Places Visited:
Idaho: Bruneau Dunes State
Park and Bruneau Canyon Overlook
June 7, 2007.
We are staying at Three Island Crossing State Park located in the town of Glynn's Ferry. $4 entry fee plus $21 for RV site with water & elect. Very nice campground and it is full. Mature trees with good shade and green grass. If by chance the campground at Three Island Crossing is full there is a nice commercial campground at a winery located at the front gate to the State Park. They were $20 for FHU and they had shade. Point being----they would be a good alternative and some would like it better than the state park since is was $1 cheaper and it had FHU.
After visiting Three Island Crossing State Park the second place we wanted to experience today was Bruneau Dunes State Park and Bruneau Canyon Overlook. Bruneau Dunes State Park just happens to be located 25-miles west of Three Island Crossing. Driving there is an interesting drive along the Snake River and through a beautiful agricultural area.
Bruneau Dunes is located in an ancient Snake River meander scar, known as Eagle Cove. The Snake River plain is a broad trench extending approximately 300 miles across southern Idaho. Volcanic activity was present for thousands of years. Lava flows occasionally dammed the Snake River canyon forming lakes which deposited large amounts of sediment that have become part of the sand supply for the dunes.
Bruneau Dunes is part of the southern Idaho semi-arid desert, a region of dramatic extremes, yet featuring a diverse range of plant and animal life. This area of Idaho averages only 7 inches of precipitation per year, with a normal summer temperature in the 90's.
The dune field of Bruenau Dunes is not large as dune fields go. Bruneau Dunes are located inside an old river meander scar surrounded by a much higher mesa on all sides.
This picture almost encompasses the entire dune field.
Eagle Cove makes a natural sand trap. Bruneau Dunes started to form approximately 11,000 years ago after the tremendous Bonneville flood. Bruneau Dunes is the tallest single sand dune structure in North America.
Ideal conditions existed here for sand dune formation:
A circular basin, carved by the Snake River, which forms a natural trap to catch wind-blown sand.
A supply of sand coming from ancient sediments laid down in the Snake River Plateau.
A wind blowing at least 10 miles per-hour to transport the sand granules.
Grains of sand in this dune field are all about the same size. Smaller sand continues on blowing while larger grains aren't moved by the wind.
We didn't spend much time in Bruneau Dunes State Park. It is a unique geological feature but it did not hold our interest for long. We are glad we saw it and would recommend anyone visiting the area to spend the time to visit the State Park and Visitor Center.
Our next adventure was to drive out to the Bruneau Canyon overlook 18-miles south of the small crossroads town of Bruneau
The first 5 or so miles out of Bruneau was through a well irrigated valley producing of all things ------------- alfalfa, and loads of it as this huge stack of alfalfa hay attests.
From Bruneau set your odometer on -0- then turn south on Hot Springs Road---there is also a brown sign pointing toward "Bruneau Canyon Overlook". About 10-miles down Hot Springs Road it turns into decently maintained gravel. When the odometer reaches 18-miles you should see signage for Bruneau Canyon Overlook where you turn right (west) one mile or so.
We have been driving down a gravel road for over 10-miles when low and behold we see the canyon overlook. It is hard to believe there is a canyon out here but here it is. From here one can see the dark gash in the earth.
Awesome, is the only word that comes close to describing it. Totally awesome! The Bruneau River has cut this canyon through what looks to me to be 600' of hard basalt. Some places are over 1,200' deep but I can't say for certain this overlook is over the portion of the 1,200' deep part of the chasm.
One can only imagine the cataclysmic events over thousands of years that created lava flow this deep.
By looking at the strata it is fairly easy to tell that tremendous volumes of lava would spill over this area then none would flow for hundreds of years. When lava was not flowing a layer of ordinary sediment would be laid down. Then lava would flow again covering the old lava and the sediments covering it.
In the picture on the left you can easily see the "bacon strips" clearly showing where the layers of sediment covered one old lava flow then that in turn was covered by yet another round of molten lava.
The section of Bruneau Canyon visible from the overlook is known as Five Mile Rapids. During the spring run-off, it is one of the most challenging stretches of white waer in the nation for rafters and kayakers.
While we can not see them, rhyolite canyons dominate the Bruneau/Jarbidge landscape. These canyons are noted for nearly contnuous, vertical, monolithic rock walls that rise directly from the river channel, and countless majestic rock spires, called hoodoos.
The basalt flows that stretch out from here were pushed up through large fissures in the earth's crust. As the flows cooled, they began to shrink and formed vertical fractures. This process is called columnar jointing.
Eventually, these colums of rock fractured again horizontally leaving large blocks. Eventually, the blocks break away and tumble to the base of the cliffs or into the river channel, constricting the river's flow and creating narrow, steep-gradient rapids such as those in the pictures.
The blocks of basalt that tumble to the base of the cliffs are known as talus thus creating talus slopes at the bottom.
This is a close-up of columnar jointed basalt.
In the picture to the right it is easy to see where layers of sediment were laid down between successive layers of molten lava.
I included this picture to show at least on thick layer of red sediment about 1/3 the way down this cliff face.
Evening around Three Island Crossing State Park is a good time to spot California quail. They are out moving around. During this time of year these birds are paired up. This is one colorful male, his mate is not nearly as colorful.
Evenings is also a good time to take pictures of the setting sun highlighting bluffs on the opposite side of the Snake River.
This is looking to the southeast across the Snake River from Three Island Crossing State Park in the late afternoon. So much of the geography in southern Idaho is lava rock. Surprisingly along the south side of the river is this large river cut of sedimentary rock.
Until next time remember how good life is.
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Mike & Joyce Hendrix
mikehendrix@isp.com