Two stunning geological formations in Central Oregon offer a wealth of insights into the beauty and complexity of these balancing or “ghost” rocks. Shaped by volcanic activity and erosion over millions of years, our resident “rock doctor” Dr. Kim Ely explains how the cliffs were formed, highlighting four distinct geological formations. Dr. Ely also gives advice on how you can find and visit these natural wonders of Oregon.
Transcript
Dirty Freehub
I’m Benjamin Purper, and today we’re talking about two fascinating geological formations in Oregon, the HooDoos and the Lake Billy Chinook Cliffs. I’m here with Dr. Kim Ely, a geologist and Dirty Freehub’s resident rock doctor. She’s here to give some insights into the formation, characteristics, and significance of these natural wonders.
Kim, thanks for joining me.
Dr. Kim Ely – The Rock Doctor
Thanks a lot, Ben. Good to talk to you today.
Dirty Freehub
So let’s start with the Lake Billy Chinook cliffs, which are these massive steep cliffs that stretch on for miles. Tell us a little bit about them.
Dr. Kim Ely – The Rock Doctor
Lake Billy Chinook is the confluence of the Crooked River, and Toluse River. In the 1960s, a dam was built just downstream of this confluence, and that flooded the canyons and formed a lake. So this dam is about 450 feet high and it’s the largest hydroelectric power dam that’s located entirely within Oregon.
The lake itself is about over 400 feet deep and there’s still 800 feet of canyon walls above the high water line. The canyons themselves have a pretty interesting history. First of all, they’ve been formed twice. So, the geological story of the canyons goes back 8 million years, which is not that long ago, geologically speaking.
But around that time, the High Cascades volcanoes started to form, and they erupted a huge amount of material, including lots of ash. A lot of this ash was blown to the east, where it was deposited in what is now the Lake Billy Chinook area. The volcanic deposits also included lavas from nearby volcanoes, such as the Round Butte, the development of the Cascade Range also blocked rivers that used to flow west, so they started to flow north. After the volcanic activity petered out about 4 million years ago, These rivers eroded their way down through all these volcanic sediments and formed the deep canyons. About a million years ago, what we now know as the Newbury Crater started erupting lava that flooded down the Crooked River before cooling and damming up and filling the Crooked River and Deschutes River canyons in the Lake Billy Chinook area with basalt.
The power of the water continued and the canyons were eroded again, resulting in the landscape that we see today.
Dirty Freehub
So what are some of the specific landmarks you’ll see if you visit Lake Billy Chinook?
Dr. Kim Ely – The Rock Doctor
Well, first of all, there are four distinct geological formations that you can quite easily pick out as you travel through the area. So the oldest formation and the most common to see as you descend down into the canyon are the thick volcanic and sedimentary deposits that I just talked about, including all the ash.
There’s also silt and river channel deposits. These are often light gray or pink in color. You see flat lying layers from either just a few inches thick through tens of feet thick. These rocks are known as the Deschutes Formation, and it has a total thickness of about 2, 000 feet. Then, the next oldest layer is what’s known as the Rim Rock Basalts, which overlie the sediments.
Away from the canyons, these have resulted in this, like, fairly flat landscape that, uh, you see before you get to the canyon edge. And along the canyon rim, you can often see that there’s um, columnar formations in the thick layer of basalt. And these columnar formations are also known as palisades, which is the source of the name of the state park here, the Palisades Park.
And as I talked about earlier, the first set of canyons was filled with basalt. So much of this younger basalt has been eroded away now, but you can still see it in some places. One example is the northern part of the narrow promontory that exists between the Deschutes and Crooked Rivers. There’s a 300 acre area there called the island.
This is all made of this, what’s called the intra canyon basalt. And on the eastern side of the Crooked River, there’s a place where you can see the younger basalt filling up a valley that had been eroded into the older sedimentary deposits. These younger basalts are usually dark gray or brown and are either massive in appearance or sometimes have columns like the brimrock basalts.
And even though these lava flows are much younger than the brimrock basalts, they sit lower in the landscape as they filled in the old canyon. Now the fourth thing to look out for is the youngest geological formation in the area, which are landslide deposits. These are now relatively old and they’re stable, but they can be recognised by seeing very chaotic arrangements of rocks and layers that have been tilted sideways.
And these deposits around the lake edge form the only sort of flattish ground within the canyon area, such as where the campground is.
Dirty Freehub
Yeah, do you have a personal favorite out of all these landmarks?
Dr. Kim Ely – The Rock Doctor
I think my favorite is definitely the layered volcanic deposits. There’s really detailed sedimentary features in there that are quite cool to look at and spectacular.
Dirty Freehub
So what can we learn kind of geologically from the Lake Billy Chinook cliffs?
Dr. Kim Ely – The Rock Doctor
So being able to read the rocks can tell us a lot about how our current landscapes have formed and understanding processes of how different rocks have formed or deposited tell us about how dynamic those landscapes were and still are today. So the volcanic rock tells us about the types of volcanoes that were active.
And whether they produce thin, runny lavas that flow up to hundreds of miles, or less runny, kind of sticky, clumpy lavas, or explosive products that layered the surrounding areas with ash. And sedimentary rocks can tell us a lot about past climates. In the case of Deschutes Formation, there are a lot of features that suggest deposition by water in sort of episodic, but really high energy environments.
Things like flash flooding, or spring melt coming off the mountains, that has put a lot of energy in and moved a lot of sediments around.
Dirty Freehub
All right, let’s turn our attention now to another really interesting landmark right by Lake Billy Chinook, and that’s the Oregon HooDoos. They’re sometimes called balancing rocks or ghost rocks. So Kim, what exactly are the HooDoos?
Dr. Kim Ely – The Rock Doctor
These formations used to be a bit of a secret. They were hidden in forest on steep hillsides, high above Lake Billy Chinook and kind of in a pretty out of the way place. But in the early 2000s, a fire swept through and burnt all the forest.
This revealed the Oregon HooDoos or the Metolius Balancing Rocks to the world.
Dirty Freehub
Can you describe what these things look like?
Dr. Kim Ely – The Rock Doctor
These are pillars, on an eroded, steep hill slope, and they often have little tops on them, which look like rocks balancing on top of a post.
Dirty Freehub
Yeah, they really don’t look like they should be able to balance like that, so how do they do that?
Dr. Kim Ely – The Rock Doctor
They’re kind of a um, take quite a special circumstance for these types of formations to be created. They tend to form in quite dry climates, like what we have here in Central Oregon.
They form by erosion, but very slowly. They require A geological situation where you’ve got a sort of soft, more easily erodible layer topped with a cap of harder rock. And so what happens here is the balancing rocks are protecting the pillar of softer material underneath from being fully eroded away. So they’re estimated that these rock formations are about 20, 000 years old, which seems quite old for something that appears so delicate and temporary. It’s our climate that allows them to be formed and maintained without high levels of rainfall that would quickly erode these sorts of things in other places. While we think of geology as being really permanent it’s actually a very dynamic system and things change all the time.
So formations erode and collapse, but at the same time, new formations form. And so as part of that area where the HooDoos are, it’s as the cliff and the steep hill slope erodes back away from the lake new HooDoos could form in the future.
Dirty Freehub
How can people go see the HooDoos?
Dr. Kim Ely – The Rock Doctor
They’re actually now pretty easy to see. There’s a place called the Balancing Rocks Overlook, which is a short half mile walk from a junction on Montgomery Road in Culver. Alternatively, if you’re on your bike and you don’t want to walk to see the HooDoos , just go down the road, down the hill, past the trailhead and look out to the north. You can see the HooDoos there.
Dirty Freehub
All right, well, I’ve got to make my way out there to see this stuff. Kim Ely, thanks so much.
Dr. Kim Ely – The Rock Doctor
Great. Thanks a lot.
