Immediately adjoining the Paradise Glacier on the northeast, and not separated from it by any definite barrier, lies the Cowlitz Glacier, one of the stateliest ice streams of Mount Rainier. It flows in a southeasterly direction, and burrows its nose deeply into the forest-covered hills at the mountain's foot. Its upper course consists of two parallel-flowing ice streams, intrenched in profound troughs, which they have enlarged laterally until now only a narrow, ragged crest of rock remains between them, resembling a partition a thousand feet in height. (Fig. 10.) At the upper end of this crest stands Gibraltar Rock.
At the point of confluence of the two branches there begins a long medial moraine that stretches like a black tape the whole length of the lower course. To judge by its position midway on the glacier's back, the two tributaries must be very nearly equal in strength, yet, when traced to their sources, they are found to originate in widely different ways. The north branch, named Ingraham Glacier (after Maj. E. S. Ingraham, one of Rainier's foremost pioneers), comes from the névés on the summit; while the south branch heads in a pocket immediately under Gibraltar. No snow comes to it from the summit; hence we can not escape the conclusion that it receives through direct precipitation and through wind drifting about as much snow as its sister branch receives from the summit regions. Like the glacier troughs below, the pocket appears to have widened laterally under the influence of the ice, and is now separated from the Nisqually ice fields to the west by only a narrow rock partition, the Cowlitz Cleaver, as it is locally called. Up this narrow crest the route to Gibraltar Rock ascends. The name "cleaver," it may be said in passing, is most apt for the designation of a narrow rock crest of this sort, and well deserves to be more generally used in the place of awkward foreign terms, such as arrete and grat.
Both branches of the Cowlitz Glacier cascade steeply immediately above their confluence (fig. 11), but the lower glacier has a gentle gradient and a fairly uneventful course. Like the lower Nisqually, it is bordered by long morainal ridges, and toward its end acquires broad marginal dirt bands. For nearly a mile these continue, leaving a gradually narrowing lane of clear ice between them. Then they coalesce and the whole ice body becomes strewn with rock débris.
The Cowlitz Glacier, including its north branch, the Ingraham Glacier, measures slightly over 6 miles in length. Throughout that distance the ice stream lies sunk in a steep-walled canyon of its own carving. Imposing cliffs of columnar basalt, ribbed as if draped in corduroy, overlook its lower course. Slender waterfalls glide down their precipitous fronts, like silver threads, guided by the basalt flutings.
From the end of the glacier issues the Muddy Fork of the Cowlitz River, which, joining the Ohanapecosh, forms the Cowlitz River proper, one of the largest streams of the Cascade Range. For nearly a hundred miles the Cowlitz River follows a southwesterly course, finally emptying in the Columbia River a short distance below Portland, Oregon.
The name Muddy Fork is a most apt one, for the stream leaves the glacier heavily charged with débris and mud, and while it gradually clears itself as it proceeds over its gravelly bed, it is still turbid when it reaches the Ohanapecosh. That stream is relatively clear, for it heads in a glacier of small extent and little eroding power, and consequently begins its career with but a moderate load; furthermore it receives on its long circuitous course a number of tributaries from the Cascade Range, all of them containing clear water.
The name Muddy, however, might with equal appropriateness be given to every one of the streams flowing from the ice fields of Mount Rainier. So easily disintegrated are the volcanic materials of which that peak is composed, that the glaciers are enabled to erode with great rapidity, even in their present shrunken state. They consequently deliver to the streams vast quantities of débris, much of it in the form of cobbles and boulders, but much of it also in the form of "rock flour."
A considerable proportion of a glacier's erosional work is performed by abrasion or grinding, its bed being scoured and grooved by the rock blocks and smaller débris held by the passing ice. As a result glacier streams ordinarily carry much finely comminuted ??? rock, or rock flour, and this, because of its fineness, remains long in suspension and imparts to the water a distinctive color. In regions of light-colored rocks the glacier streams have a characteristic milky hue, which, as it fades out, passes over into a delicate turquoise tint. But the lavas of Mount Rainier produce for the most part dark-hued flour, and as a consequence the rivers coming from that peak are dyed a somber chocolate brown.
A word may not be out of place here about the sharp daily fluctuations of the ice-fed rivers of the Mount Rainier National Park, especially in view of the difficulties these streams present to crossing. There are fully a score of turbulent rivers radiating from the peak, and as a consequence one can not journey far through the park without being obliged to cross one of them. On all the permanent trails substantial bridges obviate the difficulty, but in the less developed portions of the park, fording is still the only method available. It is well to bear in mind that these rivers, being nourished by melting snow, differ greatly in habit from streams in countries where glaciers are absent. Generally speaking, they are highest in summer and lowest in winter; also, since their flow is intimately dependent upon the quantity of snow being melted at a given time, it follows that in summer when the sun reaches its greatest power they swell daily to a prodigious volume, reaching a maximum in the afternoon, while during the night and early morning hours they again ebb to a relatively moderate size. In the forenoon of a warm summer day one may watch them grow hourly in volume and in violence, until toward the middle of the day they become raging torrents of liquid mud in which heavy cobbles and even boulders may be heard booming as they roll before the current. It would be nothing short of folly to attempt to ford under these conditions, whether on horseback or on foot. In the evening, however, and still better, in the early morning, one may cross with safety; the streams then have the appearance of mere mountain brooks wandering harmlessly over broad boulder beds.
Last Updated: 07-May-2007