Ancient Lake on the Eel River

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Science magazines are abuzz with the news that there was a 30 mile lake on the upper reaches of the Eel River around 20,000 years ago. It was caused by an enormous landslide. The lake occurred East of Harris and is estimated to have lasted around 1,000 years.

According to the California Institute of Technology news release,

“Perhaps of most interest, the presence of this landslide dam also provides an explanation for the results of previous research on the genetics of steelhead trout in the Eel River,” says Mackey, referring to a 1999 study by the U.S. Forest Service. In that study, researchers found a striking relationship between two types of ocean-going steelhead in the river—a genetic similarity not seen among summer-run and winter-run steelhead in other nearby rivers.

An interbreeding of the two fish, in a process known as genetic introgression, may have occurred among the fish brought together while the river was dammed, Mackey says. “The dam likely would have been impassable to the fish migrating upstream, meaning both ecotypes would have been forced to spawn and inadvertently interbreed downstream of the dam,” he explains. “This period of gene flow between the two types of steelhead can explain the genetic similarity observed today.”

Once the dam burst, the fish would have reoccupied their preferred spawning grounds and resumed different genetic trajectories, he adds.

“The damming of the river was a dramatic, punctuated affair that greatly altered the landscape,” says coauthor Joshua J. Roering, an associate professor of geological sciences at the University of Oregon. “Although current physical evidence for the landslide dam and paleolake is subtle, its effects are recorded in the Pacific Ocean and persist in the genetic makeup of today’s Eel River steelhead. It’s rare for scientists to be able to connect the dots between such diverse and widely felt phenomena.”

The lake formed by the landslide, researchers theorize, covered about 12 square miles. After the dam was breached, the flow of water would have generated one of North America’s largest landslide-dam outburst floods.

Other stories on this lake have come out here, here, and here.  Some of the science behind it can be found here.

Map indicates general area of Lake. The slide that blocked the Eel came from Neafus Peak.

UPDATE: The North Coast Journal has a nice piece about this.  See also this.

UPDATE: and this.

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16 comments

  • Wow, thank you for posting this Kym! I’m so excited to go read the rest of the articles, I love stuff like this!

  • Wow, thank you for posting this Kym! I’m so excited to go read the rest of the articles, I love stuff like this!

  • I have read that Clear Lake was formed by a landslide so large that the water began draining to the east out Cache Creek before the lake could break through the landslide. Can’t cite the article.

    • Yep…the two Blue Lakes west of Clear Lake on hiway 20 used to be part of Clear Lake. The lake drained west into the Russian before an eruption and slide cut off the route.

        • Mt. Konocti is a dead or dormant volcano, when you drive by on HWY 20 you can see where the North East side of the mountain blew out one time and created the peninsula that sticks out farthest North of the mountain. Off the shore of Soda Bay there is a hotspring rock outcropping that, until recently, was built into a pool/hot tub. We used to go soak in the 100 degree hot tub, but the retaining wall was taken down a few years ago. The hot, sulphur water is still there, turtles lie on the rocks sometimes. It’s beautiful. But you can tell there was an eruption some time ago, the heat is still there.

      • From one of the articles you posted:
        “The (Clear Lake) basin is located on a topographic divide between the Russian River system to the west and the Sacramento Valley to the east. The lake initially drained to the Sacramento River, then into the Russian River, and currently drains into the Sacramento River. The change in drainage is thought to be primarily due to the faulting predominant in the Coast Mountain Range, although other forces have played a part in Clear Lake’s history. For instance, the basin’s outlet to the Russian River was blocked about 10,000 years ago by a landslide immediately west of Blue Lakes. Blue Lakes now exists in the flooded outlet canyon.

  • I have read that Clear Lake was formed by a landslide so large that the water began draining to the east out Cache Creek before the lake could break through the landslide. Can’t cite the article.

    • Yep…the two Blue Lakes west of Clear Lake on hiway 20 used to be part of Clear Lake. The lake drained west into the Russian before an eruption and slide cut off the route.

        • Mt. Konocti is a dead or dormant volcano, when you drive by on HWY 20 you can see where the North East side of the mountain blew out one time and created the peninsula that sticks out farthest North of the mountain. Off the shore of Soda Bay there is a hotspring rock outcropping that, until recently, was built into a pool/hot tub. We used to go soak in the 100 degree hot tub, but the retaining wall was taken down a few years ago. The hot, sulphur water is still there, turtles lie on the rocks sometimes. It’s beautiful. But you can tell there was an eruption some time ago, the heat is still there.

      • From one of the articles you posted:
        “The (Clear Lake) basin is located on a topographic divide between the Russian River system to the west and the Sacramento Valley to the east. The lake initially drained to the Sacramento River, then into the Russian River, and currently drains into the Sacramento River. The change in drainage is thought to be primarily due to the faulting predominant in the Coast Mountain Range, although other forces have played a part in Clear Lake’s history. For instance, the basin’s outlet to the Russian River was blocked about 10,000 years ago by a landslide immediately west of Blue Lakes. Blue Lakes now exists in the flooded outlet canyon.

  • I always wondered about this subject. Thanks for all the great info.

  • I always wondered about this subject. Thanks for all the great info.

  • Still happens…..remember that slide in 1998 (or 1997?) past Redway north that blocked Redwood Drive AND the river for a few weeks?

  • Still happens…..remember that slide in 1998 (or 1997?) past Redway north that blocked Redwood Drive AND the river for a few weeks?

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