The Western San Juan Mountains

The Western San Juan Mountains: Their Geology, Ecology, and Human History

Managing Editor: Rob Blair
Tom Ann Casey
William H. Romme
Richard N. Ellis
Copyright Date: 1996
Pages: 406
https://www.jstor.org/stable/j.ctt46nv90
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  • Book Info
    The Western San Juan Mountains
    Book Description:

    The San Juan Skyway winds its way up, over, and through canyons, mesas, plateaus, mountains, plains, and valleys. The sheer variety of landforms makes the Skyway a veritable classroom for the amateur naturalist and historian. The most complete work published on the natural history of southwest Colorado's majestic mountain system, The Western San Juan Mountains: Their Geology, Ecology, and Human History is designed to be used while exploring the scenic 235-mile paved San Juan Skyway, which passes through Durango, Silverton, Ouray, Telluride, Dolores, and Cortez. The Western San Juan Mountains covers the physical environment, the biological communities, the human history, and points of interest represented on milepost signs along the highway. Some of the many topics covered include: how the San Juan Mountains were formed; why the landscape is so rugged and picturesque; why the vegetation changes from the lowlands to the alpine heights; energy and mineral resources of the area; why these mountains intrigued early explorers; factors that influence the unpredictable weather; and the first-known inhabitants. The contributions to this guide include Fort Lewis College geologists, biologists, archaeologists, historians, and other specialists. Together they have amassed more than one hundred years of study based not only on previous work but on their own research. This generously illustrated guidebook is aimed at all those who wish to understand this intricate mountain system in much greater detail than provided by most picture books.

    eISBN: 978-1-60732-131-6
    Subjects: Biological Sciences, Zoology, History

Table of Contents

  1. Front Matter
    (pp. i-iv)
  2. Table of Contents
    (pp. v-vi)
  3. MAPS
    (pp. vii-viii)
  4. FOREWORD
    (pp. ix-x)
    Governor Roy Romer

    Our sense of place comes from knowing where we are, where we have been, and where we are going. Knowing a place means exploring all aspects — geography, history, biology — that make it unique and special. The 235-mile highway loop known as the San Juan Skyway passes through the towns of Durango, Silverton, Ouray, Ridgway, Telluride, Dolores, Cortez, and Mancos, allowing travelers to study the many facets of southwestern Colorado. Throughout history this has been a dynamic region — the landscape has been shaped not only by time but also by those who have lived here.

    The authors explore...

  5. PREFACE
    (pp. xi-xii)
  6. ACKNOWLEDGMENTS
    (pp. xiii-xvi)
  7. PART I PHYSICAL ENVIRONMENT ALONG THE SAN JUAN SKYWAY
    • CHAPTER 1 ORIGIN OF LANDSCAPES
      (pp. 3-17)
      Rob Blair

      The San Juan Skyway, a 235-mile highway loop in southwestern Colorado, winds its way up, over, and through canyons, mesas, plateaus, mountains, plains, and valleys. The sheer variety of landforms makes the Skyway a veritable classroom for the student of geomorphology. One explanation for the large diversity of landscapes on this route is that the Skyway straddles two major physiographic provinces, the Southern Rocky Mountains and the Colorado Plateau (Fig. 1.1). Each of these regions contains a unique suite of landforms and structures.

      The Southern Rocky Mountains province dominates the Skyway loop and is represented specifically by the San Juan...

    • CHAPTER 2 PALEOTECTONIC HISTORY
      (pp. 18-37)
      Douglas C. Brew

      To unravel the geologic story of southwestern Colorado, one must understand its paleotectonic history. The field of tectonics looks at the processes that deform the earth’s crustal rocks on the global scale; paleotectonics examines such processes over the span of geologic time. The geological evolution of a region such as the San Juan Mountains might not seem to require a mechanism of global dimensions to explain it, yet the fundamental forces that have shaped this region are of that scale.

      For about 1.8 billion years southwestern Colorado has been in a position on the North American continent where its crustal...

    • CHAPTER 3 PRECAMBRIAN ROCKS
      (pp. 38-43)
      Jack A. Ellingson

      The highest peaks of the San Juan Mountains make for some impressive scenery east of U.S. Highway 550 between the Needles store and Molas Lake. The rocks of these peaks were formed during the Precambrian Era between 1.8 and 1.3 billion years ago. Precambrian rocks are also exposed in the steep walls of the spectacular Uncompahgre Canyon south of Ouray and in a small outcrop just north of Rico. Several episodes of uplift and erosion that occurred since the formation of these rocks, especially the glacial erosion during the Pleistocene, have given us this grand landscape. Mountain goats have nothing...

    • CHAPTER 4 PALEOZOIC HISTORY
      (pp. 44-53)
      John A. Campbell

      Probably the most confusing aspect of studying the geology of any area is trying to fathom the lengths of time involved. Human references to time — days, months, years, even an average life span — are simply too short. As a result, geologists have evolved a system that uses strange-sounding words for intervals of time. These words come from the geographic area where these rocks were first studied. For example, the time span known as Cambrian was first studied in Wales, the Latin name for which was Cambria. The other names on the geologic time scale have similar origins. (Please...

    • CHAPTER 5 Mesozoic and Early Cenozoic History
      (pp. 54-67)
      John A. Campbell and Douglas C. Brew

      The Mesozoic Era lasted from about 245 million to 66 million years ago. It, like the Paleozoic, is divided into shorter intervals called periods. The periods of the Mesozoic are the Triassic, Jurassic, and Cretaceous (see Stratigraphic Chart, p. 2). These periods are not of equal length: the Cretaceous is the longest, about 78 million years, and the Triassic the shortest, about 37 million years. By looking again at the Stratigraphic Chart, one can see that Mesozoic formations, like those of the Paleozoic, include unconformities, with much of the Triassic and some of parts of the Jurassic missing. These breaks...

    • CHAPTER 6 VOLCANIC ROCKS
      (pp. 68-79)
      Jack A. Ellingson

      The San Juan volcanic field is part of a much larger volcanic region that was active throughout the Southern Rocky Mountains from about 40 million to 18 million years ago (Fig. 6.1). Most eruptive centers lie within the region bounded by the Rocky Mountains on the east, the Colorado lineament on the north, and the Uncompahgre–San Luis Uplift on the south. The volcanic activity within this triangular area produced lavas and pyroclastic debris that covered all of south-central Colorado and the north-central part of New Mexico.

      The eruptions that formed this middle Tertiary volcanic field began with the formation...

    • CHAPTER 7 ORE DEPOSITS AND MINERALS
      (pp. 80-95)
      Scott Fetchenhier

      Gold! Silver! The fabulous riches of the San Juans were discovered in the last quarter of the nineteenth century, and hordes of prospectors poured into the area. Every miner had romantic visions of wealth and dreamed of enjoying the success of Leadville’s Horace Tabor or Silverton’s Stoiber brothers (of Silver Lake Mine fame). El Dorado lay over the next ridge, just waiting to be found. Mining towns and civilization sprang up with each new discovery. Some disappeared almost as quickly, products of the boom-and-bust economics of the mining and metal industries. Gold and silver were the driving forces that caused...

    • CHAPTER 8 ENERGY RESOURCES
      (pp. 96-112)
      T. L. Britt and J. M. Hornbeck

      The scenic San Juan Skyway route lies in a relatively energy-poor corridor between two major oil- and gas-producing basins, the Paradox Basin to the west and the San Juan Basin to the south. Prolific oil fields associated with Pennsylvanian-age (300 million years) algal and oolitic carbonate reservoirs of the Paradox Basin are located 25 miles west of Cortez. The eastern edge of these productive Pennsylvanian trends is defined by drilling east and north of the town of Dolores, where both Ismay and Desert Creek test wells have been completed as producers. A few miles south of Durango is the northern...

    • CHAPTER 9 WEATHER AND CLIMATE
      (pp. 113-126)
      Richard A. Keen

      It only takes a day to drive the San Juan Skyway, but on the right day you can catch a whole year’s worth of weather. It is not unusual — especially in the spring — to wake up with frost on the ground, drive through snow, hail, a thunderstorm, and 90-degree heat, and finish the day with a rainbow. The main reason for this variety is, of course, the mountains (Fig. 9.1). A loop around the Skyway takes you from the near-desert climate at Cortez, 6,000 feet (1,830 m) above sea level, to the high-country conditions on Red Mountain Pass,...

  8. PART II BIOLOGICAL COMMUNITIES ALONG THE SAN JUAN SKYWAY
    • CHAPTER 10 ECOLOGICAL PATTERNS
      (pp. 129-142)
      Albert W. Spencer and William H. Romme

      A mantle of green vegetation covers the San Juan Mountains and softens the appearance of the rugged slopes and valleys. The plant life also provides homes for myriad creatures, large and small. The study of ecology centers on patterns in distribution of plant and animal species and the reasons for these patterns. In Part 2 we examine the ecology of the San Juan Mountains. In this chapter we give an overview of the broad patterns in climate, plant life, and animals found along the Skyway and cover some fundamental concepts of ecology. Chapter 11 presents a closer look at the...

    • CHAPTER 11 BIOTIC COMMUNITIES OF THE SEMIARID FOOTHILLS AND VALLEYS
      (pp. 143-158)
      Lisa Floyd-Hanna, Albert W. Spencer and William H. Romme

      The semiarid foothills and valleys lying between 4,500 and 9,000 feet (1,400–2,750 m) occupy the largest area of the San Juan region. We will discuss the low-lying and broadest valleys, the mesas and cuestas, and the slopes and narrow valleys of the true foothills in turn, as though there were a uniform progression from one to the other. (In actuality, travelers continually pass from one to another as they drive the Skyway.) Five types of communities will be discussed: greasewood-shadscale shrub-steppe, Great Basin sagebrush shrub-steppe, piñon-juniper woodland, the mountain shrub community, and ponderosa pine–oak–Douglas fir forest. The...

    • CHAPTER 12 BIOTIC COMMUNITIES OF THE COOL MOUNTAINS
      (pp. 159-174)
      David W. Jamieson, William H. Romme and Preston Somers

      Forest vegetation is restricted to areas of relatively high precipitation and moderate temperatures. Most of the forests in the San Juan Mountains are dominated by various species of evergreen coniferous trees. Evergreens are especially well adapted to environments with short growing seasons (because of long winters, summer droughts, or both) and scarce soil nutrients. Evergreen trees need not expend a large amount of energy and nutrients in growing a full set of new leaves every year. Evergreen forests are common in the harsh climates of the northeastern and Great Lake states, in Canada, Europe, and Asia, on the infertile soils...

    • CHAPTER 13 WETLANDS, RIPARIAN HABITATS, AND RIVERS
      (pp. 175-190)
      Preston Somers and Lisa Floyd-Hanna

      Moisture is one of the premiere limiting factors for plants and animals, and where moisture is not limited one finds very distinctive communities of drought-intolerant species. Wetlands, defined as areas that remain moist through all or most of the growing season, include communities such as marshes and bogs. A special type of wetland is a riparian ecosystem (i.e., the area immediately adjacent to a flowing stream). In this chapter we discuss the characteristics and importance of the wetlands of the San Juans in general, then look more closely at the riparian vegetation that grows along the rivers and streams of...

  9. PART III HUMAN HISTORY ALONG THE SAN JUAN SKYWAY
    • CHAPTER 14 THE FORAGERS OF THE FOREST
      (pp. 193-200)
      Philip Duke

      In this chapter I will present a description of the archaeological evidence for occupation of the San Juan Skyway area by mobile hunter-gatherers (sometimes called foragers) (Fig. 14.1). Prior to the development of agriculture, hunting and gathering was the only subsistence strategy practiced in the Four Corners region. Even after the adoption of agriculture, hunting and gathering was the predominant subsistence strategy in those areas above approximately 7,000 feet (2,150 m). Hunting and gathering may have been practiced by resident forest populations, by Anasazi agriculturalists, or by both groups.

      Archaeological research in the higher reaches of the San Juan National...

    • CHAPTER 15 THE ANASAZI: PREHISTORIC FARMERS
      (pp. 201-214)
      Gary Matlock

      Two major groups of prehistoric peoples inhabited the San Juan Skyway region, the Archaic and the Anasazi. Of the two, the Anasazi are by far the better known (see Fig. 14.1, p. 192). Visitors flock from throughout the world to see the famous cliff dwellings at Mesa Verde, the silent stone cities at Chaco Canyon, and the hundreds of other prehistoric Anasazi sites in parks and monuments scattered throughout the Four Corners. Less well known, but equally important, are the thousands of Anasazi sites found on private property, Indian reservations, and lands managed by the U.S. Forest Service and Bureau...

    • CHAPTER 16 THE SPANISH
      (pp. 215-224)
      Richard N. Ellis

      Long before Anglo-Americans visited the Southwest, the area was explored and settled by the Spanish. In 1540, almost seventy years before the founding of Jamestown or the landing of the pilgrim fathers at Plymouth, Francisco Vásques de Coronado led an exploring expedition into the Southwest that took his men from western Arizona to Kansas. More than fifty years later, in 1598, Juan de Oñate undertook the colonization of New Mexico.

      New Mexico was a small and isolated frontier province at the farthest edge of the Spanish frontier, and even in the 1630s Santa Fe had a population of only some...

    • CHAPTER 17 THE UTES
      (pp. 225-233)
      Richard N. Ellis

      When the Spanish arrived in the Southwest, the people they called the Yutas, or Utes, ranged across much of present-day Colorado, northern New Mexico, and Utah. According to anthropologists, the Utes were organized into loosely defined bands, but the basic social unit was the extended family, which could most efficiently utilize the available natural resources. These small family units of perhaps ten to forty people followed a seasonal migration pattern, moving into the higher country in the spring and summer and returning to lower elevations in the autumn. They hunted deer, elk, antelope, and occasionally mountain buffalo and other animals...

    • CHAPTER 18 THE MINERS: “THEY BUILDED BETTER THAN THEY KNEW”
      (pp. 234-246)
      Duane A. Smith

      They intrigued the Spanish, lured the fifty-niners, and provided a home for several generations of eager prospectors and determined hard-rock miners. To all of them they were known as the San Juan Mountains. Some of Colorado’s highest and most rugged peaks insured a challenge for anyone who sought to wrestle their mineral resources from the granite-ribbed depths (Fig. 18.1). For over 250 years, determined men have attempted to extract the treasure.

      The Spanish came first in the eighteenth century; the Utes, who earlier had traversed these mountains for centuries, did not stop to mine. The Utes objected to the Spanish...

  10. PART IV POINTS OF INTEREST AROUND THE WESTERN SAN JUAN MOUNTAINS
    • CHAPTER 19 POINTS OF INTEREST ALONG THE SAN JUAN SKYWAY
      (pp. 249-347)
      Rob Blair

      This road guide is meant for the visitor who wishes to delve into the geology, ecology, archaeology, and history of the San Juan Skyway region. The guide is designed to be flexible so that a traveler can enter the highway at any point and circle the loop in either direction. The points of interest are identified on topographic maps (Fig. 19.1, Maps 19.1 through 19.20, and Maps 21.1 through 21.3) by open circles, with corresponding numbers referenced in this chapter. Areas of interest are designated with black-filled circles. Many of the points of interest are referenced to the green milepost...

    • CHAPTER 20 POINTS OF INTEREST ALONG THE DURANGO-TO-SILVERTON NARROW-GAUGE RAILROAD
      (pp. 348-350)
      Rob Blair

      The mournful whistle of the narrow-gauge train echoes between the canyon walls as much today as it did in 1882, when service began between Durango and Silverton. The train ride is only 46 miles, but it takes more than three hours to complete. From Durango to Rockwood follow the log given for the highway (Points of Interest 7 through 25).

      The rail bed rises from 6,500 feet (2,000 m) at Durango to just over 9,300 feet (2,850 m) at Silverton. Because the line follows the Animas River, it is mostly confined to a riparian environment. Thus, narrowleaf cottonwood, box elder,...

    • CHAPTER 21 POINTS OF INTEREST ALONG THE ALPINE LOOP
      (pp. 351-364)
      Barbara Byron

      The Alpine Loop provides easy access into the lofty San Juan Mountains and offers the inquisitive eye an “unequaled field for the observation of the processes of nature.” There are no milepost signs along the Alpine Loop; therefore, points of interest are located by odometer readings beginning in Silverton. The traveler is guided north up the Animas River toward Animas Forks and over Cinnamon Pass to Lake City. Odometer readings begin again at 0.0 at Lake City, where the route turns up Henson Creek, over Engineer Pass, and on toward Ouray.

      The Alpine Loop follows the original wagon route pioneered...

  11. GLOSSARY
    (pp. 365-372)
  12. CONTRIBUTORS
    (pp. 373-376)
  13. INDEX
    (pp. 377-406)