during my first boyish exploring trip in the rocky mountains i was impressed with the stupendous changes which the upper slope of these mountains had undergone. in places were immense embankments and wild deltas of débris that plainly had come from elsewhere. in other places the rough edges of the ca?ons and ridges had been trimmed and polished; their cliffs and projections were gone and their surfaces had been swept clean of all loose material. later, i tried vainly to account for some ca?on walls being trimmed and polished at the bottom while their upper parts were jagged. in most ca?ons the height of the polishings above the bottom was equal on both walls, with the upper edge of the polish even or level for the entire length of the ca?on. in one ca?on, in both floor and walls, were deep lateral scratches in the rocks.[pg 248]
one day i found some polished boulders perched like driftwood on the top of a polished rock dome; they were porphyry, while the dome was flawless granite. they plainly had come from somewhere else. how they managed to be where they were was too much for me. mountain floods were terrible but not wild enough in their fiercest rushes to do this. upon a mountainside across a gorge about two miles distant, and a thousand feet above the perched boulders on the dome, i found a porphyry outcrop; but this situation only added to my confusion. i did not then know of the glacial period, or the actions of glaciers. it was a delightful revelation when john muir told me of these wonders.
much of the earth's surface, together with most mountain-ranges, have gone through a glacial period or periods. there is extensive and varied evidence that the greater portion of the earth has been carved and extensively changed by the ice king. substantial works, blurred and broken records, and impressive ruins in wide array over the earth show long and active possession by the ice king, as eloquently as the[pg 249] monumental ruins in the seven hills tell of their intense association with man.
both the northern and the southern hemispheres have had their heavy, slow-going floods of ice that appear to have swept from the polar world far toward the equator. during the great glacial period, which may have lasted for ages, a mountainous flood of ice overspread america from the north and extended far down the mississippi valley. this ice may have been a mile or more in depth. it utterly changed the topography and made a new earth. lakes were filled and new ones made. new landscapes were formed: mountains were rubbed down to plains, morainal hills were built upon plains, and streams were moved bodily.
it is probable that during the last ice age the location and course of both the ohio and the missouri rivers were changed. originally the missouri flowed east and north, probably emptying into a lake that had possession of the lake superior territory. the ice king deliberately shoved this river hundreds of miles toward the south. the ohio probably had a sim[pg 250]ilar experience. these rivers appear to mark the "farthest south" of the ice; their position probably was determined by the ice. had a line been traced on the map along the ragged edge and front of the glacier at its maximum extension, this line would almost answer for the present position of the missouri and ohio rivers.
the hallett glacier the hallett glacier
the most suggestive and revealing words concerning glaciers that i have ever read are these of john muir in "the mountains of california": "when we bear in mind that all the sierra forests are young, growing upon moraine soil recently deposited, and that the flank of the range itself, with all its landscapes, is new-born, recently sculptured, and brought to light of day from beneath the ice mantle of the glacial winter, then a thousand lawless mysteries disappear and broad harmonies take their places."
"a glacier," says judge junius henderson, in the best definition that i have heard, "is a body of ice originating in an area where the annual accumulation of snow exceeds the dissipation, and moving downward and outward to an area where dissipation exceeds accumulation."
[pg 251]
a glacier may move forward only a few feet in a year or it may move several feet in a day. it may be only a few hundred feet in length, or, as during the ice age, have an area of thousands of square miles. the arapahoe glacier moves slowly, as do all small glaciers and some large ones. one year's measured movement was 27.7 feet near the centre and 11.15 near the edge. this, too, is about the average for one year, and also an approximate movement for most small mountain glaciers. the centre of the glacier, meeting less resistance than the edges, commonly flows much more rapidly. the enormous alaskan glaciers have a much more rapid flow, many moving forward five or more feet a day.
a glacier is the greatest of eroding agents. it wears away the surface over which it flows. it grinds mountains to dust, transports soil and boulders, scoops out lake-basins, gives flowing lines to landscapes. beyond comprehension we are indebted to them for scenery and soil.
glaciers, or ice rivers, make vast changes. those in the rocky mountains overthrew cliffs,[pg 252] pinnacles, and rocky headlands. these in part were crushed and in part they became embedded in the front, bottom, and sides of the ice. this rock-set front tore into the sides and bottom of its channel—after it had made a channel!—with a terrible, rasping, crushing, and grinding effect, forced irresistibly forward by a pressure of untold millions of tons. glaciers, large and small, the world over, have like characteristics and influences. to know one glacier will enable one to enjoy glaciers everywhere and to appreciate the stupendous influence they have had upon the surface of the earth.
they have planed down the surface and even reduced mountain-ridges to turtle outlines. in places the nose of the glacier was thrust with such enormous pressure against a mountainside that the ice was forced up the slope which it flowed across and then descended on the opposite side. sustained by constant and measureless pressure, years of fearful and incessant application of this weighty, flowing, planing, ploughing sandpaper wore the mountain down. in time, too, the small ragged-edged, v-shaped[pg 253] ravines became widened, deepened, and extended into enormous u-shaped glaciated gorges.
glaciers have gouged or scooped many basins in the solid rock. these commonly are made at the bottom of a deep slope where the descending ice bore heavily on the lever or against a reverse incline. the size of the basin thus made is determined by the size, width, and weight of the glacier and by other factors. in the rocky mountains these excavations vary in size from a few acres to a few thousand. they became lake-basins on the disappearance of the ice.
more than a thousand lakes of glacial origin dot the upper portions of the rocky mountains of colorado. most of these are above the altitude of nine thousand feet, and the largest, grand lake, is three miles in length. landslides and silt have filled many of the old glacier lake basins, and these, overgrown with grass and sedge, are called glacier meadows.
vast was the quantity of material picked up and transported by these glaciers. mountains were moved piecemeal, and ground to boulders, pebbles, and rock-flour in the moving. in addi[pg 254]tion to the material which the glacier gathered up and excavated, it also carried the wreckage brought down by landslides and the eroded matter poured upon it by streams from the heights. most of the material which falls upon the top of the upper end of the glacier ultimately works its way to the bottom, where, with the other gathered material, it is pressed against the bottom and sides and used as a cutting or grinding tool until worn to a powder or pebbles.
train-loads of débris often accumulate upon the top of the glacier. on the lower course this often is a hundred feet or more above the surface, and as the glacier descends and shrivels, enormous quantities of this rocky débris fall off the sides and, in places, form enormous embankments; these often closely parallel long stretches of the glacier like river levees.
the large remainder of the material is carried to the end of the glacier, where the melting ice unloads and releases it. this accumulation, which corresponds to the delta of a river, is the terminal moraine. for years the bulk of the ice[pg 255] may melt away at about the same place; this accumulates an enormous amount of débris; an advance of the ice may plough through this and repile it, or the retreat of the ice or a changed direction of its flow may pile the débris elsewhere and over wide areas. many of these terminal moraines are an array of broken embankments, small basin-like holes and smooth, level spaces. the débris of these moraines embraces rock-flour, gravel, pebbles, a few angular rock-masses, and enormous quantities of many-sized boulders,—rocks rounded by the grind of the glacial mill.
strange freight, of unknown age, these creeping ice rivers bring down. one season the frozen carcass of a mountain sheep was taken from the ice at the end of the arapahoe glacier. if this sheep fell into a crevasse at the upper end of the glacier, its carcass probably had been in the ice for more than a century. human victims, too, have been strangely handled by glaciers. it appears that in 1820 dr. hamil and a party of climbers were struck by a snowslide on the slope of mont blanc. one escaped with his life,[pg 256] while the others were swept down into a crevasse and buried so deeply in the snow and ice that their bodies could not be recovered. scientists said that at the rate the glacier was moving it would give up its dead after forty years. far down the mountain forty-one years afterward, the ice gave up its victims. a writer has founded on this incident an interesting story, in which the bodies are recovered in an excellent state of preservation, and an old woman with sunken cheeks and gray hair clasps the youthful body of her lover of long ago, the guide.
where morainal débris covers thousands of acres, it is probable that valuable mineral veins were in some cases covered, prospecting prevented, and mineral wealth lost; but on the other hand, the erosion done by the glacier, often cutting down several hundred feet, has in many cases uncovered leads which otherwise probably would have been left buried beyond search. then, too, millions of dollars of placer gold have been washed from moraines.
in addition to the work of making and giving[pg 257] the mountains flowing lines of beauty, the glaciers added inconceivably to the richness of the earth's resources by creating vast estates of soil. it is probable that glaciers have supplied one half of the productive areas of the earth with soil; the mills of the glaciers have ground as much rock-flour—soil—for the earth as wind, frost, heat, and rain,—all the weathering forces. this flour and other coarser glacial grindings were quickly changed by the chemistry of nature into plant-food,—the staff of life for forests and flowers.
glaciers have not only ground the soil but in many places have carried this and spread it out hundreds of miles from the place where the original raw rocks were obtained. wind and water have done an enormous amount of work sorting out the soil in moraines and, leaving the boulders behind, this soil was scattered and sifted far and wide to feed the hungry plant-life.
at last the glacial winter ended, and each year more snow melted and evaporated than fell. snow-line retreated up the slopes and finally became broken, even in the heights. to-[pg 258]day, in the rockies, there are only a dozen or so small glaciers, mere fragments of the once great ice cap which originally covered deeply all the higher places and slopes, and extended unbroken for hundreds of miles, pierced strangely with a few sharp peaks.
the small remaining glaciers in the rocky mountains lie in sheltered basins or cirques in the summits and mostly above the altitude of thirteen thousand feet. these are built and supplied by the winds which carry and sweep snow to them from off thousands of acres of treeless, barren summits. the present climate of these mountains is very different from what it was ages ago. then for a time the annual snowfall was extremely heavy. each year the sun and the wind removed only a part of the snow which fell during the year. this icy remainder was added to the left-over of preceding years until the accumulation was of vast depth and weight.
on the summit slopes this snow appears to have been from a few hundred to a few thousand feet deep. softened from the saturation of melting and compressed from its own weight, it be[pg 259]came a stratum of ice. this overlay the summit of the main ranges, and was pierced by only a few of the higher, sharper peaks which were sufficiently steep to be stripped of snow by snowslides and the wind.
the weight of this superimposed icy stratum was immense; it was greater than the bottom layers could support. ice is plastic—rubbery—if sufficient pressure or weight be applied. under the enormous pressure the bottom layers started to crawl or flow from beneath like squeezed dough. this forced mass moved outward and downward in the direction of the least resistance,—down the slope. thus a glacier is conceived and born.
numbers of these glaciers—immense serpents and tongues of ice—extended down the slopes, in places miles beyond the line of perpetual snow. some of these were miles in length, a thousand or more feet wide, and hundreds of feet deep, and they forced and crushed their way irresistibly. it is probable they had a sustained, continuous flow for centuries.
a glacier is one of the natural wonders of the[pg 260] world and well might every one pay a visit to one of these great earth-sculpturers. the time to visit a glacier is during late summer, when the snows of the preceding winter are most completely removed from the surface. with the snows removed, the beauty of the ice and its almost stratified make-up are revealed. the snow, too, conceals the yawning bergschlunds and the dangerous, splendid crevasses. a visit to one of these ponderous, patient, and effective monsters is not without danger; concealed crevasses, or thinly covered icy caverns, or recently deposited and insecurely placed boulders on the moraines are potent dangers that require vigilance to avoid. however, the careful explorer will find one of these places far safer than the city's chaotic and crowded street.
a crevasse a crevasse
for the study of old glacier records few places can equal the estes park district in colorado. the arapahoe, on arapahoe peak, colorado, is an excellent glacier to visit. it is characteristic and is easy of access. it is close to civilization,—within a few miles of a railroad,—is comprehensively situated, and is amid some of the grandest [pg 261] scenery in the rocky mountains. it has been mapped and studied, and its rate of movement and many other things concerning it are accurately known. it is the abstract and brief chronicle of the ice age, a key to all the glacier ways and secrets.
in the arapahoe glacier one may see the cirque in which the snow is deposited or drifted by the wind; and the bergschlund-yawn—crack of separation—made by glacier ice where it moves away from the névé or snowy ice above. in walking over the ice in summer one may see or descend into the crevasses. these deep, wide cracks, miniature ca?ons, are caused by the ice flowing over inequalities in the surface. at the end of this glacier one may see the terminal moraine,—a raw, muddy pile of powdered, crushed, and rounded rocks. farther along down the slope one may see the lakes that were made, the rocks that were polished, and the lateral moraine deposited by the glacier in its bigger days,—times when the ice king almost conquered the earth.
in the rocky mountains the soil and mo[pg 262]rainal débris were transported only a few miles, while the wisconsin and iowa glaciers brought thousands of acres of rich surfacing, now on the productive farms of ohio, illinois, and iowa, from places hundreds of miles to the north in canada. in the rocky mountains most of the forests are growing in soil or moraines that were ground and distributed by glaciers. thus the work of the glaciers has made the earth and the mountains far more useful in addition to giving them gentler influences,—charming lakes and flowing landscape lines. it is wonderful that the mighty worker and earth-shaper, the ice king, should have used snowflakes for edge-tools, millstones, and crushing stamps!
to know the story of the ice king—to be able to understand and restore the conditions that made lakes and headlands, moraines and fertile fields—will add mightily to the enjoyment of a visit to the rocky mountains, the alps, the coasts and mountains of norway and new england, alaska's unrivaled glacier realm, or the extraordinary ice sculpturing in the yosemite national park.[pg 263]
edward orton, jr., formerly state geologist of ohio, who spent weeks toiling over and mapping the mills moraine on the east slope of long's peak, gave a glimpse of what one may feel and enjoy from nature investigation in his closing remarks concerning this experience. he said, "if one adds to the physical pleasures of mountaineering, the intellectual delight of looking with the seeing eye, of explaining, interpreting, and understanding the gigantic forces which have wrought these wonders; if by these studies one's vision may be extended past the sublime beauties of the present down through the dim ages of the past until each carved and bastioned peak tells a romance above words; if by communion with this greatness, one's soul is uplifted and attuned into fuller accord with the great cosmic forces of which we are the higher manifestation, then mountaineering becomes not a pastime but an inspiration."