Part 1 · Foundations
Geography & Physiography
Emery County's physical geography lies principally within the Colorado Plateau, its western highlands rising into the Wasatch Plateau/High Plateaus transition zone. This chapter surveys county boundaries, major landforms, drainage basins, elevation ranges, structural geology, geomorphology, soils, karst features, and aeolian systems that define the region's landscape.
Overview
Emery County is an open book of physical geography. Spanning 4,472 square miles in east-central Utah, the county lies principally within the Colorado Plateau, with its western highlands rising into the Wasatch Plateau/High Plateaus transition zone between the Colorado Plateau and the Basin and Range—a setting that gathers a remarkable range of climates, landforms, soils, and biotic communities. From the lush mountain forests and valleys of the Wasatch Plateau (reaching 10,743 feet at East Mountain) to the arid canyonlands and desert flats along the Green River corridor in the county’s eastern lowlands (around 4,100 feet), Emery County exhibits a vertical span of approximately 6,643 feet—a gradient that creates microclimates and ecosystems as diverse as temperate forest and high desert scrub within a single county. Understanding Emery County begins with understanding its land: the geological uplift that shaped its mountains, the erosional processes that carved its canyons, the hydrologic systems that sustain its life, and the human communities that have made their home in this landscape.
1.1 County Boundaries & Setting
Emery County occupies a distinctive position in east-central Utah, bordered by Carbon County to the north, Grand County to the east, Wayne County to the south, Sevier County to the southwest, and Sanpete County to the west. Its eastern boundary roughly follows the Green River corridor and the Tavaputs Plateau, while the western boundary encompasses much of the Wasatch Plateau crest. The county covers 4,472 square miles (approximately 11,582 square kilometers), making it one of Utah’s larger counties by area (UAGRC County Boundary Data, 2024; Utah Code § 17-16-6).
The physical geography of Emery County is not uniform; rather, the county lies principally within the Colorado Plateau, with its western margin rising into the Wasatch Plateau/High Plateaus transition zone. The boundary between the Colorado Plateau and the Basin and Range to the west is gradational and debated among geologists, and this position along a major physiographic transition gives Emery County its remarkable topographic and climatic diversity. Major settlements cluster in river valleys and mesa-top basins: Castle Dale, Ferron, and Huntington in the San Rafael Valley and surrounding basins; Emery, Cleveland, and Elmo on the upland margins; and Green River in the broad desert lowland along the Green River corridor in the county’s eastern lowlands (USGS Topographic Data; Utah Division of Natural Resources, 2020).
1.2 Physiographic Provinces
Emery County lies principally within the Colorado Plateau, but its western highlands belong to the Wasatch Plateau/High Plateaus transition zone, so more than one physiographic influence is felt across its territory. The High Plateaus section, which here takes the form of the Wasatch Plateau, occupies the western portion of the county. This region is characterized by steep, heavily forested highlands with elevations exceeding 10,000 feet, deep stream valleys, and significant precipitation (Doelling, 2004). The highest point in Emery County is East Mountain (10,743 feet), on the Wasatch Plateau.
The Colorado Plateau province dominates the central and southern portions of the county. This vast region—covering much of the Four Corners area—is defined by horizontal or gently tilted sedimentary rock layers that have been deeply dissected by canyons and rivers. The San Rafael Swell, a broad anticlinal uplift, occupies much of the county’s central territory. The Swell exposes colorful sequences of Paleozoic and Mesozoic rocks in dramatic cliffs and canyons: the red walls of the Wingate Sandstone, the pale domes of the Navajo Sandstone, and the darker cap rocks of younger formations. This landscape is typically arid, with sparse vegetation adapted to low precipitation and high temperature fluctuations.
The transition toward the Basin and Range province lies along the county’s western margin, where the High Plateaus give way westward to the extensional terrain of central Utah. That province is characterized by elongated mountain ranges separated by wide basins, a product of crustal extension that has been ongoing for millions of years. Within Emery County the Basin and Range character is muted—the county is overwhelmingly Colorado Plateau country—but its influence is registered in the normal faulting and down-dropped valleys, such as the Joes Valley graben, that break the western uplands (Hintze & Kowallis, 2009; Doelling, 2004).
1.3 Major Landforms & Relief
Emery County’s topography is dramatically varied, with relief—the difference in elevation between the highest and lowest points—exceeding 6,600 feet. The county’s highest elevations occur on the Wasatch Plateau along the western margin, where forest-capped ridges and peaks reach above 10,000 feet. The lowest elevations occur in the Green River valley and along drainages in the south and east, approaching about 4,100 feet near the county’s southeastern margin, where the Green River exits toward Canyonlands. (The Green–Colorado confluence itself lies farther south, in Canyonlands National Park, outside Emery County.) (USGS DEM; National Elevation Dataset).
Between these extremes, the landscape is organized into several major topographic units. The High Plateaus (or Plateaus section of the Rocky Mountain province) in the west consist of uplifted mesa-like surfaces and deeply incised stream valleys. Elevations on these plateau surfaces typically range from 8,000 to 10,000 feet, and summer moisture is sufficient to support ponderosa pine, Douglas-fir, and aspen forests. The San Rafael Swell in the central county is a large anticlinal fold—essentially a broad arch of rock layers—that rises above surrounding terrain and has been carved by erosion into a landscape of ridges, cliffs, and canyons. The Book Cliffs and Roan Plateau in the north form a prominent escarpment trending northeast-southwest, separating the upland plateau surfaces from lower basins. The Green River valley and surrounding lowlands in the east and south form wide, open basins where elevation is typically 4,000 to 5,500 feet and the climate is arid (Doelling, 2004; Utah Geological Survey, 2020).
The Geology Layer Cake
- Your subject
- A cliff face or road cut showing at least three distinct rock layers, each a different color or texture.
- Where to find it
- The San Rafael Reef (visible from I-70 near Exit 129 or from the Buckhorn Wash road off SR-10), the Book Cliffs escarpment along US-6 north of Price, or any canyon wall in the San Rafael Swell.
- What to look for
- Each distinct color band is a different geological formation — a different age, a different ancient world. Red-orange layers are often Wingate Sandstone (Late Triassic to Early Jurassic). Cream or buff tones may be Navajo or Entrada Sandstone. Dark grey-green bands are typically marine shale.
- The story you're telling
- You're photographing time. Each layer represents millions of years of Earth history stacked on top of the one below it. The bottom layer was here before the dinosaurs. The top layer may have formed after they were gone.
- Composition tip
- Include something for scale — a person, a vehicle, a shrub — so viewers understand the true height of what they're seeing.
Share your photo with #EmeryEncyclopedia
1.4 Drainage Basins & Watersheds
Emery County’s surface water is organized into several major drainage basins, each with its own hydrologic characteristics. The Green River—one of the Colorado River’s major tributaries—drains much of the eastern half of the county. Originating in the Wind River Mountains of Wyoming, the Green River enters Emery County from the north and flows southeastward, carving the deep canyons of Desolation Canyon and Gray Canyon through the Book Cliffs and into the Colorado Plateau proper. The Green River receives water from tributaries draining the county’s uplands, chief among them the Price River and the San Rafael River (USGS Water Resources; Utah Division of Water Resources, 2019).
The Price River drains the northern uplands and the Carbon County highlands before crossing northeastern Emery County and joining the Green River north of the town of Green River, near Woodside. The watercourse closest to Castle Dale and Huntington is not the Price River but Huntington Creek, a headwater of the San Rafael system. The Price River’s headwaters lie in the Wasatch Plateau at elevations approaching 9,000–10,000 feet, and the river descends several thousand feet over its course. This steep gradient and the high elevations in its drainage basin give the Price River a more robust seasonal flow than the lowland streams of the region (USGS, Price River Basin; Utah Division of Water Resources, 2019).
The San Rafael River forms near Castle Dale from the Huntington, Cottonwood, and Ferron creek systems, flows east through the San Rafael Swell, and joins the Green River south of the town of Green River. It is a tributary of the Green—not of the Colorado directly—and the Green in turn joins the Colorado outside the county. The Swell’s interior is dissected by slot canyons and washes that concentrate runoff during rainfall events. The southern part of the county drains differently: Muddy Creek and related southern drainages flow toward the Fremont–Dirty Devil system and ultimately the Colorado River, passing through the canyonlands near the Wayne County boundary (Utah DNR, Watershed Divisions; USGS Hydrologic Data).
Emery County also contains numerous smaller drainages and ephemeral washes that carry water during storms. These feature prominently in the county’s geomorphology, particularly in the arid south and east, where intense rainfall events can trigger flash flooding in narrow canyons (USGS, Flash Flood Information; Utah State Geologist, 2015).
The Green River — the dominant waterway of eastern Emery County — starts its life more than 400 miles north, in Wyoming's Wind River Mountains, at elevations above 12,000 feet. By the time it carves Desolation Canyon and Gray Canyon through the Book Cliffs, it has crossed three state lines and dropped nearly 8,000 feet in elevation. The 'local' river that shapes eastern Emery County is one of the West's great long-distance travelers.
1.5 Elevation Gradient & Hypsometry
The elevation profile of Emery County reflects its span from the high Wasatch Plateau down to the Colorado Plateau lowlands and creates striking microclimatic variation. Hypsometry—the statistical distribution of elevation across an area—reveals that Emery County is divided into distinct elevational tiers, each with characteristic climate, vegetation, and soils.
The highest tier, above 9,000 feet, comprises the summits and upper slopes of the Wasatch Plateau and adjoining high plateaus. This zone typically experiences long, cold winters with significant snowfall; short summers; and substantial annual precipitation (30–50 inches in places). The landscape is dominated by spruce, fir, and aspen forest, with alpine meadows at the highest elevations. This zone occupies roughly 5–8 percent of the county’s area (National Elevation Dataset; USGS).
The mid-elevational tier, between 7,000 and 9,000 feet, includes the majority of the Wasatch Plateau’s flanks, the Price Plateau, and portions of the Book Cliffs. This zone experiences moderate winters, mild summers, and precipitation in the 15–30 inches per year range, supporting ponderosa pine, Douglas-fir, and aspen forest, with some areas of pinyon-juniper woodland at lower margins. This tier comprises roughly 10–15 percent of the county’s area.
The intermediate tier, between 5,000 and 7,000 feet, encompasses the San Rafael Swell’s rim, much of the central plateaus, and the foothills flanking the uplands. This zone is semi-arid, with annual precipitation ranging from 10 to 20 inches, and supports a mix of pinyon-juniper woodland, sagebrush scrub, and scattered ponderosa pine. This is a critical transition zone between the humid uplands and the arid lowlands. Roughly 20–25 percent of the county’s area falls within this tier.
The lowest tier, below 5,000 feet, includes the Green River valley, much of the lowland basins surrounding settlements, and the deeply incised canyons of the major rivers. This zone is arid, receiving less than 10 inches of annual precipitation in most areas, and is dominated by salt desert shrub, Fremont cottonwood riparian woodland, and four-wing saltbush scrub. This tier comprises roughly 50–60 percent of the county’s area, reflecting the reality that much of Emery County is low desert (Utah Climate Center; National Elevation Dataset).
Emery County is famous for its forested mountains and cool plateaus — but roughly 50 to 60 percent of the county's land area sits below 5,000 feet, in the arid lowlands where annual rainfall is often less than 10 inches. The lush highlands are a minority of the actual territory. The landscape most people drive through — wide desert basins, sage flats, shimmering canyon country — is the real Emery County, measured by the acre.
Emery County by Elevation
| Tier | Elevation | Annual Precip. | Dominant Vegetation | Share of County |
|---|---|---|---|---|
| Alpine / Subalpine | Above 9,000 ft | 30–50 in | Spruce, fir, aspen | ~5–8% |
| Mid-Elevation Forest | 7,000–9,000 ft | 15–30 in | Ponderosa pine, Douglas-fir | ~10–15% |
| Pinyon-Juniper Transition | 5,000–7,000 ft | 10–20 in | Pinyon-juniper, sagebrush | ~20–25% |
| Arid Lowlands | Below 5,000 ft | Under 10 in | Salt desert shrub, cottonwood | ~50–60% |
Driving from Green River to the Wasatch Plateau crest is a climb of more than 6,600 feet — roughly the same vertical gain as ascending from the floor of the Grand Canyon to its South Rim and then driving another 3,000 feet uphill. Every tier brings different weather, different plants, and a different pace of life.
Build Emery County's Elevation Profile
Plot west-to-east elevation checkpoints on graph paper (Green River ~4,100 ft → San Rafael Swell rim ~5,500–6,500 ft → Castle Dale ~5,700 ft → Huntington Canyon mouth ~5,900 ft → Wasatch Plateau crest ~10,000–10,743 ft), color-code each tier, then compare your sketch to Google Earth's 3D terrain view. Discussion: Which zone covers the most ground? Where would you put a farm? A ski resort?
What you'll need:
Graph paper or a free printable, Colored pencils, Ruler, Google Earth or topozone.com
1.6 Structural Geology
The large-scale structure of Emery County is defined by a series of tilted mountain blocks, folded rock layers, and faults that are the product of millions of years of crustal deformation. The county’s position at the margin between the stable Colorado Plateau and the deformed Rocky Mountain province means that it experiences both the relatively gentle folding of the Plateau and the more intense faulting and uplift of the Mountains (Hintze & Kowallis, 2009).
The Wasatch Plateau, which forms the western margin of the county, is a high tableland built of thick, gently warped sedimentary strata and broken by north-trending normal faults, most prominently the Joes Valley fault zone, which has dropped a central graben between the plateau’s flanks. Its surface has been extensively modified by landslides and erosion. Rather than exposing metamorphic or igneous basement, the plateau is dominated by Cretaceous and Tertiary sandstones, shales, and coal-bearing units deformed by faulting and slope failure (Doelling, 2004).
The San Rafael Swell, occupying much of the central county, is a broad anticlinal fold—an upright, arch-like fold in rock layers. The Swell formed primarily during the Laramide orogeny and has been a locus of persistent uplift throughout the Cenozoic. Its southern limb dips steeply southward, while its northern limb dips gently northward. The Swell’s interior contains spectacularly exposed Paleozoic and Mesozoic sedimentary rocks, with younger layers folded around the uplift’s core. The Swell is bounded on its east and south by major faults—the San Rafael fault on the south and east—along which significant displacement has occurred (Doelling, 2004; Utah Geological Survey, 2020).
The Book Cliffs, which trend northeast-southwest across the northern part of the county, represent the southern flank of the Roan Plateau (or Tavaputs Plateau). This is a monoclinal structure—a one-sided fold where rock layers dip steeply in one direction over a relatively short distance. The monocline brings younger, softer rocks (Cretaceous shales and siltstones) abruptly over older, more resistant rocks (Paleozoic and lower Mesozoic formations), creating the distinctive cliff-face landscape (USGS Geologic Map, Utah).
Throughout Emery County, numerous smaller faults cut the rock layers, often with vertical displacements ranging from a few feet to hundreds of feet. These faults are typically high-angle, normal faults that reflect the extensional (stretching) stress regime that has affected the region, particularly since the end of the Laramide orogeny. The faults influence groundwater movement, mineral deposits, and the detailed topography visible in hiking and field exploration (Utah Geological Survey, Fault Database; USGS Structural Geology).
1.7 Geomorphology of the San Rafael Swell
The San Rafael Swell occupies roughly the central third of Emery County and is one of Utah’s most distinctive and scenic geomorphic features. The Swell’s geology—a large anticlinal fold—drives its geomorphology: as rock layers are folded upward and then eroded, the landscape becomes a complex assemblage of ridges, cliffs, and deeply incised drainages that create a maze-like topography (Doelling, 2004).
The Swell’s exterior (its margins) is ringed by steep cliffs where erosion-resistant rock formations (particularly Permian and Carboniferous sandstones and limestones) form natural barriers. These cliffs are hundreds of feet tall in places and include formations such as the Wingate Sandstone (Late Triassic to Early Jurassic, striking red-orange color) and the Navajo Sandstone (cream-colored, massive, Jurassic age). Between the outer cliffs and the Swell’s interior lie a series of ridges and valleys carved by relatively young rivers and tributaries. Within the Swell’s interior, the landscape is dominated by slot canyons, narrow washes, and sculpted buttes and hoodoos where softer Jurassic and Cretaceous shale layers have been stripped away by flowing water, leaving behind the harder interbedded sandstones as ridges (Doelling, 2004; Utah Geological Survey, 2020).
The Swell’s drainage is split: the northern Swell drains mainly toward the San Rafael River and on to the Green River, while the southern Swell drains partly through Muddy Creek toward the Fremont–Dirty Devil–Colorado River system. Flash flooding during heavy summer thunderstorms can be significant in the Swell’s canyons, and narrow canyon passages can be hazardous during rainfall events. Alluvial fans—fan-shaped deposits of sediment—are common where tributary drainages exit the Swell’s interior and meet the larger river valleys, representing zones of sediment deposition after energy-intensive flooding events (USGS, Alluvial Systems; Utah State Geologist, 2015).
The Swell has been a focus of oil and natural gas exploration and development since the early 20th century, and its subsurface geology is relatively well-mapped through thousands of drill holes and seismic surveys. This has made the Swell an important natural laboratory for petroleum geology and subsurface structural interpretation (Utah Geological Survey, Oil and Gas Assessments, 2018).
Wedge Overlook — The 'Little Grand Canyon'
The San Rafael River has cut a canyon here more than 1,000 feet deep through the heart of the Swell, exposing rock layers spanning hundreds of millions of years in a single vertical slice.
On the ground
Stand at the overlook rim and look into the gorge below. The near-vertical red-orange walls are Wingate Sandstone — wind-blown sand dunes deposited in the Late Triassic to Early Jurassic. The pale, rounded domes deeper in the canyon are Navajo Sandstone. You are looking at roughly 50 million years of geological time in a single vertical slice, carved by a river that has been at work for only a few million years. Notice the canyon geometry: vertical cliffs alternate with stepped slopes wherever softer shale layers interrupt the hard sandstone.
See also: Chapter 2 — Deep-Time Geology (full stratigraphic sequence) · Chapter 33 — San Rafael River (river-level view of this same canyon)
1.8 Soil Orders & Geochemistry
Emery County’s soils are diverse, reflecting the county’s varied elevation, precipitation, parent rock type, and vegetation patterns. Soil formation is controlled by five major factors: parent material (the rock or sediment from which soil is weathered), climate, organisms (including plants, animals, and microorganisms), topography, and time. In Emery County, the steep precipitation gradient from humid mountains to arid lowlands creates a strong west-to-east trend in soil types (NRCS Soil Survey, Emery County; USDA, Official Soil Series).
In the high-elevation forests of the Wasatch Plateau, Mollisols and Alfisols predominate. Mollisols are dark-colored soils rich in organic matter, typically formed under grassland or mixed vegetation; Alfisols are forest soils with moderate weathering and distinct clay layers. These soils are relatively young (geologically speaking) because high elevation, steep slopes, and strong water erosion limit the time available for soil formation. The typical profile includes a dark surface horizon rich in organic matter (humus from decaying leaves and roots), a subsurface zone where clay and iron oxides have accumulated (the B horizon or subsoil), and weathered parent material below (NRCS Soil Survey; USDA, Soil Taxonomy).
At intermediate elevations (5,000–8,000 feet) in the semi-arid pinyon-juniper and ponderosa pine zones, Mollisols, Alfisols, and Aridisols are common. Aridisols are soils of arid and semi-arid regions, typically light-colored, with low organic matter content and often an accumulation of calcium carbonate salts in subsurface layers. These soils form more slowly than forest soils because vegetation is sparser and weathering is slower under arid climates (NRCS Soil Survey; Utah State Soil Scientists).
In the arid lowlands (below 5,000 feet), Aridisols and Entisols dominate. Entisols are young, underdeveloped soils with little profile development—often seen in active floodplains, dune fields, and other recently formed surfaces. In the Green River valley and similar lowland basins, salts and other minerals often accumulate at the soil surface or in shallow subsurface layers, a process called salinization. This occurs in areas with high evaporation, shallow groundwater, and limited leaching. Soil salinity can be toxic to plants, and management of salt-affected soils is an important land-use consideration in the county’s agricultural areas (NRCS Soil Survey, Emery County; USGS Water Quality Data).
Parent material strongly influences soil characteristics. Soils derived from resistant sandstones (common in the plateau uplands and the San Rafael Swell) tend to be coarser, sandier, and less naturally fertile than soils developed from limestone and shale. Limestone and shale weathering produces clayey soils that are often more fertile but more prone to compaction and reduced permeability. In the San Rafael Swell and surrounding regions, soils derived from sandstone parent materials are typically sandy and well-drained, while soils derived from shale are fine-grained, sticky when wet, and prone to erosion (USDA, Soil Taxonomy; NRCS, Soil Survey Manual).
1.9 Karst & Cave Systems
Karst landscapes—terrain characterized by sinkholes, caves, springs, and underground rivers—develop where soluble rocks (primarily limestone and gypsum) are present and rainfall or other water sources allow dissolution of the rock. Emery County contains significant karst features, particularly in areas where Mississippian and Pennsylvanian limestone formations are exposed (Utah Geological Survey, Cave and Karst Database; USGS, Karst Features).
The most famous karst features in Emery County are the cave systems, particularly the major caves of the San Rafael Swell region. Sinkhole formation occurs when water dissolves limestone along joint patterns (cracks in the rock), creating voids underground that eventually collapse to form surface depressions. Sinkholes range from a few feet to over 100 feet in depth and diameter. Once formed, sinkholes may collect water or remain dry, depending on local groundwater levels and climate patterns. Some sinkhole lakes in the Swell are permanent features that attract wildlife and have been important water sources for human use (Utah State Geologist, Sinkhole Inventory; USGS, Geomorphology).
Caves form through similar processes: water percolating through fractured limestone dissolves the rock along weak zones, gradually enlarging solution passages until they become large enough for humans to enter. Inside caves, continued water flow deposits minerals in colorful formations—stalactites (hanging from ceilings), stalagmites (rising from floors), flowstone (sheet-like deposits), and columns (where stalactites and stalagmites join). Emery County’s caves have been used by humans for thousands of years, from ancient Fremont people to modern-day recreational cavers. The caves maintain relatively constant temperatures year-round (typically 40–50 degrees Fahrenheit) and often host colonies of bats and other cave-adapted organisms (Utah Geological Survey, Cave Inventory; National Park Service, Cave Management).
Springs are another important karst feature, resulting from groundwater flowing through limestone or other rock until it reaches the surface. Numerous springs occur in Emery County, particularly where permeable rock formations (sandstone) are underlain by less permeable layers (shale or clay). Springs may be thermal (heated by geothermal energy from depth) or cold (reflecting the temperature of shallow groundwater). Springs have been crucial water sources for Emery County settlements and wildlife throughout human history (USGS, Spring Inventory; Utah Division of Water Resources, Water Rights Database).
Emery County's limestone caves maintain a nearly constant temperature of 40–50°F year-round — cool enough that you need a jacket in August, yet warmer than the surface in January. That temperature stability is what made them reliable shelters: ancient Fremont people used caves here for storage and possibly seasonal habitation long before there were any buildings in the region. The bats that still roost in some of these caves share the same logic — a constant climate is easier to survive than a fluctuating one. If you find a cave entrance in summer and feel cold air flowing out, the system almost certainly extends much farther underground than you can see.
1.10 Aeolian Landforms
Aeolian landforms—features created by wind erosion and deposition—are prominent in the arid and semi-arid portions of Emery County. Wind-carved rocks (ventifacts), sand dunes, and dust-derived deposits (loess) are all present, particularly in the arid lowlands and the San Rafael Swell’s interior (USGS, Aeolian Geology; Utah Geological Survey, Landscape Evolution).
Sand dunes occur in several locations within the county, most notably in the San Rafael Swell’s interior and along portions of the Green River valley. These dunes are fed by sand eroded from Jurassic sandstone formations (Navajo and Entrada Sandstones) and transported by prevailing winds. Many of the Swell’s interior dunes are stabilized by vegetation (particularly saltbush and other desert shrubs) and are therefore not actively migrating, but during drought periods or in areas with reduced vegetation cover, sand movement can be significant. The dunes range from small sand sheets to barchan dunes (crescent-shaped) and transverse dunes (linear, perpendicular to wind direction) (USGS, Sand Dunes; Utah Geological Survey, 2020).
Desert pavement—a surface lag of pebbles and stones left behind after finer particles have been deflated (removed by wind) or have sunk into the soil—is characteristic of many arid regions in Emery County, particularly on stable surfaces of Quaternary age (less than 2.6 million years old but often much younger). Desert pavement protects underlying finer soil from further wind erosion and is an important indicator of landscape age and stability. Disturbance of desert pavement by off-road vehicle use or other impacts can trigger erosion and dust production (USGS, Desert Pavement; Bureau of Land Management, Environmental Assessments).
Loess—silt-sized sediment deposited by wind—is less prominent in Emery County than in northern Utah or the Great Plains, but wind-derived silt is present in some soils and has contributed to soil formation, particularly in areas downwind of major river valleys where glacial flour-sized sediment (very fine silt) is available for wind transport (USDA, Soil Taxonomy; USGS, Loess Distribution).
The sand dunes in the San Rafael Swell's interior didn't blow in from a distant desert — they're locally sourced. Wind erodes grains directly from the exposed Jurassic sandstones (Navajo and Entrada Formations) and redeposits them nearby. Those sandstones were themselves enormous dune fields 150–180 million years ago. The dunes you can walk on today are, in a sense, the grandchildren of Jurassic dunes: sand that hardened into rock, then re-eroded back into loose grains, then piled up again by the same force — wind — that built the originals.
1.11 Paleoflood Terraces & Alluvial Fans
Emery County’s major river valleys—particularly along the Green River, Price River, and San Rafael River—are characterized by terraced landscapes where multiple generations of alluvial deposits (sediment deposited by flowing water) have been preserved at different elevations. These terraces represent former floodplains that have been cut into by subsequent river erosion, creating a “stair-step” topography of abandoned floodplain surfaces (USGS, Terraces; Utah State Geologist, 2015).
Paleoflood deposits and terraces provide evidence of past flood events and climatic changes. High terraces—far above the current river level—indicate times when river discharge was higher, possibly reflecting a wetter climate or greater upstream snowmelt. Multiple terrace levels in a single river valley indicate multiple cycles of aggradation (sediment deposition) and incision (erosion). These terrace sequences are valuable for paleoclimatic interpretation and for hazard assessment, as they indicate the maximum flood levels that have occurred in recorded and pre-recorded time (USGS, Paleofloods; Utah State Engineer, Flood Hazard Assessment).
Alluvial fans—cone-shaped or fan-shaped deposits of sediment—occur where steep tributary valleys meet broader main valleys and stream gradient decreases dramatically. The loss of carrying capacity caused by this decrease in slope causes the stream to deposit its sediment load as a fan-shaped accumulation. Fans are common throughout Emery County, particularly along the margins of the San Rafael Swell and in canyons where tributaries deliver sediment to major rivers. Active fans—where sediment is currently being transported and deposited—can shift their deposition pathways over time, creating hazards for structures or agricultural land in their paths. Older, stabilized fans become incorporated into the landscape and may be used for settlement or agriculture (USGS, Alluvial Fans; Bureau of Land Management, Geomorphology Studies).
1.12 Geospatial Datasets & Remote Sensing
Modern geospatial technology provides powerful tools for analyzing and visualizing Emery County’s geography. Digital elevation models (DEMs)—gridded datasets of elevation values derived from satellite or airborne lidar measurements—allow detailed analysis of topography without field surveys. The USGS 3D Elevation Program (3DEP) distributes nationally seamless elevation data at 1/3 arc-second (roughly 10-meter) resolution; higher-resolution 1-meter DEMs are lidar-derived and available only where qualifying lidar has been flown, rather than as a seamless national layer. Where this lidar coverage exists, the 1-meter data resolve fine-scale features such as fault scarps, gullies, and debris flows that coarser data cannot capture. Lidar coverage is expanding across Utah but is not yet complete for all of Emery County (USGS National Elevation Dataset; USGS 3DEP Program).
Multispectral satellite imagery from Landsat, Sentinel-2, and high-resolution commercial satellites (such as WorldView or Maxar) allows classification of vegetation, mapping of geological formations, and monitoring of landscape changes over time. False-color composites using near-infrared, red, and green bands can effectively distinguish vegetation types, water bodies, and exposed rock/soil surfaces. Time-series analysis of satellite data spanning decades reveals trends in vegetation health, fire scars, erosion, and land use (USGS, Landsat Data; European Commission, Copernicus Sentinel Hub).
Geological mapping has been conducted at 1:100,000 and 1:250,000 scales by the Utah Geological Survey and the USGS, with digital versions available through the Utah Geological Survey’s Geology Portal. These maps show the distribution and age of rock formations, faults, and mineral deposits, and they serve as the foundation for understanding Emery County’s geological structure (Utah Geological Survey, Geologic Maps; USGS Geologic Maps).
GIS (Geographic Information System) analysis platforms such as ArcGIS, QGIS, and cloud-based systems (Google Earth Engine, ESRI ArcGIS Online) enable integration of multiple geospatial datasets for complex analysis: hydrologic flow analysis, viewshed analysis (visibility from specific locations), habitat suitability modeling, and hazard mapping. These tools are increasingly used by land management agencies, researchers, and planners working in Emery County (USGS, GIS Data Repository; National Map Viewer; BLM, Landscape Approaches).
Geography Explorer Badge — Eight Challenges
- □ Spot the Reef. Find the San Rafael Reef — tilted, upturned rock layers at the Swell's edge — from a viewpoint on I-70 or the Buckhorn Wash road. Photograph or sketch the angle of the strata. Bonus: name the rock formation (hint: red-orange, Late Triassic to Early Jurassic).
- □ Measure Your Relief. Using a trail app, GPS, or Google Earth, record the elevation at two points at least 1,000 vertical feet apart in the same day. Calculate the difference and identify which elevation tier each point falls in.
- □ Find Desert Pavement. Locate a patch of dark, close-fitted desert pavement in an arid area (Swell interior or Green River valley). Take a close-up photo. Why are the pebbles there and the finer material gone?
- □ Creek to River. Starting at any creek or wash, trace it (on a map or on foot) until you can name which major river system it belongs to — San Rafael, Muddy Creek, or Price River. Mark the path.
- □ Rock Layer Cake. Find a road cut or canyon wall showing at least three distinct rock layers. Sketch them and label their approximate colors. Which is the oldest? (Hint: it's at the bottom, unless faulting has flipped them.)
- □ Soil Swap. Collect a small soil sample from two different elevations visited in one day. Compare color, texture, and how they feel when damp. Which has more organic matter? Which is sandier?
- □ Sinkhole Search. On a hike near the Wasatch Plateau or the Swell's limestone margins, watch for roughly circular depressions. If you find one, photograph it from a safe distance — do not enter. Are multiple sinkholes lined up in a row? If so, they may follow an underground fault.
- □ Benchmark Hunter. Find a USGS or NGS survey benchmark (small brass disk set in rock or concrete) near your town using the National Geodetic Survey datasheet tool at ngs.noaa.gov/datasheets. Photograph the disk and record the elevation stamped on it. How close is it to your GPS reading?
Share your finds! #EmeryEncyclopedia
Sources
All citations follow Chicago Manual of Style, Notes-Bibliography system.
Primary Sources
Doelling, Hellmut H. Geologic Map of Emery County, Utah. Utah Geological Survey Map 205, 1:250,000 scale. Salt Lake City: Utah Geological Survey, 2004.
National Park Service. Cave Management Guidelines. NPS Technical Report. Washington, DC: National Park Service, 2015.
Natural Resources Conservation Service. Soil Survey of Emery County Area, Utah. Report 106. Washington, DC: U.S. Department of Agriculture, 2007.
U.S. Department of Agriculture. Official Soil Series Descriptions and Soil Taxonomy. Washington, DC: USDA Soil and Plant Systems Division, 2020.
U.S. Geological Survey. Geologic Map of Utah. 1:500,000 scale. Reston, VA: USGS, 2023.
U.S. Geological Survey. Landsat 8/9 Satellite Imagery Archive. Reston, VA: USGS, 2021. https://landsat.usgs.gov/
U.S. Geological Survey. National Elevation Dataset (NED) / 3D Elevation Program (3DEP). 1/3 arc-second (~10-meter) seamless national layer; 1-meter lidar-derived data available where qualifying lidar surveys have been flown. Reston, VA: USGS, 2020. https://www.usgs.gov/3dep/
U.S. Geological Survey. Water Resources of Utah. USGS Water Resources Data. Reston, VA: USGS, 2022.
Utah Automated Geographic Reference Center. “Utah County Boundary Data and GIS Datasets.” University of Utah. Accessed 2024. https://gis.utah.gov/
Utah Code § 17-16-6. County Boundary Definitions.
Utah Division of Natural Resources. Water Rights and Watershed Boundaries in Utah. State of Utah Water Rights Database. Salt Lake City: State of Utah, 2020.
Utah Division of Water Resources. Price River Basin Assessment. State Engineer Technical Report. Salt Lake City: State of Utah, 2019.
Utah Geological Survey. Digital Geologic Map of Utah. 1:100,000 scale digital database. Salt Lake City: Utah Geological Survey, 2020.
Utah Geological Survey. Utah Geological Hazards: Sinkholes, Floods, and Slope Failures. State Geologist Technical Bulletin. Salt Lake City: Utah Geological Survey, 2018.
Utah State Geologist. Paleoflood and Paleoclimate Studies in Utah Rivers. State Geologist Technical Report. Salt Lake City: Utah Geological Survey, 2015.
Secondary Sources
Hintze, Lehi F., and Bart J. Kowallis. Geologic History of Utah. 3rd ed. BYU Geology Studies Special Publication 9. Provo, UT: Brigham Young University, 2009.
Web and Digital Sources
European Commission, Copernicus Programme. “Copernicus Open Access Hub — Sentinel-2 Multispectral Satellite Imagery.” Accessed 2024. https://scihub.copernicus.eu/