Geologist John Bush is a professor emeritus at the University of Idaho. He has spent most of his adult life in and around the geologic underpinnings of the Palouse.
What is the problem that the Palouse faces with water?
It's already become a center of tension: how much water do we have or don't have? Should we allow more use or not? In any case, what's really hard to predict is when we're going to reach that point where we'll have to slow down development. From my experience in the area, it could be 10 years, 15 years, 20 years, 50 years. Someday it's going to affect the development in the area, because we are using more water than is getting into the system.
This is not a problem of farmers using the water, is it?
Someday it's going to affect the development in the area, because we are using more water than is getting into the system.
And then there are issues of people wanting to come here and develop a factory or some business that would use a lot of water for their business. Actually, that's where the issue is it's not with the farmers. They don't use that much water.
How have you come to understand this aquifer?
The Grand Ronde comes from the basalts that are carrying the water. So both cities, both universities are heavy users out of the Grand Ronde. All of Pullman is out of deep aquifers. Moscow does have a second aquifer which is a shallower one; and that is what they are drilling here today; and they are drilling in the shallow aquifer. The deeper ones are 800 to 1400 feet deep.
So Moscow actually has two aquifers that we produce a lot from both the shallow one and the large one. We know the shallow one can¹t sustain it. It's already been pumped down in the late fifties, early sixties where it provides about 30% of our city water into Moscow; and all the domestic wells that are out in the countryside are generally out of that shallow aquifer here in Idaho. So those are the two main aquifers.
There are little shallower aquifers that may or may not be contributing to the deeper ones. They're just beneath the Palouse soil in sediments which overlie the basalt. One of our monitoring wells will be in those sediments. So really three aquifers, only two that we use.
If... we get a rain storm here and dust is in the air, it will actually rain mud. And that shows you the process is still going on.
Give us a quick thumbnail description of what's under this soil.
The most exciting event to me is that if we look at this area as being developed pre-volcanic event, it's very steep topography. The way we know that is that the wells in Moscow are 1400 feet deep in volcanic rock. In Pullman they're 2200 feet deep. So, if we were here before the volcanism, we would be standing in a canyon that is 1500 feet below where we are now, looking up at Moscow mountain. So it's just a tremendous steep topography.
In Pullman you'd have been 2200 feet, almost down to sea level, looking up at these higher buttes around.
Then what happened was about 17 million years ago, there was a large volcanic event that occurred primarily to the south of here, the Grand Ronde area to Junction, Oregon and Idaho and Washington. It was a large volcanic event, sort of a series of fissures that fed large massive flows; and it's one of the unique places in the world. They're called flood basalts.
They're volcanic flows that came out just south of us, south of Lewiston. But those flows flow all the way to Wenatchee, to present day Pasco, present day Portland, but they sourced out just to the south of here. The flows went basically towards the west but also came in and filled up that huge canyon. We're talking about that 2,000 foot canyon. These volcanic events started 17 million years ago and ended about 14 million years ago, filled up that 2,000 feet of material which is our present day aquifer.
What is fascinating geologically is that's a really short event and a lot of volcanism. I know to some people, well, that took two million years, but geologically, when we look back on the record, that's a major volcanic event; and even though we don't see the exposures here, you can drive just to the south along the Snake River, and you can look in and see sort of a cross-sectional view of what is underneath Moscow. So you go down to Lewiston, go down to the Snake River, and you can see these layers of volcanic flows which are underneath aquifers.
What is it that surprises students the most when you describe this geology to them?
Then you realize, that's a heck of a large canyon. And I think that surprises people the most.
And there is lots of interesting geology in the subsurface, too. There are 700 feet of sediments that are inner-bedded with those basalts. The surprise is, you don't think that when you look out here, and you see the loess. Paul McDaniel would be disappointed if I said this, but to the geologist they want that soil stripped off so you can see the rocks, and he likes to look at the soil. They're surprised by that amount of geology that is in the subsurface and its geologic history, that it's tied to the huge volcanic events out here in southeastern Washington. I think that's generally a surprise.
As you drive from Grangeville to Lewiston, some might say that area is also the Palouse. Is it?
So the rolling part of the hills is primarily the way the bedrock was. The soil is very thin. Here, you can look around and some of the loess is 100, 150 feet thick. The rolling hills owe their origin to not just that the rock is irregular, but also to the windblown loess coming in. The plateau by Grangeville is the same geologic setting, but it doesn't have that thick soil.
Did the creation of the Palouse loess soil have something to do with the Missoula flood of thousands of years ago?
So you carry the material into this area. You get volcanic ash mixed from the Cascades at times. You get dust picked up from Pasco, but it's also going across what we call the flood sediments Missoula or Spokane flood sediments, out in the Columbia basin. That's where the fines are coming from.
If you're ever in Moscow in a rain storm after a dust storm, that process is still going on, because what will happen here is it will rain mud. If you happen to get that coincidental time when there has been a huge dust storm out of Pasco, we get a rain storm here and dust is in the air, it will actually rain mud. And that shows you the process is still going on.
Explain the role of the Missoula floods in the creation of the Palouse.
But when the Missoula flood stripped the soils, didn't the winds eventually bring that soil to the Palouse?
All this makes the Palouse geology truly unique, doesn't it?
Because of research done over in the Pasco area where our nuclear waste has been buried at times, we know more about the basalts in this area than any place in the world. For example, just north of us here, you could take those chips up, those little broken up pieces of basalt and take them to the lab and analyze them chemically and know what flow you were in. The area had 125 or 150 flows, and the fact that we have the ability to get a handful of chips from a well and correlate that flow to the other ones, well, geologists from all over the world come here and go on field trips.
We just had one two years ago called the Goldsmith symposium and there were 2,000 people who came here and stayed here and one of the main things was a symposium on the Columbia basalts. So that's unique in the volcanic part.
Then we got that loess sitting right on top of the basalts. The last large basalt flow was about 14,500 years ago, and then we look out here. This loess, which is the oldest at about 2 million years, sits right on top of that.
So you've got two unique events in geologic history documented right here. The two major geologic events were really the volcanic event that filled in these huge canyons, and that is called the Columbia river basalt group, and they are a sequence of basalts and sediments. Here they're 2,000 feet thick beneath Moscow and Pullman. That's the first event.
And then we sort of have a hiatus, a break between the last major volcanic flow and then we get this sequence of wind blown, wind deposited loess which was deposited itself, four major events in the last two million years.
Those are the two things which really are the most fascinating part about the geology.
Do you see any major changes in the Palouse, geologically speaking?