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Ancient Ice

by Chester Marler

At the head of the Entiat River is a series of striking meadows, punctuated by groves of subalpine fir and Engelmann spruce, set beneath an arc of towering summits. This parkland is called the Entiat Meadows, and was a favored destination for sheep grazing during the early decades of the 20th century. Although the sheep have long been absent, the area is rich with wildlife, its alternating meadows and forest strips providing habitat for healthy populations of mule deer and cinnamon colored black bears. This pattern of large meadows, divided by dense stands of conifers, continues for six miles in the upper Entiat Valley. It ends with the Entiat cirque, formed by the imposing walls of Mt. Maude, Seven Fingered Jack and Mt. Fernow, all over 9,000 feet tall and 500 feet higher than major peaks to the west along the Cascade Crest. The Entiat Glaciers, remnants of the Little Ice Age, barely cling to the steep and fractured walls of the three peaks.

 

Camping near the head of the valley, where patches of meadow blend into bouldery stretches of moraines, is an experience one will always remember—its images defining this part of the Cascades. The setting is stunning to be sure, but equally fascinating is what one can see of geologically recent changes to the landscape brought by the rhythm of alternating patterns of cold and warm—of ice encroaching on the valley, and at a later time, plant communities re-colonizing the land as the ice receded.

 

Long before the Little Ice Age, during the last glacial maximum of the Pleistocene Epoch (18,000 years or so ago), the Entiat Glacier extended far down the valley, shaping and sculpting much of the valley topography. The river of ice, thousands of feet thick, gouged a deep U-shaped valley, leaving the side valleys truncated at the height of the ice mass. These hanging valleys have more gradual gradients at their mid-point, but then drop steeply where the edge of the old valley glacier cut its trough. The transition in steepness is noticed immediately when climbing from the bottom of the Entiat Valley into Larch Lakes Basin or Cow Creek Meadows, hanging valleys nearly 2,000 feet above the valley floor. Only the graded trail switchbacks alleviate the need to ascend the natural steepness of the terrain. In contrast, the Entiat Valley trail follows the bottom of a U-shaped valley, carved by ice from its head to the lower valley. Only at its headwaters, in the cirque formed by three towering summits, is the gradual gradient broken by steep walls.

 

By 8,000 to 10,000 years ago, the large valley glaciers had retreated, exposing the effects of thousands of years of alternating ice advance and recession. Long periods of glacial action had sculpted the summits, steep cirques and rocky ridges of the range. Valley bottom soils, where tall conifers now grow, were deposited by silt-laden streams and rivers flowing from the melting ice as warming trends reduced its total mass. Nearly all the landscape we see today, whether rock or vegetation, was either shaped by ice age events or has developed since the time of major ice retreat. All the forested areas, the high mountain parklands, the total pattern of plant communities we travel through today, are of recent origin, established after the last great ice event. Using almost any time scale to measure natural change, the landscape we see today is fresh. Only because of the brevity of our personal scale of time—our own experiences and lifetimes—are we sometimes drawn to view the mountain world as static or nearly changeless—except for the obvious rhythm of seasonal change. In reality, changes to the mountain environment are never ending, and will continue. The only issue is how much of that change will be human caused.

 

The Little Ice Age, a 14th-to-19th century phenomenon, returned advancing ice to the Cascades, but on a much less grand scale. Only the highest cirques were affected, partially filling with ice again. The Entiat Glaciers we see today are remnants of that period. The retreat of the glaciers of the Little Ice Age in the 19th century exposed a series of concentric terminal moraines at the head of the valley, easily recognized when seen from the side-slopes of the upper valley. The highest elevation moraines are geologically fresh, being only about 150 years old. Their rocky contours are steep and sometimes unstable, at times making travel slow and tiresome. Because the piles of rubble are so young, they are mostly devoid of vegetation, with pioneering species just beginning to gain a hold. Moraines downstream are slightly older and are now becoming covered with areas of grasses, sedges, partridge foot and in places, alpine larch. Much older moraines, near the lower end of the Entiat Meadows, have been transformed by vegetation and subsequent erosion, making them more difficult to detect amidst other features of the landscape. The moraines mark the temporary halting points of the retreating mass of ice, where the melting of ice is balanced by ice flowing from the glacier’s upper end. The terminus of the glacier remains stationary, while debris carried by the glacier is dropped off and accumulated as the ice melts.

 

At the end of hot, dry summers, when the previous winter’s snow is completely gone, old ice and snow are clearly exposed across the Entiat cirque. All that remains is a darker ice body, some of it from many decades before. Yet, there are years when the winter snowpack is deep enough, and the spring and summer cool enough, that the oldest ice is mostly covered, and the “young” snow left over from the previous winter gives the ice masses a white appearance. If a series of years like this occurs, then the glaciers seem fresher, and for a time, tend to stabilize in size. But in the majority of years from the mid-1970s until recently, the glaciers of the Eastern Slope of the Cascades have struggled to maintain their size. More often then not, I see ancient ice in the late summer, the darker colored, hard vestiges of a slightly cooler climate. I wish for it to be otherwise, because the white brilliance and sound of a growing glacier are dramatic, but we exist in a world consisting of changes both slow and fast, few of which correspond to individual human wishes. But one can imagine what it would be like to see the Cascades during a period of glacial advance: active glaciers growing down-slope, meeting and then enveloping meadows and forests, crushing conifers hundreds of years old, re-enacting a scene that has occurred many times over thousands of years.

 The essay above above about the little ice age is excerpted from Chester Marler's book titled, East of the Divide.  The next excerpt will discuss how avalanches have also shaped the Cascadisan landscape.