To validate this cache answer the following questions.
1. Your name and who is in your party.
2. Which hill is the tallest?
3. Are leading edge prows about the same angle for the two largest hills?
4. Do all the hills share the same general shape or do you find one different (ignore the sizes). If one is different, describe what is different.
5. Do you think the water covered the hills? What is your reason for your answer?
6. Cachers love pictures but do not post pictures of the hills.
ARMADA OF HILLS
After a cold long winter of cabin fever I like to drive the Palouse to see the beautiful rounded green hills of winter wheat. The further west I drove I found some of the hills became weird looking. One spring I drove by these 3 hills and wondered what caused them to be shaped the way they are. I never would have thought of a huge flood shaping them.
In John Soennichsen’s book BRETZ’S FLOOD, he told of Bretz’s 1922 trip to the Palouse area. Soennichsen related that Bretz was observing the hills below Cheney and noticed the long narrow shape that were steep slope and faced north. Bretz recognized the hills bore a striking resemblance to ships bottom—long, narrow, and with two sides coming together at the northern end to form A-shape prows almost like those of an battleship. Bretz called these hills “Palouse Islands”. Now they are called streamline hills As with the giant ripples, Bretz recognize the only thing that was capable of forming these hills would be a giant flood. The hills added one more piece of evidence for a catastrophic event.
You must know the composition of the hills to understand how the flood shaped them. The bedrock is basalt formed by multiple lava flows of which the last flow was 6 million years ago. The basalt was then covered by pebbles and gravel and finally covered by loess . Loess is a fine-grained accumulation of clay and silt particles that have been deposited by the wind. Current research shows the loess being blown in from the Pasco Basin and the Walla Walla Valley. Depth of the material above bedrock can be a few inches up to several hundreds of feet. When basalt cools it shrinks and has many cracks and crevices which allow the flood waters to tear (pluck) out large chunks of rock at a time forming the coulees in the scablands. The loess was not as easily eroded and some hills survived the many floods that washed around and above them.
What caused the peculiar shape hills? Imagine a typical gentle sloping and round domed hill being a washed by a large flood. First the water will be deflected up over and around the hill but when it does the water will speed up due to the water pressure pressing from behind. As the water leaves the hill and hits the main stream flow it will erode all edges of the hill. The first to be eroded is the part of the hill closest to the ground and the front and top of the hill because that is the thinnest part and is more directly in the flood path. The water is also bombarding the hill with ice bergs, boulders and rocks which gouges out more of the hill. The center part of the hill has more mass and is slower at eroding. As the hill continues to erode around the edges, it takes on the shape of a ship hull or an airplane wing. This is the interesting part. The shape you see is Mother Nature shaping a hill so that it becomes very aerodynamic which allows the water to flow around the streamline shaped hill with minimum drag and erosion. Flood after flood may erode the hill more but the shape should stay about the same only in a smaller scale. Surely some hills did erode away completely. The hills that were not covered completely by the flood would have a more dome shape top rather than the pointed shape.
Notice the shape of the largest hill and you will see the leading edge slope up very rapidly to the peak and slowly decrease in height to the tail. When you drive up to or leave the parking area, look at a hill almost straight on. You should see the side of the hill start at a point and rapidly widen and then slowly narrow to the tail. The widest part of the hill and the peak is usually the same because of the aerodynamic flow. There are streamlined hills on Mars in which Vic Baker has studied from NASA’s pictures and has formulated the shapes of the hills both on Mars and Earth are about the same. The only way Mars’ hills to have formed is by moving water and when we land we may be able to find water on Mars. Vic Baker has determined the length of the hill is about 3 times its width.
Bretz’s took graduate students as helpers and his wife as cook on his many trips to the scablands. Bretz would borrow his wife’s colander and sift loess as he climbed a hill. When he found the break between the flood debris and the old loess he could determine how high the flood was on the hill or whether the flood covered the hill completely. Some hills may have a depression at the start of the hill from the water being forced down and a seasonal pond may be apparent or maybe the grass is greener. Most however have been filled in from erosion of the hill or loess blowing in. Over time loess has covered enough of the hills to grow plants and yet they are not as lush as the eastern part of the Palouse hills. The streamline hills lie in the rain shadow of the Cascade Mountain and do not receive adequate rain to grow crops and only have native plants cover them.
REFERENCES
On the Trail of the Ice Age Floods by Bruce Bjornstad
Bretz’s Flood by John Soennichsen
http://adsabs.harvard.edu/full/1978LPSC....9.3193B