Moses Lake
Sand Dunes and Sage, O' My!
2010 Middle Distance Championship Venue in Eastern Washington
A field laboratory for catastrophism
by Don Atkinson and Mike Schuh, Cascade OC
The four venues for the June 2010 US Orienteering Championship events – Middle, Long, Sprint, and Trail O' – were shaped by the same major geologic events, yet are very different from each other. They offer four days of diverse orienteering.
In his article in the November-December ONA ( see below ), EWOC member John Harbuck described how the catastrophic floods from the ice dammed Lake Missoula shaped the terrain of Eastern Washington during the ice ages. Most of the channeled scabland landscape, like that around Fishtrap Lake, the site of the Long Distance Championship, hasn’t changed much since the floods. However, Potholes Sand Dunes, the venue for the Middle Distance Championship, has been further modified by major geologic forces.
Eastern Washington is in the rain shadow of the Cascades Mountains and annual rainfall ranges from just below ten inches per year in the middle part of the region to the mid twenties as the terrain starts rising in the foothills of the Rockies near the Idaho border. Portions of the region are classified as desert.
After the last flood at the close of the ice age, between 15,000 to 12,000 years ago, erosion was slow and soil built gradually in the channels allowing a thin forest cover to be established in the higher rainfall areas. This is what happened at Fishtrap Lake and Riverside State Park (Trail O' Championship and junior training camp venue), creating a sparse Ponderosa pine forest that is open and thus allows very fast running.
In the areas that were not eroded by the flood waters, the wind deposited loess soil became bunch grass prairies which, with the advent of paddle steamers and railways to take the product to market, were cultivated to become the wheat fields of the Palouse (primarily closer to the Idaho border, where there is more rainfall).
However, the semi-desert area near Moses Lake had to wait for another development. It was too arid for wheat cultivation, and sand dunes covered some parts of the area, sage brush others. Some small scale privately funded irrigation schemes were built close to rivers, but most of the land remained unclaimed, in federal ownership.
Then, in the depths of the depression of the 1930’s, Franklin Roosevelt promoted the Grand Coulee dam project as a stimulus scheme that would provide lasting benefits in the future in the form of low cost hydroelectric power and irrigation of a huge area of semi-desert land. The dam was completed before World War 2, and the power generation arrived in time to produce aluminum for thousands of aircraft for the war effort, but the irrigation was phased in mainly in the 1950’s. This is the federal Columbia Basin Reclamation Project.
Which brings us to the Moses Lake – Potholes Sand Dunes Map to be used for the US Middle Distance Championship event. This area is completely different from the Fishtrap Lake area and Spokane's Camp Sekani (Sprint Championship venue). Sand, from the Columbia River 30 miles/50km to the west, covers the area with dunes, some 15m high. These dunes bury all signs of the eroded, channeled basalt. The only visible hint of the obscured channel is the slight, ca. 20m rise in topography just east of the competition area – this is the buried eastern edge of the local channel. The other side of the channel is about 6 miles/10km to the west and is easily discernible in aerial photos. Approaching Moses Lake from the west on I-90, cresting this scarp at about milepost 168 provides an expansive view of the Moses Lake area. Recall that during the floods this entire 6-7 mile wide channel was full of water, albeit for only a few days at a time...
As if being inundated by the Missoula Floods and then buried by sand wasn't enough, the area was touched by yet another catastrophic geologic event – the 1980 eruption of Mt. St. Helens. The ensuing ash fall covered the Moses Lake area with about 2 inches/4cm of ash (which actually is very fine grained rock, not ash). This light-colored layer is readily visible here and there in the competition area; in most places it has since been buried by as much as a foot of sand. The amount of sand movement in the last three decades and consequent vegetation growth thus can be seen quite clearly. Truly, the venue is a fascinating outdoor geology and natural history learning experience.
When Potholes Reservoir was filled behind O’Sullivan Dam, the partially drowned dune peaks formed a myriad of small islands in the reservoir. As the water table has risen over the years since the start of irrigation, the dunes on the adjoining lands have become vegetated with grass, sage and a few small trees. The dunes are now mostly locked in place by the vegetation (they continue to move, but very slowly), and the map has a complex network of hillocks, depressions and ponds. There is very little open sand - most of the area is covered with scattered sage and grass (like Fishtrap, this is fast terrain). With numerous small cattail marshes and an occasional willow thicket, the area is now home to a diverse collection of wildlife and waterfowl.
The generally level mapped area is bounded on one side by the reservoir and on the other by the Moses Lake Off Road Vehicle area. This seems to be the modern equivalent of the wild wild west, with a large number of ORV enthusiasts camping out there with a minimum of rules and regulations, doing their thing with their rigs, turning that part back into desert, almost completely devoid of vegetation.
The Potholes name comes from some roughly circular depressions eroded by eddies in the flood waters back in the ice age era. Just downstream (south) of O’Sullivan Dam there is an area of small lakes and potholes and relatively unmodified erosion channels – and, of course, beneath the sand dunes.
An excellent source of more information on the Missoula Floods is the Ice Age Floods Institute.
Fishtrap
by John Harbuck
This geologically unique area is one of only a handful of sites in the world
where the terrain was sculpted by immense floods. During the last ice age,
about 15,000 to 12,000 years ago, the Purcell Lobe of the great Cordilleran
Ice Sheet moved south from Canada, blocking the mouth of what is now the Clark
Fork River and forming Glacial Lake Missoula in western Montana. When the lake
reached about 2,000 feet in depth (with a volume as great as Lakes Erie and
Ontario combined) the seal at the bottom of the glacier was broken, channeling
beneath the glacier expanded exponentially, and the entire lake--about 500
cubic miles of water--drained in two to three days across eastern Washington
and down the Columbia River Gorge. This flow was ten times the combined flow
of all the rivers in the world. The glacier continued to advance, reblocking
the Clark Fork valley and reforming the lake. This cycle of filling then
outburst-flooding occurred probably more than sixty times.
One might expect rather a bit of erosion.
Our new Fishtrap Lake map, where the 2010 US Long Course Championship will
take place, shows this erosion. A long narrow lake with steep basalt lakeshore
cliffs divides the area. Most of the area is open grassland with patches of
ponderosa pine and aspen. Basalt outcrops are numerous, some as linear cliffs,
some sculpted into intricate canyons containing odd perched depressions,
ponds, marshes. Pothole ponds pepper the area, providing nesting for numerous
waterfowl. Mule deer and coyotes are abundant. And for the arboriphiles
(especially those in the East), many of you will get a chance to punch a
control beneath a mature American chestnut tree.
Camp Sekani
by Mike Schuh
Like the other venues to be used this coming June, Camp Sekani was shaped by the Missoula floods. As the flood waters raced through the Spokane valley, they picked up anything that wasn't fastened down – and a lot that was. The hillsides on either side of the valley's narrowest point – Camp Sekani on the north and Dishman Hills on the south – were stripped clean. Unlike the other venues, the floods exposed very old metamorphic rocks instead of the much younger basalt common elsewhere in eastern Washington. These very resistant metamorphics form the very durable rock features of the park.
In the intervening 12,000 years since the floods, some soil has developed, but not much. Some of the bare rock has eroded to fill in some of the gullies and to cover a few of the slopes, and this supports the pines, some smaller shrubs, and grass. There are very few thickets, and no water features (well, except for the abandoned water faucets from the former Boy Scout camp...). Neither are there fences, paved roads, nor flesh-ripping thorns. There is, however, a totem pole.
Camp Sekani is crisscrossed with trails, most of them created and maintained by mountain biking groups. Today the park is a popular mountain biking area – a quick search of YouTube will yield videos of races that have been held there. In several places there are jumps, many of them providing for some serious hang time. The mountain bike community has also built some obstacle courses to help bikers develop their skills.
From Wikipedia: http://en.wikipedia.org/wiki/Missoula_Floods
The Missoula Floods (also known as the Spokane Floods or the Bretz Floods) refer to the cataclysmic floods that swept periodically across eastern Washington and down the Columbia River Gorge at the end of the last ice age. The glacial flood events have been researched since the 1920s. These glacial lake outburst floods were the result of periodic sudden ruptures of the ice dam on the Clark Fork River that created Glacial Lake Missoula. After each ice dam rupture, the waters of the lake would rush down the Clark Fork and the Columbia River, inundating much of eastern Washington and the Willamette Valley in western Oregon. After the rupture, the ice would reform, recreating Glacial Lake Missoula once again. Geologists estimate that the cycle of flooding and reformation of the lake lasted an average of 55 years and that the floods occurred several times over the 2,000-year period between 15,000 and 13,000 years ago.
Also http://en.wikipedia.org/wiki/Channeled_Scablands
Geologists simulate ancient Lake Missoula floods http://seattletimes.nwsource.com/html/localnews/2011148259_apormissoulafloods1stldwritethru.html