07 am

      I am really enjoying learning more about the geology of my new home state. Thanks for reading Earle and Vanya!

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