Chapter

Quaternary International, 2017

This paper argues that the Rocky Mountains played a significantly more important role in the process of the peopling of the New World than archaeologists have traditionally recognized. Although First Americans did not reach the Rockies before they set foot in any other New World regiondthey could not have, regardless of their point of entrydby Clovis time, evidence suggests that Clovis people knew the Rocky Mountain landscape intimately. Archaeologists should have long anticipated this, given the many resources the Rocky Mountains offer that adjacent, albeit archaeologically better-known regions such as the Plains and some parts of the Far West do not; at least not as ubiquitously. These include plentiful water in the form of streams, lakes, snowpack, and glaciers; high-quality sources of obsidian, chert, quartzite and other knappable stone; and a vertically oriented landscape that maximizes floral and faunal diversity within comparatively condensed space. Two other non-economic characteristics likely contributed significantly to the appeal of the Rocky Mountains to some First Americans: the power and sanctity nearly all humans attribute to mountains, and the seemingly little-recognized fact that northeast Asian Upper Paleolithic people who populated the New World during the terminal Pleistocene occupied mountainous landscapes for some 45,000 years prior to their departure. For many First Americans, mountainsdnot the flat, windswept tundra of Si-berian stereotypesdhad always been home. Evidence for the familiarity of Clovis groups with the Rocky Mountain landscapes comes principally from three Clovis caches: Anzick, Fenn, and Mahaffy. All three caches are located in the Rockies, collectively contain artifacts made from ten of the highest-quality stone raw materials available in the Southern, Central and Northern Rockies, and at least one of the caches accompanies the burial of a young child who appears to have been interred intentionally on a prominent and likely sacred landform in a mountain valley. Bringing the paper's argument full circle, that same child's genetic profile shows a direct link to that of another youngster buried thousands of years earlier at the Late Glacial Maximum Mal'ta site in the mountainous Trans-Baikal region of Siberia.

Encyclopedia of Archaeology (ed. by D.M. Pearsall), 2007

The text content for your contribution is in final form when you receive proofs. Read proofs for accuracy and clarity, as well as for typographical errors, but please DO NOT REWRITE.

AMBIO: A Journal of the Human Environment, 2000

Professional Paper

This Professional Paper is the first multitemporal assessment of late-20th-century land change in the conterminous United States across all regions and all land-use and land-cover sectors. The work is the culmination of nearly 10 years of research and development by the U.S. Geological Survey, with support from the U.S. Environmental Protection Agency and the National Aeronautics and Space Administration, as well as university collaborators. It represents the most complete and comprehensive analysis of the rates, types, distribution, and drivers of recent changes in land use and land cover. The study bridges the gap between coarse-scale continental and global assessments and fine-scale local and regional case studies. Land-change studies attempt to explain the "what, where, when, how, and why" of changes to the vegetation and to the use of the land. Land-change research is aimed specifically at measuring where change is occurring (and where it is not occurring); which land-use and land-cover classes are changing (and what they are changing to); how much land is changing (and how fast); and what drivers are responsible for the measured changes. The goal is not only to understand the scope of change but also to provide the information base necessary to evaluate, predict, and manage the consequences of change. Like many key issues in climate change and ecosystem functioning, land use and land cover are both drivers and indicators of environmental quality. The National Research Council has identified the understanding of land-use dynamics as one of the grand challenges for environmental research-no other global-change parameter is so tightly intertwined with issues of past, present, and future land-use practices, weather patterns, soil and carbon dynamics, ecosystem health and diversity, economic development and policy, technology issues, human population size and distribution, and overall human health. People and their use of the land are interrelated in complex ways, and the effects of land-use and land-cover change can have a huge impact on their quality of life, on the goods and services that they can expect from the land, and on the hazards that they may face. Despite these profound consequences, the Intergovernmental Panel on Climate Change's Third Assessment Report has cited the lack of scientific understanding about the timing, magnitude, and direction of response of ecological, social, and economic systems to the combined effects of climate change and land-use and land-cover change as a key uncertainty in determining societal vulnerabilities and predicting both regional and global impacts of climate change. Prior to this study, only sectorally specific or spatially limited assessments and inventories had been conducted to categorize land change in the United States. These efforts often included only certain land-use and land-cover classes or ownership categories, or they were conducted over short time intervals only, and integrating these various assessments into a comprehensive and consistent national synthesis of land change was not possible. The research presented in this Professional Paper has been specifically designed to provide the first comprehensive measurement of land-cover change in the conterminous United States. Relying on Landsat satellite imagery-the longest continuous and consistent dataset of synoptic Earth observations-the authors characterize changes across 11 primary land-use and land-cover classes spanning four time periods between 1973 and 2000. For each of these time periods and classes, estimates of change are developed for each of 84 distinct ecological regions-or ecoregions-across the conterminous United States. The results provide useful, if not essential, information for understanding climate change, biodiversity, resource management and planning, resource security, and disaster planning. A significant conclusion is that no single profile of land-use and land-cover change exists. Numerous different, and often complex, interactions between an ecoregion's socioeconomic drivers and its biological and physical characteristics have produced widespread regional and temporal variability in the rates, types, and total extent of land change. Among the scientific findings presented are estimates of overall forest decline in response to increased rates of disturbance, urbanization, and agricultural intensification. This research provides a critical ecoregional to national perspective of land change in the conterminous United States. With the completion of the 1973-2000 assessment, this study lays a foundation for understanding the Nation's land-change dynamics and makes possible a new era for analyzing the consequences of land change, as well as for modeling future land changes.

Climatic Change, 1994

The zenith of Anasazi Pueblo Indian occupation in the northern Colorado Plateau region of the southwestern U.S.A. coincides with the Little Climatic Optimum or Medieval Warm Period (A.D. 900–1300), and its demise coincides with the commencement of the Little Ice Age. Indexes of winter (jet-stream derived) and summer (monsoon derived) precipitation and growing season length were developed for the La Plata Mountains region of southwestern Colorado. The results show that during the height of the Little Climatic Optimum (A.D. 1000–1100) the region was characterized by a relatively long growing season and by a potential dry farming zone or elevational belt (currently located between 2,000 m and 2,300 m elevation) that was twice as wide as present and could support Anasazi upland dry farming down to at least 1,600 m, an elevation that is quite impossible to dry farm today because of insufficient soil moisture. This expanded dry-farm belt is attributable to a more vigorous circulation regime characterized by both greater winter and summer precipitation than that of today. Between A.D. 1100 and 1300 the potential dry-farm belt narrowed and finally disappeared with the onset of a period of markedly colder and drier conditions than currently exist. Finally, when the Little Ice Age terminated in the mid A.D. 1800s and warmer, wetter conditions returned to the region, another group of farmers (modern Anglos) were able to dry farm the area.

2014

Mesic to somewhat xeric sites over a broad range of topographic conditions including ravines, valley flats, sheltered low ridges, lower to mid-slopes, and steep, exposed slopes. Soils are usually acidic, tending toward sandy and gravelly soils. Species diversity tends to be low. Vegetation Description The characteristic species are eastern white pine (Pinus strobus), sugar maple (Acer saccharum), paper, gray, black, sweet, and yellow birch (Betula papyrifera, B. cordifolia, B. nigra, B. lenta, B. alleghaniensis), beech (Fagus grandifolia), northern red oak (Quercus rubra), white oak (Q. alba). American chestnut (Castanea) would have been a co-dominant before its near-extirpation. Other common associates include eastern hemlock (Tsuga canadensis), striped maple (A. pensylvanicum), red maple (A. rubrum), mountain maple (A. spicatum), white ash (Fraxinus americana), black cherry (Prunus serotina), basswood (Tilia americana), and American elm (Ulmus americana). Occasional associates mig...

Arctic, Antarctic, and Alpine Research, 2017

A comprehensive mid-20th century inventory of glaciers and perennial snowfields (G&PS) was compiled for the American West, west of the 100° meridian. The inventory was derived from U.S. Geological Survey 1:24,000 topographic maps based on aerial photographs acquired during 35 years, 1955-1990, of which the first 20 years or more was a cool period with little glacier change. The mapped features were filtered for those greater than 0.01 km 2. Results show that 5036 G&PS (672 km 2 , 14 km 3) populate eight states, of which about 1276 (554 km 2 , 12 km 3) are glaciers. Uncertainty is estimated at ±9% for area and ±20% for volume. Two populations of G&PS were identified based on air temperature and precipitation. The larger is found in a maritime climate of the Pacific Northwest, characterized by warm winter air temperatures and high winter precipitation (~2100 mm). The other population is continental in climate, characterized by cold winter air temperatures, relatively low winter precipitation (~880 mm), and located at higher elevations elsewhere. The G&PS in the Pacific Northwest, especially in the Olympic Mountains, are particularly vulnerable to warming winter air temperatures that will change the phase of winter precipitation from snow to rain, further accelerating glacier shrinkage in the future. Comparison with a recent inventory suggests that the total G&PS area in the American West may have decreased by as much as 39% since the mid-20th century.

Continental rifts:evolution, structure, tectonics

Geosphere

The Rocky Mountain Front (RMF) trends north-south near long 105°W for ~1500 km from near the U.S.-Mexico border to southern Wyoming. This long, straight, persistent structural boundary originated between 1.4 and 1.1 Ga in the Mesoproterozoic. It cuts the 1.4 Ga Granite-Rhyolite Province and was intruded by the shallow-level alkaline granitic batholith of Pikes Peak (1.09 Ga) in central Colorado. The RMF began as a boundary between thick cratonic lithosphere to the east (modern coordinates) and an orogenic plateau to the west and remains so today. It was reactivated during the 1.1 to 0.6 Ga breakup of the supercontinent Rodinia and during deformation associated with formation of both the Ancestral and Laramide Rocky Mountains. Its persistence as a cratonic boundary is also indicated by emplacement of alkalic igneous rocks, goldtelluride deposits, and other features that point to thick lithosphere, low heat fl ow, and episodic mantle magmatism from 1.1 Ga to the Neogene. Both rollback of the Farallon fl at slab ca. 37 Ma and initiation of the Rio Grande Rift shortly thereafter began near the RMF. Geomorphic expression of the RMF was enhanced during the late Miocene to Holocene (ca. 6-0 Ma) by tectonic uplift and increased monsoonal precipitation that caused differential erosion along the mountain front, exhuming an imposing 0.5-1.2 km escarpment, bordered by hogbacks of Phanero zoic strata and incised by major river canyons. Here we investigate four right-stepping defl ections of the RMF that developed during the Laramide orogeny and may reveal timing and structural style. The Sangre de Cristo Range to Wet Mountains and Wet Mountains to Front Range steps are related to reactivation of the eroded stumps of Ancestral Rocky Mountain uplifts. In northern Colorado, the Colorado Mineral Belt (CMB) ends at the RMF; no signifi cant northeast-trending faults cross the Front Range-Denver Basin boundary. However, several features changed from south to north across the CMB. (1) The axis of the Denver Basin was defl ected ~60 km to the northeast. (2) The trend of the RMF changed from north-northwest to north. (3) Structural style of the Front Range-Denver Basin margin changed from northeast-vergent thrusts to northeast-dipping, high-angle reverse faults. (4) Early Laramide uplift north of the CMB was accompanied by southeastward slumping and décollement faulting of upper Cretaceous sedimentary units. (5) The Boulder-Weld coal fi eld developed within the zone of décollement faulting. (6) The huge Wattenberg gas field formed over a paleogeothermal anomaly. (7) Apatite fi ssion track (AFT) cooling ages in the Front Range north of the CMB are almost all associated with Laramide deformation (ca. 80-40 Ma), whereas south of the CMB, AFT ages in the Front Range and Wet Mountains vary widely (ca. 449-30 Ma). Proterozoic rocks still retain pre-Laramide AFT ages in a zone as much 1200 m thick south of the CMB, revealing comparatively modest uplift and erosion. A fourth step is a ~250 km defl ection of the RMF from the Laramie Range to the Black Hills of South Dakota along the southeastern boundary of the Wyoming Archean province. Laramide synorogenic sedimentation occurred mainly in Paleocene and early Eocene time on both sides of the Front Range in Colorado, but the timing and style of basin-margin thrusting differed markedly. Moderate-to high-angle thrusts and reverse faults characterized the east side beginning in the Maastrichtian (ca. 68 Ma). On the west side, low-angle thrusts overrode the Middle Park and South Park basins by 10-15 km beginning in the latest Paleocene-early Eocene. This later contraction correlates temporally with the third major episode of shortening in the Sevier fold and thrust belt, when the Hogsback thrust added ~21 km of shortening to become the easternmost major thrust in southwest Wyoming and northern Utah. A remarkable attribute of the RMF is that it maintained its position through multiple orogenies and changes in orientation and strength of tectonic stresses. During the Laramide orogeny, the RMF marked a tectonic boundary beyond which major contractional partitioning of the Cordilleran foreland was unable to penetrate. However, the nature of the lithospheric fl aw that underlies the RMF is an unanswered question.