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This publication is one of a series of handbooks explaining the natural history of scenic and scientific areas in the National Park System administered by the National Park Service, U.S. Department of the Interior. It is printed by the Government Printing Office and may be purchased from the Superintendent of Documents, Washington, D.C., 20401

Price 35 cents

ROCKY MOUNTAIN NATIONAL PARK ? COLORADO

NATIONAL PARK SERVICE Natural History Handbook Series

No. 1. Olympic National Park No. 2. Badlands National Monument No. 3. Rocky Mountain National Park No. 4. Saguaro National Monument No. 5. Great Smokey Mountains National Park

Administration

Rocky Mountain National Park, established on January 26, 1915, and containing about 410 square miles, is administered by the National Park Service, U.S. Department of the Interior.

The National Park System, of which this park is a unit, is dedicated to conserving the scenic, scientific, and historic heritage of the United States for the benefit and enjoyment of its people.

A superintendent is in immediate charge of Rocky Mountain National Park, with headquarters in Estes Park village on the east side of the park. Address communications to the Superintendent, Rocky Mountain National Park, Box 1086, Estes Park, Colo.

America's Natural Resources

Created in 1849, the Department of the Interior--America's Department of Natural Resources--is concerned with the management, conservation, and development of the Nation's water, wildlife, mineral, forest, and park and recreational resources. It also has major responsibilities for Indian and territorial affairs.

As the Nation's principal conservation agency, the Department works to assure that nonrenewable resources are developed and used wisely, that park and recreational resources are conserved, and that renewable resources make their full contribution to the progress, prosperity, and security of the United States--now and in the future.

Contents

Park rangers are often asked, "What are the main attractions of Rocky Mountain National Park?" It is hard to answer this question, for the appeal of the park, somewhat like that of a symphony, lies in the varied yet repeated experiences or melodies which may be found within its framework. The raw beauty of the rugged mountains contrasts with the calm loveliness of wildflower gardens growing nearby. Some visitors enjoy the solitude, while others appreciate the opportunity to meet people with like interests and to hike with organized groups on some of the 200 miles of trails. Many derive pleasure from quietly studying the fascinating world of nature preserved in the park. Some vigorously battle the steep slopes of the mountains; others relax in camp, soothed by the sound of the wind in the trees. Each person enjoys the park in his own way. There are regulations, but no regimentation, no compulsory activities, no "musts." The park was established for all to use, but not to abuse.

Rocky Mountain National Park comprises about 400 square miles of the Front Range. The altitude of the park is high, with cool summers the inevitable result. There are more than 65 named peaks exceeding 10,000 feet. The Continental Divide, separating slopes draining to the Pacific Ocean from those draining to the Gulf of Mexico, runs through the park.

To those who study it, the park reveals stories of great natural dramas of earth forces that made its deep gorges and lofty peaks, and of once-mighty glaciers that carved its remote lakes. Its forests and wildflowers tell a story of struggle and adjustment to environments that differ with altitude and exposure. Its native populations--deer, elk, bear, beaver, birds and the myriad lesser creatures of the wild--can be seen in their natural habitats. Its streams attract the hopeful fisherman; its unmodified natural compositions enthrall the artist; its cool, green setting appeals to all summer travelers.

Enos Mills, "father" of Rocky Mountain National Park, wrote about 40 years ago:

A National Park is a fountain of life.... Without parks and outdoor life all that is best in civilization will be smothered. To save ourselves--to enable us to live at our best and happiest, parks are necessary. Within National Parks is room--glorious room--room in which to find ourselves, in which to think and hope, to dream and plan, to rest, and resolve.

His words are even more significant to our generation than they were to his. This booklet is an attempt to provide a concise summary of some of the park's important natural values and to arouse your appetite for further pursuit of the enjoyment they offer. The basic experience in this National Park, as in most, is to capture some of the inspiration and spiritual qualities of the landscape which Enos Mills felt so keenly.

THE MOUNTAINS ARE MADE

The geological story of Rocky Mountain National Park is a long one. Most of its details are lost in the passage of hundreds of millions of years. Some of the story has been put together by scientists from bits of evidence scattered here and there. The evidence strongly indicates a certain chain of events, but no eyewitnesses are available to confirm the deductions. Few of these events can be proved to everyone's satisfaction; we can but pass on to you some determinations that geologists have made.

Most of the rocks which you see in the park are crystalline and very ancient. The gneiss and schist were, in part, once sediments formed in seas, perhaps a billion years ago, under conditions about which there is little knowledge or general agreement. These sediments were buried beneath thousands of feet of other sediments, cemented and hardened into layers of sedimentary rock and later squeezed, crushed, and elevated by slow, ceaselessly working earth forces that produced mountains even in that ancient time. During this period the sedimentary rocks were changed to harder metamorphic rocks, probably because of deep burial under tremendous pressure and considerable heat. Masses of molten rock welled up into these earlier deposits and hardened under the earth's surface. This later intrusive material is now exposed granite in many parts of Rocky Mountain National Park.

These ancient mountains were gradually worn away by wind, rain, and other agents of erosion, which must have attacked the surface of the earth as vigorously then as now. With the passage of millions of years, these mountains were reduced to a lowland. Another sea gradually lapped over the land where mountains had been, and once again sediments were dropped in its bottom. This new invasion of the ocean affected the park region during many millions of years in which the dinosaurs dominated the earth.

In response to little-understood rhythms of the earth's crust, which have lifted mountains ever so slowly at great intervals all over the world, the seas drained away as the crust rose again, and the rising land once more became subject to the ceaseless attack of erosion. This uplift--which began about 60 million years ago--originated the system of mountain ranges and basins that today give Colorado its spectacular scenery and much of its climate. This great period of mountain-making is called the Laramide Revolution, from its early recognition in the Laramie Basin region of Wyoming.

The Front Range, of which this park preserves a choice sample, was buckled in the fashion of a great long wrinkle in a carpet. This "roll" of rock was about 200 miles long and some 40 miles across. In its earlier stages it was covered by the arched-up sediments, but, as time passed and erosion continued, the inner core of earlier crystalline rocks was exposed once again. Today, all traces of the former thick mantle of sedimentary beds are gone from the park. They are still present beneath the plains to the east and the basins to the west, and the cut-off ends of some of them now lie exposed in a tilted position against both east and west flanks of the mountains. The sandstones of some of the hogback ridges crossed by the approach roads from Lyons and Loveland are a part of this once continuous overburden.

Uplift continued intermittently during many millions of years. In the western section of the park, volcanic eruptions took place. Specimen Mountain is the remnant of a volcano; some of its flows are seen today as the cliffs behind Iceberg Lake, on Trail Ridge Road. Great sheets of lava and other volcanic rocks piled in layers now make up much of the Never Summer Range. Eventually, these rocks, too, will be stripped away by the relentless work of erosion; this will require millions of years.

An unusual feature of the landscape here is the rolling, sometimes flattened character of many mountain summits. Trail Ridge Road crosses several miles of one of these summits--a gently rolling upland above 11,000 feet. These mountaintops appear to be all that is left of an old land surface that once may have been continuous far eastward over the area occupied today by the Great Plains. Such surfaces, of which the mountains in the park show many good remnants, are called peneplains. Their presence atop the mountains is a part of the evidence suggesting that the range had been worn down by erosion to a fairly flat upland a few million years ago. Then renewed uplifting occurred, and streams draining the highland gradually cut canyons two or three thousand feet into the elevated surface.

THE WORK OF GLACIERS

These canyons were filled by glaciers at intervals during the million years of the ice age. This period saw the formation of vast ice fields over much of northern North America. The causes of the ice age are complex, but its effects on our landscape are marked and convincing.

Every large high-altitude canyon in what is now Rocky Mountain National Park became filled with snow, much of which, under pressure, turned to ice. The glaciers thus formed, moving under their own great weight--slowly, but with tremendous power--broadened, deepened, and straightened the twists and turns of the original river-cut valleys, and, bit by bit, scooped out bowls, or cirques, at the glacier sources. These glaciers quarried and removed untold millions of tons of rocks from the upper reaches. Many of the cliffs and lakes of the park are the results of excavating done by the mountain glaciers.

These glaciers were entirely local; they did not extend down to the plains in this region. At what is now an altitude of about 8,200 feet--just below present-day Moraine Park, Horseshoe Park, Wild Basin, and a few miles below Grand Lake in the Colorado River valley--the glacier fronts melted as fast as the ice advanced. It was there that most of the rock debris plucked from higher up was dropped. Piles of rock are scattered over most of the meadowlands of this general altitude. These rock deposits are called moraines--ridges and heaps, or scattered masses, of unsorted rock debris dumped where they settled from the melting ice. Classic examples of moraines may be seen in Moraine Park, named for these special features. You can learn more about them at the Moraine Park Visitor Center.

When climatic changes caused the glaciers to melt back faster than they advanced, the moraines, like modern dams, formed lakes behind them whenever stream drainage from the shrinking glaciers was checked. Several such lakes, now silted in and changed to green meadows, occupied lower regions in the park. There are good examples of these lakes in Horseshoe Park and Moraine Park.

The glaciers invaded the park valleys several times during the ice age. Usually, two distinguishable ages of moraines can be seen; the older and more extensive one is made up of well-weathered, "rotten" boulders and finer material, while the newer ones are scarcely altered at all. It is thought that the last great glaciers retreated only some 12,000 years ago. Indians lived on the plains at that time!

It is by no means certain that the glacier age is entirely a thing of the past. Five small glaciers, or "glacierets," of geologically recent origin--Taylor, Andrews, Tyndall, Rowe, and Sprague--exist today in the park. They are much smaller than the earlier glaciers; but they are ice masses, and they are moving ; so they are glaciers by definition. They are accessible only by arduous foot travel, but the first three are visible from heavily traveled roads and trails of the park.

The story of the geological events, as we have seen, is long. The landscape of today, we now realize, is transient. It is the contemporary product of processes that have been working day and night throughout geologic time. These processes will certainly go on and on, and inevitably will continue to change the landscape. Each year sees some little modification here and there. These small changes are not linked in our thinking with the vast sweep of geologic time, probably because our own lives are so very short. With some reflection we seem to catch glimpses of eternity as we examine the ancient gray cliffs and mighty peaks of Rocky Mountain National Park.

THE MOUNTAINS ARE MANTLED WITH PLANTS

Having seen that the present mountains are the result of past events, we should not be surprised to learn that the plant cover of the park is also dependent on what has occurred before. We are inclined to think of a plant community, such as a forest, as a permanent fixture; but it is a dynamic, never-stagnant population of individual living things, and in some ways resembles a community of people.

Just as human populations ebb and flow through periods of great numerical growth and dominance, followed by decline and engulfment by invading peoples, so do vegetation types go through periods of dominance and decline. When certain conditions of climate and soil prevail, those kinds of plants best adapted to such conditions will dominate the scene. As conditions change, the flora will change.

In Rocky Mountain National Park, we assume that toward the end of the ice age most of the high altitude landscape was either ice-covered or barren, like our present-day rockpiles above treeline. As the ice melted and disappeared, the bare rocks of the canyons were exposed, and lakes occupied what are now the meadows. The climate was changing, though, and the rather sparse arctic-type plantlife was superseded by another vegetation complex, except on the very tops of the mountains.

The ice-age vegetation was presumably connected with that of the regions bordering the Arctic Ocean. The present tundra of the high country in the park is an island of arctic-type vegetation, surrounded on all sides by plant communities of lower latitudes. Will it be engulfed some day and replaced by surrounding plant types? If the climate continues to moderate, the answer may be "Yes."

Most of the original sparse arctic flora has already disappeared. The bare rocks were first invaded by lichens--those plant pioneers still to be seen on rocks in the park. In the thin soil formed by their life processes, other primitive plants became established. As the climate moderated and soils formed where bare rocks formerly existed, a new vegetation complex replaced the old.

We suppose that all sorts of plants got started on this new land, but only those species which happened to be adapted for the particular conditions of their time would last long enough to become well established and to produce ample seeds for future generations. This selective elimination of plants which were not adjusted to the changing conditions results in the dominance of certain well-adjusted species. In this way, according to scientists, a climax vegetation develops for a particular situation. As long as the climate remains about the same, the climax vegetation remains relatively stable.

Although it has been thousands of years since these plant communities first started on the glaciated bedrock, the struggle for dominance among the plants still goes on. Conditions are not yet completely static and probably never will be. The meadows, the forests, and the barrens of today may be quite different in a distant tomorrow.

PLANT COMMUNITIES

Below 9,000 Feet

In the lower slopes of the park, below approximately 9,000 feet altitude, usually described as the Montane zone, the climate is relatively warm and dry. This type of climate has encouraged a fairly consistent pattern of vegetation that may be considered climax. The forests in this zone are open. The trees are likely to be scattered in characteristically parklike stands and are made up mostly of ponderosa pine. On cool north slopes the stands are thicker, with Douglas-fir sprinkled in or even dominant. With the ponderosa pine on drier sites is juniper , and above 8,000 feet thick stands of lodgepole pine are sometimes admixed. Along the streams are the distinctive and graceful Colorado blue spruce, associated with willows, birch, and alder. Aspen groves and, in lower altitudes, cottonwoods appear here and there. Many types of shrubs, some characteristic of the foothills, grow in the Montane zone.

The most characteristic forest tree of the lower part of this zone is PONDEROSA PINE. It has dull-green needles from 3 to 6 inches long--longer than those of other pines in the park--which are usually in bundles of three. Although the bark on young trees is black, the mature trees have a yellow-brown bark in characteristically rectangular plates. The cones are about 3 inches long, with prickles on the tips of the cone scales. Capable of growing in warm, dry environments, it is an evergreen of south-facing slopes and is widespread as a forest tree in the southwestern United States. On the cooler, north-facing slopes, DOUGLAS-FIR mingles with the ponderosa pine. Douglas-fir is easily identified by its needles, which grow singly along the branch instead of in sheaths. The needles are flat, blunt, and about 1 inch long; and they have a narrow stalk at the base that pulls off with the needle. This distinguishes it from the blue spruce often found in the same vicinity. The bark is smooth and gray on young trees, but rough, brownish, and deeply furrowed on older trees. The cones are about 2 inches long, made up of broad scales each with a projecting 3-pronged bract. Here, Douglas-fir seldom attains the great size for which it is noted in the Pacific Northwest.

Another conifer growing in this zone, usually along streams or in such other wet locations, is BLUE SPRUCE, one of the most admired evergreens of the West. Its needles produce a bloom, or powder, which gives the tree a distinctive bluish or silver aspect, especially noticeable in midsummer. The cones are from 3 to 5 inches long, tan-colored, with many scales, which have narrow tips but no prickles.

In the upper parts of the Montane zone grow dense forests of LODGEPOLE PINE, so named because the Indians used it for tepee poles. It is characterized by tall, slender, straight trunks, with most of the foliage near the top. Its trunk is usually much smaller than the other conifers of the region--seldom exceeding 20 inches. The bark is much thinner than that of the ponderosa pine; gray scales on the bark of young trees become brown with age. The cones are about 2 inches long and are borne in clusters of two or three, tightly attached to the branch. Cones often remain on the tree for years, the seeds retaining their vitality. After a light forest fire, the undamaged cones will open, releasing the seeds. This is nature's way of reseeding a fire-swept area and explains the extremely dense stands of lodgepole pine which, for example, you will see near Many Parks Curve.

ROCKY MOUNTAIN JUNIPER can be seen on dry hills and rocky canyon walls in the park. Its scalelike leaves are small and flattened against the innumerable branches. It has no cones, but bears little, bluish berries, which require two seasons to ripen. Usually this juniper grows in a squat and sprawling manner.

The most common deciduous tree in the park is QUAKING ASPEN. It is immediately recognized by its smooth, white bark and small, green leaves that tremble with the slightest breeze, because of the curious flattening of the petiole, or leaf stalk, at right angles to the leaf blade. Aspen grows to considerable size in beautiful groves of tall trees, where the moisture and shelter are sufficient, but is more often seen in scrubby thickets on rocky, drier slopes. In September the leaves turn to a golden color, giving early autumn travelers a matchless visual experience. NARROW-LEAF COTTONWOOD grows along streams in the lower altitudes of the park. Many willows also occupy streambank environments, the most common being SCOULER WILLOW with characteristic willow leaves and large oval catkins, which are quite conspicuous in May and early June.

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