Recently accelerated erosion in the bed of Cache Creek testifies to a big change upstream: a switch in the drainage of Clear Lake. Photos by Andrew Alden

The rainy, dynamic terrain of the northern Coast Range features many rivers, but very few natural lakes. Any basins that may form by tectonic activity have short lives. Either they fill up with sediment, or rivers erode into them and they drain dry.

Clear Lake, by far the largest lake in the Coast Range, has sediments in it dating back some half a million years. The lake's basin never seems to fill with mud, although Clear Lake has always been shallow. Apparently something builds up the basin's sides whenever the lake outlet threatens to cut downward far enough to drain the lake dry. In recent geologic time, Clear Lake has drained eastward and westward at different times as one exit or the other has been plugged. You can visit both exits and glimpse the geologic evidence yourself.

Today Clear Lake drains east to the Central Valley down Cache Creek through a rugged canyon with high, steep walls. But biologists tell us that the fish of Clear Lake come from both the Russian River and the Central Valley. Without that clue, we might not make much of the straight little valley northwest of Clear Lake, just a few meters above the present lake level. Created by slow faulting, the valley holds some bits of water called Blue Lakes. What could have made Clear Lake drain in this direction?

Clear Lake shows signs of having drained northwest, through Blue Lakes, as well as southeast through Cache Creek, its current outlet.

The east side of Clear Lake is full of young volcanoes ranging in size from Mount Konocti down to a dozen little cones a few tens of thousands of years old. With that in mind it's easy to picture a large lava flow, or the emergence of a small cone, blocking Cache Creek and causing the lake to rise until it spilled through the valley of Blue Lakes to the Russian River.

You can drive up state route 20 from the north side of Clear Lake into this valley, and it's easy to picture it holding a river. Then the road hits a large bump, a hill right in the middle of the valley, and that seems to be the end of the line. But geologic mapping has shown that this is an ancient landslide.

The bare-topped hill blocking the valley past Upper Blue Lake is a landslide. The forested land in front is a younger delta fan.

A look at the topography here is instructive, and Google Maps' "terrain" setting is an excellent way to do that. The photo above was taken from the middle "20" symbol and the hill is marked with an asterisk.

Annotations: V symbols are delta-forming drainages, S marks landslides or possible landslides.

Notice how well-organized the stream drainages are leading down to the lakes. Each of the larger streams has built out a delta of sediment. But west of the lakes is an area of poorly organized, hummocky terrain that closely resembles the body of a landslide. It appears to me that the landslide nearest to Blue Lakes is the smallest and possibly the latest of a whole series.

The native tribes around Clear Lake have old stories of just such a landslide here. If we take them literally, that would place the event within the last few thousand years. The next thing to happen in this scenario is that Clear Lake would rise still further until it overcame the natural dam on Cache Creek and resumed its interrupted eastward drainage. In fact, there's no reason this should have happened only once.

But I mentioned visiting both exits of Clear Lake. Cache Creek goes into roadless country but on the other side, right where it meets state route 16, you can pull over at Cache Creek Regional Park and see this beautiful exposure, about 5 meters high, across the river.

From top to bottom its features are plain as day: a nice flat abandoned floodplain, a layer of coarse river rocks and gravel, the rugged profile of a former streambed, and the tilted bedrock of the Great Valley Sequence. In the typical river, the streambed is cut downward so slowly, only in the largest "hundred-year" storm events, that an exposure like this is never seen. But today's newly invigorated Cache Creek has cut through all this in one clean chop in just a few millennia.

Quest Educational Resources

 Print Guide - Lower Russian River

 Lower Russian River KML File

 Tips to get the kids in your life out into nature

 Designing an Exploration on Google Maps

Additional Links

• Russian River Watershed Council
• Bay Nature: Paddling the Russian River's Middle Reach
• Sonoma County Water Agency
• Stewards of the Coast Redwoods

California Coho Salmon are listed as federally protected,
and are critically endangered. Image: Richard James

As we would with any loved one, we care about its health and well being. Over the years we have witnessed wanton pollution from purposeful and "accidental" sewage spills, there has been gravel mining, seemingly unchecked agri-business dumping pesticides and sucking wells dry, and more than anything, precious water has been continuously pumped out and diverted to quench the thirst of the ever-growing populations of Sonoma and Marin Counties. Each one of these factors has taken some of the life and wildness out of the Russian River. And there comes a point when the natural world and The River does not have anything left to give.

Still there is the hope that nature is resilient. One of the best indicators of environmental health on the Russian River would be the return of the native salmon. While producing our story on these magnificent fish we had the privilege to witness the incredibly dedicated conservation fishery biologists at the Don Clausen Fish Hatchery at Lake Sonoma. Seeing them work gave me a lot of hope. These men and women literally hold the future of the coho salmon in their hands. Each egg is tenderly cared for– each little growing fish is carefully identified, numbered and individually tagged before being gently released into the wild. It is an enormous, time-consuming and laborious task. But without them, the critically endangered coho salmon have little or no realistic chance of returning to the Russian River.

Sadly, it seems that much of their work may have gone for naught. In early April 2009, for just one night's frost protection, the wineries of the Russian River valley went against a request by the National Marine Fisheries Service and turned open their taps, taking so much water out of the Russian River watershed that the water-table dramatically dropped resulting in a massive coho salmon die-off. It's another heartbreaking blow to an already perilous situation. The wineries were told specifically about the consequences of their actions last year at a special meeting held by the State Water Resources Control Board. Yet to protect a small percentage of an already glutted crop, the wineries knowingly risked dooming an entire species to extinction.

For more information see:

Quick drop in water level kills coho | The Press Democrat | Santa Rosa, CA
04/04/09
Frost protection measures to save crops stranded fish in Russian River tributary

Coho killed after water diverted to protect crops | SF Chronicle
04/04/09
Endangered coho salmon killed after a sudden drop in the water level…

I have always advocated for The Russian River and its small communities and businesses. I recommend it as the perfect getaway for friends looking for a weekend exploration. Hiking, canoeing, wine-tasting or exploring–The River is the place. In turn I have also regularly recommended and sought out Russian River wines. But I doubt I'll be recommending anything from this year's vintage. I have a feeling the 2009 Russian River wines are going to leave a very bitter taste.

Watch the California's Lost Salmon television story online.

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There is something about these rocks that draws you in. Maybe it's the way they jut out of the ground? Or perhaps it's the "Stonehenge" way they form an enclosed circle? Or maybe it's just a nice place to get out of the wind? Whatever it is, they seem to pull you towards them. And once you are there, they almost call out to be touched. The rocks, long known as the "Sunset Boulders," have attracted rock climbers for years. I've climbed these rocks before. But like so many other people, I had no idea I was touching history.

During the Pleistocene, 10 to 20,000 years ago, this place was very different than it is today, inhabited by massive mega-fauna; bigger elephants, lions, bears and wolves, than we see today. While those big animals went extinct thousands of years ago, they left their mark on this place.

Looking around these rocks it is easy for me to imagine the herds of Columbian Mammoths lumbering from the nearby wallow to rub against the boulders. I can picture huge herds of camel and horse grazing nearby. Yes, those animals evolved here in North America and then crossed into Asia where they thrived and survived. Weaving my way between the boulders, I can imagine how the predators could have used these rocks as an ambush site. I envision a huge saber-tooth cat slinking between the craggy rocks, looking to pounce on an unwary bison. I can see the prides of American Lion, similar but much larger than African Lions, basking on the tabletop boulders after a big kill. I can also picture the ultimate predator making their campsite here when that first hunting party foraged deeper inland. Yes, humans were here too. And I'm sure the same pull these rocks have today existed back then.

This seems like a sacred place to me. Sacred to history. So when you visit these rocks think about those who came before you. Think about the mammoth and the bison and the camel and the horse. Think about the lions, tigers, bears and wolves. And think about those first people. Tread lightly and respect this wonderful place. With care, these rocks will be here long after we all become part of history.

Special thanks to the San Diego Natural History Museum for contributing artwork and HD video to our story. Also, to see more artistic representations of Pleistocene mega fauna, by the artists who contributed to our segment, see:

Laura Cunningham's artwork

Artwork of Joseph Venus

William Stout's wonderful murals

Watch the Ice Age Bay Area television story online.