Mount Rainier Part 16

A striking example of an ice body nourished wholly by the snows falling on the lower slope of Mount Rainier is the Paradise Glacier.

In no wise connected with the summit neves, it makes its start at an elevation of less than 9,000 feet. Situated on the spreading slope between the diverging canyons of the Nisqually on the west and of the Cowlitz on the northeast, it const.i.tutes a typical "interglacier," as intermediate ice bodies of this kind are termed.

Its appearance is that of a gently undulating ice field, creva.s.sed only toward its lower edge and remarkably clean throughout. No debris-shedding cliffs rise anywhere along its borders, and this fact, no doubt, largely explains its freedom from morainal acc.u.mulations.

The absence of cliffs also implies a lack of protecting shade.

Practically the entire expanse of the glacier lies exposed to the full glare of the sun. As a consequence its losses by melting are very heavy, and a single hot summer may visibly diminish the glacier's bulk. Nevertheless it seems to hold its own as well as any other glacier on Mount Rainier, and this ability to recuperate finds its explanation in the exceeding abundance of fresh snows that replenish it every winter.

The Paradise Glacier, however, is not the product wholly of direct precipitation from the clouds. Much of its ma.s.s is supplied by the wind, and acc.u.mulates in the lee of the high ridge to the west, over which the route to Camp Muir and Gibraltar Rock is laid. The westerly gales keep this ridge almost bare of snow, permitting only a few drifts to lodge in sheltered depressions. But east of the ridge there are great eddies in which the snow forms long, smooth slopes that descend several hundred feet to the main body of the glacier. These slopes are particularly inviting to tourists for the delightful "glissades" which they afford. Sitting down on the hard snow at the head of such a slope, one may indulge in an exhilarating glide of amazing swiftness, landing at last safely on the level snows beneath.

The generally smooth and united surface of the Paradise Glacier, it may be added, contributes not a little to its attractiveness as a field for alpine sports. On it one may roam at will without apprehension of lurking peril; indeed one can journey across its entire width, from Paradise Park to the Cowlitz Rocks, without encountering a single dangerous fissure. This general absence of creva.s.ses is accounted for largely by the evenness of the glacier's bed and by its hollow shape, owing to which the snows on all sides press inward and compact the ma.s.s in the center. Only toward its frontal margin, where the glacier plunges over an abrupt rock step, as well as in the hump of that part known as Stevens Glacier, is the ice rent by long creva.s.ses and broken into narrow blades. Here it may be wise for the inexperienced not to venture without a competent guide, for the footing is apt to be treacherous, and jumping over creva.s.ses or crossing them by frail snow bridges are feats never accomplished without risk.

In the early part of summer the Paradise Glacier has the appearance of a vast, unbroken snow field, blazing, immaculate, in the sun. But later, as the fresh snows melt away from its surface, grayish patches of old crystalline ice develop in places, more especially toward the glacier's lower margin. Day by day these patches expand until, by the end of August, most of the lower ice field has been stripped of its brilliant mantle. Its countenance, once bright and serene, now a.s.sumes a grim expression and becomes crisscrossed by a thousand seams, like the visage of an aged man.

Over this roughened surface trickle countless tiny rills which, uniting, form swift rivulets and torrents, indeed veritable river systems on a miniature scale that testify with eloquence to the rapidity with which the sun consumes the snow. Strangely capricious in course are these streamlets, for, while in the main gravitating with the glacier's slope, they are ever likely to be caught and deflected by the numerous seams in the ice. These seams, it should be explained, are lines of former creva.s.ses that have healed again under pressure in the course of the glacier's slow descent. As a rule they inclose a small amount of dirt, and owing to its presence are particularly vulnerable to erosion. Along them the streamlets rapidly intrench themselves--perhaps by virtue of their warmth, what little there is of it, as much as by actual abrasion--and hollow out channels of a freakish sort, here straight and ca.n.a.l-like, there making sharp zigzag turns; again broadening into profound, canoe-shaped pools, or emptying into deeper trenches by little sparkling cataracts, or pa.s.sing under tiny bridges and tunnels--a veritable toy land carved in ice.

But unfortunately these pretty features are ephemeral, many of them changing from day to day; for, evenings, as the lowering sun withdraws its heat, the melting gradually comes to a halt, and the little streams cease to flow. The soft babbling and gurgling and the often exquisitely melodious tinkle of dripping water in hidden glacial wells are hushed, and the silent frost proceeds to choke up pa.s.sages and channels, so that next day's waters have to seek new avenues.

In the region where the new creva.s.ses open the surface drainage comes abruptly to an end. Here gaping chutes of deepest azure entrap the torrents and the waters rush with musical thunder to the interior of the glacier and finally down to its bed.

At its lower border the Paradise Glacier splits into several lobes.

The westernmost sends forth the Paradise River, which, turning southwestward, plunges over the Sluiskin Fall (named for the Klickitat Indian who guided Van Trump and Hazard Stevens to the mountain in 1870, when they made the first successful ascent) and runs the length of Paradise Valley. The middle lobe has become known as Stevens Glacier (named for Hazard Stevens) and ends in Stevens Creek, a stream which almost immediately drops over a precipice of some 600 feet--the Fairy Falls--and winds southeastward through rugged Stevens Canyon.

The easternmost lobes, known collectively as Williwakas Glacier, send forth two little cascades, which, uniting, form Williwakas Creek. This stream is a tributary of the Cowlitz River, as is Stevens Creek.

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 part.i.tion a thousand feet in height. 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 neves 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 part.i.tion, 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 pa.s.sing, 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, 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 debris.

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 debris 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 quant.i.ties of debris, much of it in the form of cobbles and bowlders, 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 debris held by the pa.s.sing 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, pa.s.ses 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 quant.i.ty 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 bowlders 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 bowlder beds.

High above the Ingraham Glacier towers that sharp, residual ma.s.s of lava strata known as Little Tahoma (11,117 feet), the highest outstanding eminence on the flank of Mount Rainier. It forms a gigantic "wedge" that divides the Ingraham from the Emmons Glacier to the north. So extensive is this wedge that it carries on its back several large ice fields and interglaciers, some of which, lying far from the beaten path of the tourist, are as yet unnamed. Separating them from each other are various attenuated, pinnacled crests, all of them subordinate to a main backbone that runs eastward some 6 miles and terminates in the Cowlitz Chimneys (7,607 feet), a group of tall rock towers that dominate the landscape on the east side of Mount Rainier.

Most of the ice fields, naturally, lie on the shady north slope of the main backbone; in fact, a series of them extends as far east as the Cowlitz Chimneys. One of the lesser crests, however, that running southeastward to the upland region known as Cowlitz Park, also gives protection to an ice body of some magnitude, the Ohanapecosh Glacier.

Considerably broader than it is long in the direction of its flow, this glacier lies on a high shelf a mile and a half across, whence it cascades down into the head of a walled-in canyon. Formerly, no doubt, it more than filled this canyon, but now it sends down only a shrunken lobe. The stream that issues from it, the Ohanapecosh River, is really the main p.r.o.ng and head of the Cowlitz River.

The largest and most elevated of the ice fields east of Little Tahoma is known for its peculiar shape as Fryingpan Glacier. It covers fully 3 square miles of ground and const.i.tutes the most extensive and most beautiful interglacier on Mount Rainier. It originates in the hollow east side of Little Tahoma itself and descends rapidly northward, overlooking the great Emmons Glacier and finally reaching down almost to its level. It is not a long time since the two ice bodies were confluent.

The eastern portion of the Fryingpan Glacier drains northeastward and sends forth several cascading torrents which, uniting with others coming from the lesser ice fields to the east, form the Fryingpan River, a brisk stream that joins White River several miles farther north.

Below the Fryingpan Glacier there lies a region of charming flower-dotted meadows named Summerland, a most attractive spot for camping.

Cloaking almost the entire east side of Mount Rainier is the Emmons Glacier, the most extensive ice stream on the peak (named after Samuel F. Emmons, the geologist and mountaineer who was the second to conquer the peak in 1870). About 5-1/2 miles long and 1-3/4 miles wide in its upper half, it covers almost 8 square miles of territory. It makes a continuous descent from the summit to the base, the rim of the old crater having almost completely broken down under its heavy neve cascades. But two small remnants of the rim still protrude through the ice and divide it into three cascades. From each of these dark rock islands trails a long medial moraine that extends in an ever-broadening band down to the foot of the glacier.

Conspicuous lateral moraines accompany the ice stream on each side.

There are several parallel ridges of this sort, disposed in successive tiers above each other on the valley sides. Most impressively do they attest the extent of the Emmons Glacier's recent shrinking. The youngest moraine, fresh looking as if deposited only yesterday, lies but 50 feet above the glacier's surface and a scant 100 feet distant from its edge; the older ridges, subdued in outline, and already tinged with verdure, lie several hundred feet higher on the slope.

The Emmons Glacier, like the Nisqually and the Cowlitz, becomes densely littered with morainal debris at its lower end, maintaining, however, for a considerable distance a central lane of clear ice. The stream which it sends forth, White River, is the largest of all the ice-fed streams radiating from the peak. It flows northward and then turns in a northwesterly direction, emptying finally in Puget Sound at the city of Seattle.

On the northeast side of the mountain, descending from the same high neves as the Emmons Glacier, is the Winthrop Glacier. Not until halfway down, at an elevation of about 10,000 feet, does it detach itself as a separate ice stream. The division takes place at the apex of that great triangular inters.p.a.ce so aptly named "the Wedge." Upon its sharp cliff edge, Steamboat Prow, the descending neves part, it has been said, like swift-flowing waters upon the dividing bow of a s.h.i.+p at anchor. The simile is an excellent one; even the long foam crest, rising along the s.h.i.+p's side, is represented by a wave of ice.

Undoubtedly the Wedge formerly headed much higher up on the mountain's flank. Perhaps it extended upward in the form of a long, attenuated "cleaver." It is easy to see how the ice ma.s.ses impinging upon it have reduced it to successively lower levels. They are still unrelentingly at work. It is on the back of the Wedge, it may be added here, that is situated that small ice body which Maj. Ingraham named the "Interglacier." That name has since been applied in a generic sense to all similar ice bodies lying on the backs of "wedges."

Of greatest interest on the Winthrop Glacier are the ice cascades and domes. Evidently the glacier's bed is a very uneven one, giving rise to falls and pools, such as one observes in a turbulent trout stream.

The cascades explain themselves readily enough, but the domes require a word of interpretation. They are underlain by rounded bosses of especially resistant rock. Over these the ice is lifted, much as is the water of a swift mountain torrent over submerged bowlders.

Immediately above each obstruction the ice appears compact and free from creva.s.ses, but as it reaches the top and begins to pour over it breaks, and a network of intersecting cracks divides it into erect, angular blocks and fantastic obelisks. Below each dome there is, as a rule, a deep hollow partly inclosed by trailing ice ridges, a.n.a.logous to the whirling eddy that occurs normally below a bowlder in a brook.

Thus does a glacier simulate a stream of water even in its minor details.

The domes of the Winthrop Glacier measure 50 to 60 feet in height. A sample of the kind of obstruction that produces them appears, as if specially provided to satisfy human curiosity, near the terminus of the glacier. There one may see, close to the west wall of the troughlike bed, a projecting rock ma.s.s, rounded and smoothly polished, over which the glacier rode but a short time ago.

Another feature of interest sometimes met with on the Winthrop Glacier, and for that matter also on the other ice streams of Mount Rainier, are the "glacier tables." These consist of slabs of rock mounted each on a pedestal of snow and producing the effect of huge toadstools. The slabs are always of large size, while the pedestals vary from a few inches to several feet in height.

The origin of the rocks may be traced to cliffs of incoherent volcanic materials that disintegrate under the frequent alternations of frost and thaw and send down periodic rock avalanches, the larger fragments of which bound out far upon the glacier's surface.

The snow immediately under these large fragments is effectually protected from the sun and does not melt, while the surrounding snow, being unprotected, is constantly wasting away, often at the rate of several inches per day. Thus in time each rock is left poised on a column of its own conserving. There is, however, a limit to the height which such a column can attain, for as soon as it begins to exceed a certain height the protecting shadow of the capping stone no longer reaches down to the base of the pedestal and the slanting rays of the sun soon undermine it. More commonly, however, the south side of the column becomes softened both by heat transmitted from the sun-warmed south edge of the stone, as well as by heat reflected from the surrounding glacier surface, and as a consequence the table begins to tilt. On very hot days, in fact, the inclination of the table keeps pace with the progress of the sun, much after the manner of a sun-loving flower, the slant being to the southeast in the forenoon and to the southwest in the afternoon. As the snow pillar increases in height it becomes more and more exposed and the tilting is accentuated, until at last the rock slides down.

In its new position the slab at once begins to generate a new pedestal, from which in due time it again slides down, and so the process may be repeated several times in the course of a single summer, the rock s.h.i.+fting its location by successive slips an appreciable distance across the glacier in a southerly direction.

As has been stated, the slabs on glacier tables are always of large size. This is not a fortuitous circ.u.mstance; rocks under a certain size, and especially fragments of little thickness, cannot produce pedestals; in fact, far from conserving the snow under them, they accelerate its melting and sink below the surface. This is especially true of dark-colored rocks. Objects of dark color, as is well known to physicists, have a faculty for absorbing heat, whereas light-colored objects, especially white ones, reflect it best. Dark-colored fragments of rock lying on a glacier, accordingly, warm rapidly at their upper surface and, if thin, forthwith transmit their heat to the snow under them, causing it to melt much faster than the surrounding clean snow, which, because of its very whiteness, reflects a large percentage of the heat it receives from the sun. As a consequence each small rock fragment and even each separate dust particle on a glacier melts out a tiny well of its own, as a rule not vertically downward but at a slight inclination in the direction of the noonday sun. And thus, in some localities, one may behold the apparently incongruous spectacle of large and heavy rocks supported on snow pillars alongside of little fragments that have sunk into the ice.

There is also a limit to the depth which the little wells may attain; as they deepen, the rock fragment at the bottom receives the sun heat each day for a progressively shorter period, until at last it receives so little that its rate of sinking becomes less than that of the melting glacier surface. Nevertheless it will be clear that the presence of scattered rock debris on a glacier must greatly augment the rate of melting, as it fairly honeycombs the ice and increases the number of melting surfaces. Wherever the debris is dense, on the other hand, and acc.u.mulates on the glacier in a heavy layer, its effect becomes a protective one and surface melting is r.e.t.a.r.ded instead of accelerated. The dirt-covered lower ends of the glaciers of Mount Rainier are thus to be regarded as in a measure preserved by the debris that cloaks them; their life is greatly prolonged by the unsightly garment.

In many ways the most interesting of all the ice streams on Mount Rainier is the Carbon Glacier, the great ice river on the north side, which flows between those two charming natural gardens, Moraine Park and Spray Park. The third glacier in point of length, it heads, curiously, not on the summit, but in a profound, walled-in amphitheater, inset low into the mountain's flank. This amphitheater is what is technically known as a glacial cirque, a horseshoe-shaped basin elaborated by the ice from a deep gash that existed originally in the volcano's side. It has the distinction of being the largest of all the ice-sculptured cirques on Mount Rainier, and one of the grandest in the world. It measures more than a mile and a half in diameter, while its head wall towers a sheer 3,600 feet. So well proportioned is the great hollow, however, and so simple are its outlines that the eye finds difficulty in correctly estimating the dimensions. Not until an avalanche breaks from the 300-foot neve cliff above and hurls itself over the precipice with cras.h.i.+ng thunder, does one begin to realize the depth of the colossal recess. The falling snow ma.s.s is several seconds in descending, and though weighing hundreds of tons, seemingly floats down with the leisureliness of a feather.

These avalanches were once believed to be the authors of the cirque.

They were thought to have worn back the head wall little by little, even as a waterfall causes the cliff under it to recede. But the real manner in which glacial cirques evolve is better understood to-day. It is now known that cirques are produced primarily by the eroding action of the ice ma.s.ses embedded in them. Slowly creeping forward, these ice ma.s.ses, shod as they are with debris derived from the encircling cliffs, scour and scoop out their hollow sites, and enlarge and deepen them by degrees. Seconding this work is the rock-splitting action of water freezing in the interstices of the rock walls. This process is particularly effective in the great cleft at the glacier's head, between ice and cliff. This abyss is periodically filled with fresh snows, which freeze to the rock; then, as the glacier moves away, it tears or plucks out the frost-split fragments from the wall. Thus the latter is continually being undercut. The overhanging portions fall down, as decomposition lessens their cohesion, and so the entire cliff recedes.

A glacier, accordingly, may be said, literally, to gnaw headward into the mountain. But, as it does so, it also attacks the cliffs that flank it, and as a consequence, the depression in which it lies tends to widen and to become semicircular in plan. In its greatest perfection a glacial cirque is horseshoe-shaped in outline. The Carbon Glacier's amphitheater, it will be noticed, consists really of two twin cirques, separated by an angular b.u.t.tress. But this projection, which is the remnant of a formerly long spur dividing the original cavity, is fast being eliminated by the undermining process, so that in time the head wall will describe a smooth, uninterrupted horseshoe curve.

In its headward growth the Carbon Glacier, as one may readily observe on the map, has encroached considerably upon the summit platform of the mountain, the ma.s.sive northwest portion of the crater rim of which Liberty Cap is the highest point. In so doing it has made great inroads upon the neve fields that send down the avalanches, and has reduced this source of supply. On the other hand, by deploying laterally, the glacier has succeeded in capturing part of the neves formerly tributary to the ice fields to the west, and has made good some of the losses due to its headward cutting. But, after all, these are events of relatively slight importance in the glacier's career; for like the lower ice fields of the Nisqually, and like most glaciers on the lower slopes of the mountain, the Carbon Glacier is not wholly dependent upon the summit neves for its supply of ice. The avalanches, imposing though they are, contribute but a minor portion of its total bulk. Most of its ma.s.s is derived directly from the low hanging snow clouds, or is blown into the cirque by eddying winds. How abundantly capable these agents are to create large ice bodies at low alt.i.tudes is convincingly demonstrated by the extensive neve fields immediately west of the Carbon Glacier, for which the name Russell Glacier has recently been proposed. It is to be noted, however, that these ice fields lie spread out on shelves fairly exposed to sun and wind. How much better adapted for the acc.u.mulation of snow is the Carbon Glacier's amphitheater! Not only does it const.i.tute an admirably designed catchment basin for wind-blown snow, but an effective conserver of the neves collecting in it. Opening to the north only, its encircling cliffs thoroughly s.h.i.+eld the contained ice ma.s.s from the sun. By its very form, moreover, it tends to prolong the glacier's life, for the latter lies compactly in the hollow with a relatively small surface exposed to melting. The cirque, therefore, is at once the product of the glacier and its generator and conserver.

Of the lower course of the Carbon Glacier little need here be said, as it does not differ materially from the lower courses of the glaciers already described. It may be mentioned, however, that toward its terminus the glacier makes a steep descent and develops a series of parallel medial moraines and that it reaches down to an elevation of 3,365 feet, almost 600 feet lower than any other ice stream on Mount Rainier. A beautiful cave usually forms at the point of exit of the Carbon River.

West of the profound canyon of the Carbon River, there rises a craggy range which the Indians have named the Mother Mountains. From its narrow backbone one looks down on either side into broadly open, semicircular valley heads. Some drain northward to the Carbon River, some southward to the Mowich River. Encircling them run attenuated rock part.i.tions, surmounted by low, angular peaks; while cutting across their stairwise descending floors are precipitous steps of rock, a hundred feet in height. On the treads lie scattered shallow lakelets, strung together by little silvery brooks trickling in capricious courses.

Most impressive is the basin that lies immediately under the west end of the range. Smoothly rounded like a bowl, it holds in its center an almost circular lake of vivid emerald hue--that mysterious body of water known as Crater Lake. Let it be said at once that this appellation is an unfortunate misnomer. The basin is not of volcanic origin. It lies in lava and other volcanic rocks, to be sure, but these are merely spreading layers of the cone of Mount Rainier. Ice is the agent responsible for the carving of the hollow. It was once the cradle of a glacier, and that ice ma.s.s, gnawing headward and deploying even as the Carbon Glacier does to-day, enlarged its site into a horseshoe basin, a typical glacial cirque. The lake in the center is a strictly normal feature; many glacial cirques possess such bowls, scooped out by the eroding ice ma.s.ses from the weaker portions of the rock floor; only it is seldom that such features acquire the symmetry of form exhibited by Crater Lake. The lakelets observed in the neighboring valley heads--all of which are abandoned cirques--are of similar origin.