An In-depth Look at Ogden Valley’s Groundwater


An In-depth Look at Ogden Valley’s Groundwater

by J. Lucy Jordan

Groundwater—water that flows in the spaces between rock and soil particles—is vitally important as a pristine drinking water source for Ogden Valley and Ogden City residents. Surface water—water in Ogden Valley’s streams and reservoirs—is equally important to the valley’s residents for irrigation and to Ogden City to supplement its water supply. The two systems are intimately connected in Ogden Valley, as a new study by the Utah Geological Survey (UGS Special Study 165) has revealed.

This new research brought up several important questions about the Ogden Valley groundwater–surface-water system, such as: When a 3-mile reach of stream loses the volume of an Olympic-sized swimming pool every 90 minutes, where does that water go? How can young groundwater be found under a mostly impenetrable clay layer? Should septic tanks continue to be installed for sewage waste disposal in Ogden Valley? This article touches on the answers presented in the new report.

Compared to many watersheds in Utah, Ogden Valley has plentiful water resources. Several large streams drain to Pineview Reservoir, providing most of the valley with adequate irrigation water. The mountains surrounding the valley are composed largely of carbonate and conglomerate rocks that make adequate aquifers, and the principal valley-fill aquifer is thick and productive. However, urban and residential development of agricultural land is causing concern about interference with existing water rights and impacts to water quality. The UGS used state-of-the-art tools to better define the quantity and quality of the groundwater in Ogden Valley and understand the connection between surface water and groundwater.

Oblique aerial view of Ogden Valley showing outcrop of aquifer and confining units.

Scientists use stable isotopes of hydrogen and oxygen in water to determine the source of groundwater and how groundwater interacts with surface water. In our study, we analyzed these isotopes in hundreds of well and surface water samples collected at various times throughout the year, which provided enough data to be able to tease out small differences in the stable isotope ratios of waters across the valley. The results show that, on average, roughly half the water in the upper part of the principal aquifer is recharged by precipitation or streams on the valley floor and half comes from recharge high in adjoining mountains. We could see even more detail between sub-watersheds— groundwater underlying the South Fork drainage gets 60 percent of its recharge from surface water, whereas the North Fork drainage gets only about 30 percent from surface water. This quantification will help water managers foresee potential impacts to existing water users if points of water use are moved from one location to another and highlights the need to protect groundwater from contamination that may be present at or near the surface.

The results of seepage runs, in which we measured streamflow at many points along streams and canals to discern where water seeps from the ground into the stream or vice versa, corroborate the findings from the stable isotope research. The boulder and cobble streambed of the South Fork Ogden River is where we measured a volume of water equivalent to an Olympic-sized pool seeping into the aquifer every 90 minutes (17 cubic feet per second or cfs). Aggregating our seepage run data throughout Ogden Valley, we estimate that streams lost on average 12,000 acre-feet of water during baseflow conditions (July through February) and gained 15,000 acre-feet during spring runoff. The Ogden Valley Canal loses about half its flow during the height of the irrigation season, and that water recharges the principal aquifer. This dynamic interplay between streams and groundwater is possible because the water table fluctuates near the base of the stream channels. A lowered water table resulting from increased pumping or reduced streamflow could have negative impacts to the system, shunting water Gaining (blue) and losing (red) reaches of major streams during a March 2016 seepage run and estimated net gain or loss from March through June (runoff season) from three sub-basins. During baseflow, nearly all the gains estimated during the runoff season, shown here, are lost back to the aquifer. The streams and aquifers are actively exchanging water but are generally in balance each year. that currently flows to the shallow unconfined aquifer and Pineview Reservoir to deeper parts of the confined aquifer.

Gaining (blue) and losing (red) reaches of major streams during a March 2016 seepage run and estimated net gain or loss from March through June (runoff season) from three sub-basins. During baseflow, nearly all the gains estimated during the runoff season, shown here, are lost back to the aquifer. The streams and aquifers are actively exchanging water but are generally in balance each year.

Understanding the amount of groundwater flow into Pineview Reservoir is important to evaluating reservoir water quality and quantifying groundwater in Ogden Valley. We used a simple mass balance approach in which we quantified known flows into and out of the reservoir and solved for net groundwater flow to or from the reservoir. By integrating our stable isotope analyses into the mass balance model (a new technique for us), we were able to refine the estimate of net groundwater flow through the reservoir. Net groundwater input to Pineview Reservoir in 2016 was likely 34,000 acre-feet of water. Groundwater flowing into the reservoir helps balance years having less streamflow input, which helps stabilize water supply for downstream users and recreation.

The Ogden City well field, located on a peninsula surrounded by Pineview Reservoir, has reliably produced water for a century. The wells are completed in a confined aquifer separated from the overlying reservoir and shallow aquifer by a silt and clay unit that is as much as 120 feet thick. The silt and clay confining unit would typically be expected to isolate the well field from surface water and shallow groundwater, but our samples revealed concentrations of an environmental tracer that indicate a good fraction of the well water was recharged to the aquifer less than 50 years ago. Also, the stable isotope ratio in the well water is more like that of shallow wells in the unconfined part of the aquifer than expected given the well field’s depth and location, corroborating a nearsurface recharge source. Recharge could travel relatively quickly through leaking abandoned well casings in the bottom of the  reservoir, leakage through thinner parts of the confining unit, or from the west where the distance from the edge of the confining unit to the well field is shortest. This finding illustrates that water in the confined aquifer could be vulnerable to surface contamination.

A UGS scientist measures streamflow during the March 2016 seepage study.

Hydrogeologists quantify the amount of groundwater in an aquifer system using groundwater budgets. Because directly measuring groundwater flow under the earth’s surface is impossible, we make budgets using atmospheric, streamflow, and pumping data, usually entered into a computer model that can help us quantify the volumes of water moving through different parts of the aquifer. Our water budget calculations show that the watershed receives about 540,000 acre-feet of water from precipitation on an average year. Much of that is lost to evaporation before it enters the groundwater system, leaving about 160,000 acrefeet of water to interact with streams and aquifers. The South Fork sub-basin, because it is the largest in area, has the largest percentage of the total budget. Groundwater in the valley-fill aquifer system is a fraction of the total budget. Roughly 67,000 acre-feet of water recharges the valley-fill aquifers each year. Recharge to the valley-fill aquifers is roughly one-third each from precipitation, seepage, and mountain block recharge. Roughly half of the discharge from the valley-fill aquifers flows to Pineview Reservoir, a quarter discharges as baseflow to the streams as they cross the valley fill, and most of the remaining discharge is pumped from the confined aquifer at the Ogden City well field. Recharge and discharge are generally in balance in Ogden Valley.

Most homes and businesses in Ogden Valley use septic tank soil absorption systems for indoor wastewater disposal, which add nitrogen and other waste products to the environment. The UGS evaluated the impact of septic tanks on Ogden Valley’s groundwater in 1998 and recommended that lot sizes be at least 3 acres to limit the increase in mean nitrate concentration to 1 milligram per liter (mg/L) over the thenmean concentration of 0.74 mg/L. In our current study, we found that the geometric mean nitrate concentration in the unconfined valley-fill aquifers (the aquifers that receive the bulk of septic-tank leachate) was 1.43 mg/L, still well below the allowable drinking water maximum limit of 10 mg/L, but clearly higher than in 1998. Our updated recommendation, using a smaller groundwater flow volume than was used in the 1998 study, is 4.4 to 5.8 acres minimum per system. Advanced removal septic tank systems, lagoon systems, or sewage treatment plants are options that could be used to protect Ogden Valley’s water quality if planners want to allow higher density housing development.

These are just a few of the new details we learned about the watershed and groundwater of Ogden Valley. The new 222-page report will be a useful tool for policy makers and water users to understand the potential effects of current and future water use on water supply and the environment of Ogden Valley.

J. Lucy Jordan

is a senior geologist in the Utah Geological Survey’s Groundwater and Wetlands Program. Lucy’s work with UGS over the past 15 years has focused on water-resource assessments in Utah, including water-quality studies, aquifer testing, well drilling, spring and wetland inventories, and nitrate- and salinity-compromised groundwater systems. She is currently managing a real-time surface-water flow monitoring program in western Utah and is involved in quantifying hydrological changes in small watersheds undergoing wildlife habitat restoration projects in Utah.

Is There a Wetland on Your Property? Identification and Next Steps


Is There a Wetland on Your Property? Identification and Next Steps

by Diane Menuz

The most common question we are asked in the Groundwater Program’s Wetlands Section is, “I’m thinking of buying a property but it may have wetlands on it. How do I know and what will this mean for me?” Wetlands and other aquatic features like streams and lakes are protected under the federal Clean Water Act, legislation passed in 1972 to address the rampant dumping of sewage, industrial chemicals, and other pollutants into our nation’s waters. Wetlands are integral to water quality protection because they can detain or transform pollutants that come from upland areas, thus preventing the runoff from reaching our streams and lakes. Wetlands provide a broad range of other important functions as well, including flood storage, erosion control, natural groundwater recharge areas, and wildlife habitat, as well as economic and recreational values.

Spring-fed wetland behind a residential area in Francis, Utah

Wetlands are areas that are flooded or saturated for at least part of the growing season, the period between spring and fall when plants and soil microbes are most active. Some areas are obviously wetlands — marshes with standing water or waterlogged meadows that feel squishy with each step. However, many wetlands in Utah are only wet for a short period of time in the spring and might not even be wet every year, especially during periods of drought. The U.S. Army Corps of Engineers (Army Corps), the lead regulatory agency for wetland permits in Utah, looks at three factors to determine whether an area is a wetland: (1) evidence of wetland hydrology (e.g., water or signs of water such as sediment deposits, dry algae, soil cracking, flow patterns), (2) abundance of wetland-associated vegetation (obvious species such as cattail and bulrush, but also many grasses, sedges, and other plants), and (3) hydric soil indicators (distinct soil textures and colors that form in soils that are frequently saturated). Many wetlands are tough for non-experts to identify, particularly during a drought year or in the middle of the summer.

Two good online resources can aid your investigation — the U.S. Fish and Wildlife Service’s (USFWS) National Wetland Inventory (NWI) and the Natural Resources Conservation Service’s (NRCS) National Cooperative Soil Survey. NWI data show the distribution of wetlands and other aquatic resources and the soil survey data indicate whether map units have hydric soils (e.g., soils that form in wetland conditions). However, both sets of data have their limitations. NWI data are mapped using aerial imagery with minimal field verification and may miss some wetlands entirely, and soil survey data provide information on the percent of a map unit that has hydric soil, not the exact location of areas with hydric soils. Furthermore, both sets of data are out-of-date in much of Utah and show approximate rather than exact boundaries.

NWI wetlands data and NRCS hydric soils data in Provo, Utah. Note that many areas mapped as having hydric soils are developed, and not all areas mapped as wetlands are also mapped as having hydric soils.

If you have any reason to believe there may be wetlands on a property you are considering developing, you may want to consult with the local office of the Army Corps to discuss your plans, possible impacts to wetlands and other aquatic resources, and if those resources fall within the regulatory jurisdiction of the Army Corps. They may recommend hiring a consultant to conduct a delineation to determine exact wetland boundaries and identify other aquatic resources that might be regulated under the Clean Water Act. If a permit is required, the Army Corps can walk you through what the permitting process will look like for your project. Nationwide, the Army Corps denies only 3 percent of requests for permits, but obtaining a permit will add time and cost to a project, including consulting fees for aquatic resource delineation and permit preparation and mitigation costs to compensate for impacted resources.  You also may want to find out if your local planning department has any restrictions, such as setback requirements between development and aquatic resources. If you are concerned about wetlands on agricultural land, the NRCS can conduct a delineation on the property and help you understand the applicable regulations for agricultural use.

While the UGS does not have a regulatory role in the wetland permitting process, we are working to update NWI data to provide the public with more current and spatially accurate information on the location and extent of wetlands in Utah. We have completed mapping projects in the Upper Bear River (see Survey Notes, v. 49, no. 1), on the east shore of Great Salt Lake, and around Bear Lake and have ongoing projects in the Uinta Basin and Cache County. We also maintain a web application that displays NWI data for the state with other supporting data layers to make it easier for people to find out what is mapped on their property. While the mapping work we do will never replace the need for precise field delineations, it is an important tool for conducting preliminary screenings of areas to determine whether potential wetland issues might exist.

Energy News: Covenant Oil Field in the Central Utah thrust Belt Turns 15 Years Old


Energy News: Covenant Oil Field in the Central Utah Thrust Belt Turns 15 Years Old

by Thomas C. Chidsey, Jr.

Location of Covenant oil field, play area, and selected thrust systems in the central Utah thrust belt.

Fifteen years ago Michigan-based Wolverine Gas & Oil Corporation discovered Covenant oil field about 8 miles east-northeast of Richfield, Sevier County, in a region known as the central Utah thrust belt (see Survey Notes, v. 37, no. 2). Over 100 wells had been drilled in the region with no success until the Kings Meadow Ranches No. 17-1 well tested over 700 barrels of oil per day (BOPD) making Covenant the biggest Utah discovery since 1979, when the 129-million-barrel Anschutz Ranch East field was discovered on the Utah-Wyoming border east of Coalville. Although Wolverine attempted to keep the new discovery and oil production rates confidential, it was the worst-kept secret in central Utah. Covenant field is located adjacent to State Highway 24 just a few miles from the small town of Sigurd. The drill rigs, pump jack, oil tank batteries, and assorted oil field equipment were in plain site. Tanker trucks capable of carrying 800 barrels of oil could be observed leaving the field area—and were counted by locals. It was not long before word spread of the new and very significant oil find in a region that had only frustrated geologists for decades. Farmers and ranchers in the area received large cash offers from oil companies to lease subsurface mineral rights (see Survey Notes, v. 51, no. 2). Seismic crews used helicopters, large vibroseis trucks, and dynamite charges set in shallow drill holes to determine the subsurface structural picture by bouncing induced vibrations off the deep layers of rocks. Geologists studied the rock outcrops, re-examined old well data, and generated new maps and cross sections to identify potential traps for oil and gas. Everyone was excited at the prospect of finding similar large oil fields throughout central Utah, including local citizens, Sevier and Sanpete county commissioners, Utah legislators, geologists and oil companies, speculators, and the news media. The Covenant discovery even made the cover of the American Association of Petroleum Geologists (AAPG) monthly news magazine, the Explorer, which is distributed to over 30,000 geologists worldwide.

Over the years, Covenant field has met all expectations. The field has produced nearly 27 million barrels of oil! Thirty-four production wells were drilled in the field, and although Covenant now produces more water than oil (a natural occurrence as oil fields mature), the field still flows over 3,400 BOPD. Oddly, no gas, usually associated with oil, has ever been produced from Covenant

Oil and water production, as well as number of wells, from Covenant field, 2004-2018. Source: Utah Division of Oil, Gas and Mining.

Unfortunately, the search for another Covenant field in the central Utah thrust belt has been unsuccessful with about 30 wells drilled since 2004 attempting to penetrate similar traps of oil; one small field, Providence, about 15 miles northeast of Covenant in Sanpete County, was discovered in 2008 and has produced only about 445,000 barrels of oil from one well. There are several reasons for these disappointing results: (1) the structural targets (traps) were different or more complex than predicted (shallow, contorted layers of Jurassic-age mudstone and evaporite [anhydrite, gypsum, and salt] in the region often make interpretation of the deeper rock configuration extremely difficult), (2) additional potential reservoir rocks outside of the producing formations had low porosity and permeability and thus were unable to store or flow oil, (3) oil migrated from organic-rich source rocks prior to the formation of most traps, and (4) geologists still do not fully understand the petroleum system of the region. The lack of drilling success, the collapse of oil prices in late 2014, and the proliferation of lower risk yet economically viable shale-oil plays (e.g., the Permian Basin of West Texas) has halted almost all exploration in the central Utah thrust belt.

On the positive side, geologists have learned a great deal since the discovery of Covenant field that can be used in future exploration efforts. Initially, oil production was interpreted to be from the Early Jurassic-age (about 190 to 183 million years ago [Ma]) Navajo Sandstone that was deposited in a great sand “sea” or erg, similar to the Sahara (see Survey Notes, v. 48, no. 2). New outcrop work, regional well correlations, and age dating were used to determine that the upper section of what was thought to be Navajo is actually the Middle Jurassic-age (173 to 170 Ma) Temple Cap Formation. The Temple Cap was deposited as coastal dunes (White Throne Member) and associated tidal flats (Sinawava Member) analogous to the modern coast of Namibia of southwestern Africa. The Temple Cap Formation is separated from the underlying Navajo Sandstone by the J-1 unconformity—a time gap of over 10 million years (see Survey Notes, v. 50, no. 1). These units are best observed in outcrops in Zion National Park. To date, Covenant is the only field in Utah that produces from the Temple Cap Formation. Both the Navajo Sandstone and White Throne Member of the Temple Cap Formation have excellent reservoir properties (porosity and permeability) in the field that result in high oil storage and flow capacity. The producing wells in Covenant field are about equally divided between the Navajo and White Throne. Impermeable mudstone beds in the overlying Sinawava Member and anhydrite, gypsum, salt (halite), shale, and mudstone in the Arapien Formation (also Middle Jurassic in age) provide the seals for the underlying reservoir rocks.

Jurassic-age Navajo Sandstone and Temple Cap Formation (view west) near the east gate of Zion National Park. Photo by Doug Sprinkel.

The interpretation of the Covenant trap also changed since the field was discovered. The original drilling objective, a “rollover” anticline, was thought to have formed on a typical east-directed thrust splay off a larger, deeper thrust fault (a low-angle fault where older rocks have been displaced by compressional forces over younger rocks). However, when Wolverine drilled an injection well into the Navajo Sandstone to dispose produced water from the field, they encountered the Navajo only once instead of twice as was expected based on the presence of the thrust splay as shown on their cross section. This discovery indicated that the producing anticline was actually created by a west-directed back thrust, a type of structural feature along the regional-scale Sanpete–Sevier Valley anticline and extensively mapped by Utah Geological Survey geologists and others. Furthermore, the back thrust likely developed after an initial anticlinal “paleotrap” and in the process of reconfiguring the structure, any gas associated with the oil leaked to the surface as seeps or migrated to other potential reservoir rocks where it remains to be discovered.

Structural cross sections through Covenant oil field. A. Initial interpretation following the discovery showing a “rollover” anticlinal trap created by a splay thrust off a large, deeper thrust fault. B. Reinterpretation after a produced-water disposal well was drilled showing the anticlinal trap created by a back thrust. Modified from Wolverine Gas & Oil Corporation.

The 2004 discovery of Covenant field proved that the central Utah thrust belt has all the right components for major accumulations of oil: (1) nearby organic-rich source rocks, (2) large but complex traps, (3) high-quality reservoir rocks sealed by overlying impermeable beds, and (4) a complex yet ultimately favorable oil migration history. Although much has been learned over the past 15 years based on the Covenant discovery, it will require higher oil prices, companies and investors willing to take big risks, continued good science, and a bit of luck to find another large field in the central Utah thrust belt. Otherwise, Covenant may remain a “one-field wonder” for years to come.

Glad You Asked: Needing a Great Resource for Teaching Your Students About Utah Fossils?


Needing A Great Resource for Teaching Your Students About Utah Fossils?

by Marshall Robinson

The UGS has many resources and tools for teachers including teaching kits, geologic guides, geology-related videos, and maps. Additionally, our interactive web maps are a great resource to start with as they provide a wide variety of geologic information in one spot that teachers from across the world can access. Over the past several years, the UGS has created these user-friendly, informationrich interactive maps to enable map users to explore and understand geology in a more immersive way.

Screenshot of the Geologic Map Portal showing an oblique view of Mt. Timpanogos and Provo Canyon from the south. The 3-dimensional base map allows the user to see the relationship between the landscape and geologic formations (colored polygons), faults (heavy black lines), and ancient shorelines of Lake Bonneville (blue lines).

The Geologic Map Portal was the first interactive map created for the UGS website, and it displays a collection of over 800 of Utah’s best geologic maps. Every geologic map is available for download in various formats, with some of the more recent maps (and all 30′ x 60′ quadrangles) available in a GIS (geographic information system) format. Each colored polygon (which represents a closely related group of rocks, i.e., formations) is clickable, which opens a pop-up showing detailed rock unit descriptions. An improvement to this application came a couple years ago when the 2-dimensional base map was converted to a more true-to-life 3-dimensional base map. This improvement allows the user to tilt and rotate the map to see the rock units in a way that helps them better understand the relationship between geology and landscape. Elementary school teachers and college professors alike can take advantage of this new visual aid to help them teach their students geology in both the classroom and field. Although experiencing geology in person and in the field is probably the best way to understand difficult geologic concepts, our interactive map can certainly add to the experience as it allows you to see the geology of any given location in Utah whenever you want.

In the past 10 years, the UGS has built over 20 interactive maps focused on many aspects of geology. Some of the more useful applications for teachers are centered around popular geology, geologic hazards, and energy and mineral resources. Every interactive map we have created is on the UGS Interactive Maps web page, but a brief summary of some of our more helpful interactive maps follows.

Screenshot of the GeoSights interactive map. Here, people can find many of Utah’s very unique geologic wonders.

Popular Geology

(click on “Popular Geology” filter on Interactive Maps web page):

This option is for those looking for more “general information” interactive maps. These maps give detailed information about rockhounding, fossil sites, pretty landscaping rocks, and fascinating geologic sites throughout the state (called GeoSights). These interactive maps are a great resource for finding and understanding some of Utah’s more fun geologic resources.

Screenshot of the Utah Quaternary Fault & Fold Database interactive map. The different line colors correspond to how recently the fault last moved and ruptured the ground surface, generating a large earthquake.

Geologic Hazards

(click on “Hazards” filter on Interactive Maps web page):

The Utah Quaternary Fault & Fold Database map shows all of Utah’s active faults. On this interactive map one can find if their home or prospective home is near a fault line. The lines on this map represent faults generally considered to be likely sources of large earthquakes (about magnitude 6.5 or greater). Additionally, a more all-inclusive hazards application is being developed that will display all available geologic hazard data in one interactive map.

Though it is not a true interactive map, we also provide an interactive “story map” of Large Earthquakes on the Wasatch Fault. This teaching tool is great for anyone looking to gain a general understanding of Utah’s most hazardous fault system as you can scroll through and learn when large earthquakes have occurred on the Wasatch fault over time in addition to how we have gathered this information.

Energy Resources

(click on “Energy Resources” filter on Interactive Maps web page):

Many teachers may not know that the UGS houses rock core samples and cuttings from thousands of oil and gas wells in a large warehouse building known as the Utah Core Research Center. We created an interactive map to display all of the data from each well in a user-friendly format. These data include information about well location and depth, rock type, and, in some cases, high-resolution photos of the core. Another useful resource map is about Utah’s mining and industrial resources. This new interactive map shows where all of Utah’s mining districts are located as well as where limestone, gypsum, dolomite, and bentonite resource potential is best in Utah. Seeing the location of these mineral resources is an important step in learning the geologic history of Utah because specific minerals are found in specific geologic environments (for more information on this topic, see the “Glad You Asked/Teacher’s Corner” article in the September 2018 issue of Survey Notes).

The UGS website has interactive maps for a broad audience. Everyone from amateur rock-hounders to teachers to researchers and consultants will find valuable data in our interactive maps. Other UGS interactive maps cover topics ranging from geothermal and wetlands data to groundwater and mineral resources. We continue to work hard on providing the most up-to-date and accurate data in the most user-friendly way possible.

GeoSights: Crystal Peak, Millard County, Utah


GeoSights: Crystal Peak, Millard County, Utah

by Mackenzie Cope

Traveling through the seemingly endless Great Basin Desert in western Utah, an unusual sight suddenly appears as you pass yet another mountain range. As if teleported from another dimension, the other side of the expansive valley holds a bright white, glowing mountain nestled between brown, red, and gray cliffs. How does such a striking, isolated dome form in the middle of the desert? Clues to the geologic story of Crystal Peak come from the volcanic rocks of the Tunnel Spring Tuff, major tectonic events of the region, and the cavernous structures called tafoni that cover the mountain from top to bottom.

View to the east of Crystal Peak. The glowing quality of the peak is due to the high concentration of quartz crystals in the Tunnel Spring Tuff. The peak is more resistant to erosion than the surrounding areas making it prominent.

Tunnel Spring Tuff

The white, sparkly rock of Crystal Peak is called the Tunnel Spring Tuff. It is a rhyolitic ash-flow tuff made of pyroclastic debris from an explosive volcanic eruption. The composition of the tuff is a mixture of ash, pumice, glass shards, minerals, and abundant rock fragments of limestone, sandstone, shale, and dolomite. The white color of the rock comes from its concentration of ash and pumice. The mountain’s name derives from the abundance of crystals mainly quartz, sanidine, plagioclase, and minor biotite— that cause the mountain to sparkle. The quartz crystals in the Tunnel Spring Tuff have well formed points on both ends— referred to as double terminated—making this formation easily identifiable. These 3-millimeter-long (1/8 inch) crystals are best seen with a hand lens or magnifying glass and are clear or smoky gray in color.

Geologic History

The geologic story of Crystal Peak starts with the erosion of Paleozoic-age sedimentary rock layers called the Pogonip Group. The formations in the Pogonip Group consist of limestone, sandstone, shale, and dolomite. They range from 382 to 485 million years old and collectively are about 1,000 meters (3,300 feet) thick. These formations are the source of the sedimentary rock fragments in the Tunnel Spring Tuff; the fragments are known as xenoliths, literally “foreign stone,” from the Greek “xenos” (foreign) and “lithos” (stone). The Pogonip Group was eroded when a river system carved a deep stream valley over a span of millions of years (block 1).

During the Oligocene Epoch, about 33 million years ago, an explosive volcanic eruption threw large amounts of ash, pumice, and rock into the air that rained down covering large areas of land. The volcanic ash and other material settled in topographic low areas like the stream valley eroded into the Pogonip Group, eventually forming the Tunnel Spring Tuff (block 2). The rock fragments in the Tunnel Spring Tuff are likely derived from the caldera walls from which the volcano erupted.

After the deposition of the tuff, north-south trending normal faults, associated with Basin and Range extension, cut the landscape. As the crust was extending, uplifted fault blocks (horsts) and down-dropped fault blocks (grabens) broke apart the former Pogonip stream valley now filled with the Tunnel Spring Tuff (block 3). Sections of the former stream valley were uplifted while neighboring areas were dropped down.

The formation of Crystal Peak. (1) A stream valley is carved into the sedimentary rocks of the Pogonip Group. (2) A volcanic eruption fills the stream valley with ash, pumice, and Pogonip Group rock fragments as a rhyolitic ash-flow tuff where it lithifies into the Tunnel Spring Tuff. (3) Basin and Range extension causes normal faulting in the Tunnel Spring Tuff and Pogonip Group. (4) A ridge of Tunnel Spring Tuff forms while the sedimentary rocks of the Pogonip Group are eroded. (5) The slightly-welded rhyolitic ash-flow tuff erodes more slowly until only a single dome-like peak—Crystal Peak—is left. (Modified from Bushman, A.V., 1973, Pre-Needles Range Silicic Volcanism, Tunnel Spring Tuff [Oligocene], West-Central Utah)

Over time, erosion started to affect the horsts, filling the grabens with sediment. The Pogonip Group, made up of softer sedimentary rocks, eroded more quickly than the resistant ash-flow tuff. A ridge of Tunnel Spring Tuff thus formed, while the adjacent Pogonip Group rocks eroded down to a lower elevation. An inverted valley was created whereby the original topographic lows became the topographic highs and vice versa (block 4). Today, most of the Tunnel Spring Tuff has been eroded away and only occurs in a handful of locations in southwestern Utah. Crystal Peak is the thickest remaining section of the Tunnel Spring Tuff (block 5).


Tafoni (also called honeycombs, alveoli, and stonelace) cover the surface of Crystal Peak. They are characterized by clusters of holes and recesses formed from cavernous weathering. The tafoni on Crystal Peak completely cover the steep sides, creating a “swiss cheese” texture on the surface. They are actively forming today as the Tunnel Spring Tuff continues to weather and erode.

Tafoni vary in size, with some of the largest cavities being over 2 meters (6 feet) wide. The tafoni cover most of the steep sides on Crystal Peak.

Tafoni form in a variety of environments and rock types but are most common in salt-rich desert environments and coastal areas. The composition of the rock plays the most important role in tafoni creation. The Tunnel Spring Tuff is poorly welded and thus somewhat porous and permeable. As weathering occurs, rainwater containing carbonic acid (H2CO3) infiltrates the tuff and travels through the pore spaces.

The absorbed water moves via capillary action. In this case, it means using the walls of the small spaces to propel the water horizontally through the rock body. The acidic water in the pore space dissolves limestone and dolomite rock fragments as it moves through the rock. The water eventually evaporates, leaving calcite (CaCO3) behind.

This dissolution starts a process called salt weathering. Although usually facilitated by the minerals gypsum or halite, the salt weathering that initiates tafoni formation at Crystal Peak is driven by the crystallization of calcite (CaCO3) precipitated from water. Calcite crystallization can generate a pressure of 10 atmospheres, a pressure strong enough to break rock grains and walls of the pore spaces, expanding the open area in the rock. The process feeds on itself as larger tafoni help regulate humidity and temperature, promoting more crystallization and subsequent weathering. The pore spaces grow into cavities and continue to increase in size.

Research shows that the cavities are spherical until they reach about 20 centimeters (8 inches) in diameter. The width then increases faster than the height and depth and they become elongated cavities. The average width of the tafoni at Crystal Peak is 2 meters (6 feet) but varies considerably. The spacing of the tafoni is a mystery as they do not follow any significant pattern or condition for their placement on steep rock faces.

Researchers will doubtless learn more about Crystal Peak and its tafoni, but time is not unlimited. In another million years, Crystal Peak, the Tunnel Spring Tuff, and the cavelike tafoni may be completely eroded away and replaced with a new geologic mystery, erasing the last piece of evidence for the ancient stream valley and violent volcanic events that occurred in this remote western desert of Utah.

How to Get There:

The roads leading out to Crystal Peak are well-maintained gravel and dirt. A four-wheel-drive vehicle is not necessary but may reduce travel time. Travel is  not recommended in winter or in bad weather conditions. There are no parking areas or facilities at Crystal Peak so use caution when parking on the shoulder and be prepared with plenty of water, food, sun protection, and fuel.

GPS Coordinates: 38.7965° N, 113.5962° W

From Delta:

  • Head west on Main Street/U.S. Route 6/50 for about 5 miles.
  • Turn left onto Utah State Route 257 and travel south for 47 miles.
  • Turn right at Black Rock Road/Crystal Peak Road and continue for 3 miles.
  • Keep left, then stay on the main road for 9.5 miles.
  • At the fork, go left and continue straight for 5.5 miles.
  • At the fork, go right and stay on the main road for 17 miles to arrive at Crystal Peak.

From Milford:

  • Travel north on Main Street/Utah State Route 257 for 22 miles.
  • Turn left at Black Rock Road/Crystal Peak Road and continue for 3 miles.
  • Keep left, then stay on the main road for 9.5 miles.
  • At the fork, go left and continue straight for 5.5 miles.
  • At the fork, go right and stay on the main road for 17 miles to arrive at Crystal Peak.

Powell’s 1869 Journey Down the Green and Colorado Rivers


Major John Wesley Powell’s 1869 Journey Down the Green and Colorado Rivers of Utah

by Thomas C. Chidsey, Jr.

Past these towering monuments, past these mounded billows of orange sandstone, past these oak-set glens, past these fern-decked alcoves, past these mural curves, we glide hour after hour, stopping now and then, as our attention is arrested by some new wonder…

These words by Major John Wesley Powell, August 3, 1869, describe the scene as he and his comrades floated along the Colorado River in what is now southern Utah. Anyone who now travels his same route or visits the various national parks and surrounding regions likewise has their “attention arrested by some new wonder!” Powell is best known for his historic journey down the Colorado River through the depths of the Grand Canyon 150 years ago. However, of that 1,000-mile journey, about 570 miles (roughly 58 percent) were down the Green and Colorado Rivers through Utah. Most of the spectacular areas and landmarks along the way that are so familiar to generations of Utah citizens and visitors were named by Powell and his party.

The purpose of Powell’s 1869 expedition was to survey the geology, geography, and water resource potential for settling the region, and document ethnography and natural history of the canyons of the Green and Colorado Rivers. Though his expedition was “scientific,” Powell was well aware that he was competing with other government surveys for funds, and that adventures such as his river journey drew much public interest and support. The expedition was made possible, in part, by the construction of the Transcontinental Railroad (Union Pacific) through Wyoming, which delivered four modified, round-bottomed Whitehall rowboats that were built in Chicago: Maid of the Cañon, Kitty Clyde’s Sister, No Name, and the Emma Dean named after Powell’s wife and specially rigged for him to command during the trip to accommodate him having one arm.

Powell and his party of nine others departed Green River Station (now the town of Green River, Wyoming) on May 24, 1869, two weeks after the Golden Spike had been laid at Promontory, Utah, completing the Transcontinental Railroad. The boats were laden with supplies to last 10 months and they took several scientific instruments including sextants, chronometers, thermometers, compasses, and barometers (to measure the altitude of the river and surrounding terrain). They would endure numerous hardships along the way including negotiating hundreds of rapids, the loss of two boats with much of their supplies and scientific instruments, surviving near drownings, food spoilage and near starvation, and even outrunning a flash flood. One member of the crew would depart the expedition near Vernal, Utah, having had enough adventure, and three others left near the journey’s end thinking an impending rapid too dangerous—they were never seen again.


Traveling uneventfully down 60 miles on the Green River, most of which is now Flaming Gorge Reservoir, Powell and his party reached the Utah Territory on May 26.

The river is running to the south; the mountains have an easterly and westerly trend directly athwart its course, yet it glides on in a quiet way as if it thought a mountain range no formidable obstruction. It enters the range by a flaring, brilliant red gorge, that may be seen from the north a score of miles away. The great mass of the mountain ridge through which the gorge is cut is composed of bright vermilion rocks; but they are surmounted by broad bands of mottled buff and gray, and these bands come down with a gentle curve to the water’s edge on the nearer slope of the mountain. This is the head of the first of the canyons we are about to explore—an introductory one to a series made by the river through this range. We name it Flaming Gorge [1 on map].

Major John Wesley Powell,
May 26, 1869

The mountain range Powell describes is the east-west-trending Uinta Mountains. The rocks at the entrance to Flaming Gorge that so much impressed Powell are the north-dipping, slope-forming, vermilion-colored Triassic (251 to 200 million years ago [Ma]) Moenkopi and Chinle Formations overlain by the buff-gray Triassic-Jurassic (200 to 183 Ma) Nugget Sandstone and the Jurassic (169 to 155 Ma) Carmel, Entrada, and Stump Formations.


After crossing the Uinta fault, the Green River follows a generally easterly course through Precambrian (800 to 770 Ma) rocks exposed spectacularly in Red Canyon (now popular for river rafting below the Flaming Gorge Dam) and then Browns Park. Eventually (after about 54 miles), the river enters Colorado through the Gates of the Lodore and turns south into a region that is now part of Dinosaur National Monument where Powell lost the No Name, much of their supplies, and scientific instruments in a rapid they appropriately named Disaster Falls. After the river course changes to the west, it reenters Utah.

The Green is greatly increased by the Yampa [River], and we now have a much larger river. All this volume of water, confined, as it is, in a narrow channel and rushing with great velocity, is set eddying and spinning in whirlpools by projecting rocks and short curves, and the waters waltz their way through the canyon, making their own rippling, rushing, roaring music…One, two, three, four miles we go, rearing and plunging with the waves, until we wheel to the right into a beautiful park and land on an island, where we go into camp…e broad, deep river meanders through the park, interrupted by many wooded islands; so I name it Island Park, and decide to call the canyon above, Whirlpool Canyon [2 on map].

Major John Wesley Powell,
June 21 and 22, 1869

The oldest formation exposed in Whirlpool Canyon is the Precambrian (900 Ma) Uinta Mountain Group which is overlain by Cambrian (540 Ma) Lodore Sandstone and Mississippian and Permian (340 to 275 Ma) strata, all relatively resistant to erosion and deeply incised by the river. When Powell exited the canyon and entered the open area he named Island Park, the expedition had crossed the northeast-southwest-trending Island Park fault. This major fault displaces softer, less-resistant Triassic and Jurassic formations on the west side, including the Moenkopi and Chinle Formations exposed in Flaming Gorge, against the Pennsylvanian-Permian (280 to 275 Ma) Weber Sandstone on the east side.


At the lower end of the park, the river turns again to the southeast and cuts into the mountain to its center and then makes a detour to the southwest, splitting the mountain ridge for a distance of six miles nearly to its foot, and then turns out of it to the left. All this we can see where we stand on the summit of Mount Hawkins, and so we name the gorge below, Split Mountain Canyon [3 on map].

Major John Wesley Powell,
June 24, 1869

For the description of Split Mountain Canyon, see the “Glad You Asked” article in this issue.


After passing through Split Mountain, the Green River follows a gentle, south-southwesterly meandering course through the Eocene (55 to 43 Ma) Uinta and Green River Formations in the Uinta Basin. Powell passed many major oil and gas fields that would not be drilled for many years. After about 90 miles the river again downcuts into older rocks which created another major and perilous canyon for the Powell expedition.

After dinner we pass through a region of the wildest desolation. The canyon is very tortuous, the river very rapid, and many lateral canyons enter on either side. These usually have their branches, so that the region is cut into a wilderness of gray and brown cliffs. In several places these lateral canyons are separated from one another only by narrow walls, often hundreds of feet high—so narrow in places that where softer rocks are found below they have crumbled away … Piles of broken rock lie against these walls; crags and tower-shaped peaks are seen everywhere, and away above them, long lines of broken cliffs; and above and beyond the cliffs are pine forests, of which we obtain occasional glimpses as we look up through a vista of rocks. The walls are almost without vegetation; a few dwarf bushes are seen here and there clinging to the rocks, and cedars grow from the crevices—not like the cedars of a land refreshed with rains, great cones bedecked with spray, but ugly clumps, like war clubs beset with spines. We are minded to call this the Canyon of Desolation [4 on map].

Major John Wesley Powell,
July 8, 1869

Desolation Canyon exposes rocks of the Eocene (55 to 45 Ma) Green River and Paleocene-Eocene (about 60 to 55 Ma) Wasatch Formations which, in this area, were deposited as shallow-water muds, shoreline river deltas, and alluvial plains along or near the southern parts of an ancient lake called Lake Uinta. The Green River and Wasatch Formations are major producers of oil and gas in the Uinta Basin.

Again, the large rapids in Desolation Canyon posed major difficulties for Powell and his party. Most of the rapids that they encountered here and along the entire journey formed adjacent to major side canyons when large flash floods deposited boulders in the rivers. These boulders dammed up the rivers (a calm before the storm!) with the rapid created where the water flows over the “dam.”


The Green River continues to follow a southerly course into Gray Canyon, cutting down through the coal-bearing formations of the Cretaceous (84 to 67 Ma) Mesaverde Group until it exits the canyon at the Book Cliffs near the town of Green River, Utah. From there the river continues south, eroding deeper into older strata that create the classic Colorado Plateau canyon country of southern Utah.

…with quiet water, still compelled to row in order to make fair progress. The canyon is yet very tortuous. About six miles below noon camp we go around a great bend to the right, five miles in length, and come back to a point within a quarter of a mile of where we started…There is an exquisite charm in our ride to-day down this beautiful canyon. It gradually grows deeper with every mile of travel; the walls are symmetrically curved and grandly arched, of a beautiful color, and reflected in the quiet waters in many places so as almost to deceive the eye and suggest to the beholder the thought that he is looking into profound depths. We are all in fine spirits and feel very gay, and the badinage of the men is echoed from wall to wall. Now and then we whistle or shout or discharge a pistol, to listen to the reverberations among the cliffs… we name this Labyrinth Canyon
[5 on map].

Major John Wesley Powell,
July 15, 1869

The Green River meanders through Labyrinth Canyon exposing spectacular sandstone cliffs of the Triassic-Jurassic Glen Canyon Group (see cover image). These strata were deposited in great “seas” of wind-blown sand like those of the modern Sahara, separated by a period when the climate changed and westerly flowing, sand-laden braided streams dominated the region.

The Colorado Plateau began rising during the Miocene Epoch (23 Ma). At that time the ancestral Green River and its tributaries flowed through meandering channels in wide valleys on easily eroded rocks such as the now-removed Cretaceous Mancos Shale, still exposed just south of the Book Cliffs. Once these river channels were established, they later became superimposed and entrenched into resistant rocks, such as the sandstones of the Glen Canyon Group, as the landscape changed from one of deposition to one of massive erosion where thousands of feet of sedimentary rocks have been removed.


From Labyrinth Canyon the river continues a similar meandering course, cutting into even older rocks, and enters what is now Canyonlands National Park.

The stream is still quiet, and we glide along through a strange, weird, grand region. The landscape everywhere, away from the river, is of rock—cliffs of rock, tables of rock, plateaus of rock, terraces of rock, crags of rock—ten thousand strangely carved forms; rocks everywhere, and no vegetation, no soil, no sand. In long, gentle curves the river winds about these rocks… rapid running brings us to the junction of the Grand [now the Colorado River] and Green, the foot of Stillwater Canyon, as we have named it [6 on map]. These streams unite in solemn depths, more than 1,200 feet below the general surface of the country.

Major John Wesley Powell,
July 17, 1869

The rocks Powell described from Stillwater Canyon consist of Triassic Moenkopi and Chinle Formations that he first observed in Flaming Gorge, and the Permian (280 to 275 Ma) Cutler Group. The chocolate- to brown-red-colored Moenkopi was deposited in a tidal-flat environment, as attested by its abundance of ripple marks on thin slabs of rocks, and the Chinle, famous for its petrified wood, uranium, and beautiful multicolored mudstone and shale, represents a river floodplain. The Permian Cutler Group consists of the red-brown floodplain deposits of the Organ Rock Formation at river level capped by prominent cliffs of the White Rim Sandstone which represents ancient coastal dunes.

Large uplifts and basins developed in the Colorado Plateau during the Laramide orogeny (mountain-building event) between the latest Cretaceous (about 70 Ma) and the Eocene (about 34 Ma). Canyonlands National Park and the surrounding region is on the northern end of the broad Laramide-age Monument uplift, which is responsible for exposing the impressive stratigraphic section of older rocks carved into by both the Green and Colorado Rivers in southern Utah.


Once past the confluence of the two great rivers, the Colorado River flows in a southwesterly direction descending through one of the wildest series of rapids in Utah until it reaches Lake Powell 23 miles downstream.

We come at once to difficult rapids and falls, that in many places are more abrupt than in any of the canyons through which we have passed, and we decide to name this Cataract Canyon [7 on map].

Major John Wesley Powell,
July 23, 1869

The geology along Cataract Canyon is unique and the Colorado River likely has been a factor in the canyon’s structural development. The river follows a relatively straight course down the axis of a large anticline (upwarp) called the Meander anticline. Open-marine limestone beds of the Pennsylvanian (305 to 300 Ma) Honaker Trail Formation dip to the southeast and northwest, respectively, on each side of the river topped by progressively younger Permian formations. The Honaker Trail is underlain in the subsurface by the older Pennsylvanian Paradox Formation that contains evaporite rocks (gypsum and salt) which were deposited in a restricted marine environment. When under pressure, evaporites can flow like toothpaste being squeezed from a tube and push up the overlying rocks or even reach the surface (Powell recognized one such location and named it Gypsum Canyon, a side canyon to Cataract). The Meander anticline was formed this way and is underlain by a mass of mobilized gypsum and salt. As the Colorado River eroded the overlying section of rocks, the pressure on the evaporites below was reduced allowing them to push up even more. The evaporites withdrew from under the rocks adjacent to the canyon which caused collapse, faulting, and slumping towards the river. This process is still active today and contributes to huge rapids like Satan’s Gut and Little Niagara. This area is known as The Grabens in Canyonlands National Park.


Upon leaving Cataract Canyon, the Colorado River turns westerly and enters the upper reaches of Lake Powell, named, of course, for the famous explorer. After passing the Dirty Devil River, so-called by one of Powell’s men because of its muddy water and foul smell, the rocks become younger in age (Permian, Triassic, and finally Jurassic) to the south.

On the walls, and back many miles into the country, numbers of monument-shaped buttes are observed. So we have a curious ensemble of wonderful features—carved walls, royal arches, glens, alcove gulches, mounds, and monuments. From which of these features shall we select a name? We decide to call it Glen Canyon [8 on map].

Major John Wesley Powell,
August 3, 1869

The features Powell used to name Glen Canyon are most prominently displayed in the Jurassic (190 Ma) Navajo Sandstone, famous for its classic cross-bedding and representing ancient dunes of windblown sand.

Glen Canyon and the canyons in the surrounding region, including those that Powell explored, formed within the past 5 million years by vigorous downcutting of the Colorado River and its tributaries, exposing more than 8,000 feet of bedrock that spans a period of about 300 million years. Powell no doubt would be shocked and amazed to see the reservoir that bears his name. All outcrops at river level and in many of the side canyons that Powell explored are covered by water, in many places hundreds of feet deep. Fortunately, the lake level creates an ideal horizontal datum along which large folds (anticlines and synclines) bring most of those outcrops, ranging in age from Triassic to Jurassic in the heart of Glen Canyon, to places where they can be observed from the comfort of a boat.

The 710-foot-high Glen Canyon Dam, located just south of the Utah border near Page, Arizona, was authorized by Congress in 1956 to provide water storage in the upper Colorado River basin, and construction began that same year. Lake Powell is the second largest reservoir in the United States (Lake Mead in Nevada and Arizona is the largest). The lake is 186 miles long, and with 96 major side canyons, it has more than 1,960 miles of shoreline—more than twice the length of the California coastline. The surface area of Lake Powell is 266 square miles and it is 560 feet deep at the dam. Lake Powell holds up to 27 million acre-feet of water, enough to cover the state of Ohio with one foot of water! The hot arid climate causes an average annual evaporation of 2.6 percent of the lake’s volume. Siltation in the lake averages 37,000 acre-feet per year, brought in principally from the San Juan and Colorado Rivers. That is the equivalent of 6 million dump trucks of silt each year! Even at that rate, it will take 730 years to fill the lake with silt.

Although the most famous part of Major John Wesley Powell’s 1869 expedition was the journey of what Powell called “the Great Unknown” of the Grand Canyon, he first spent most of his time exploring the canyons of the Green and Colorado Rivers in Utah. This expedition represents an amazing feat by Powell and his team at that time. Before Powell left the Utah Territory and entered what is now Arizona, he wrote “…we reach[ed] a point which is historic.” Powell was referring to a point along the Colorado River known as El Vado de los Padres or Crossing of the Fathers, a ford (now under 400 feet of water in Padre Bay in Lake Powell) named for Fathers Dominguez and Escalante who discovered it during their 1776 expedition through the region. For those of us who boat around Lake Powell or Flaming Gorge Reservoir, or raft the Colorado or Green Rivers, we too reach points that are truly historic—first named and described by Powell and his colleagues 150 years ago. Major John Wesley Powell’s expedition was truly a major contribution to science and an incredible adventure that still inspires a spirit of curiosity and sense of wonderment today.

Powell quotes from Canyons of the Colorado, by J.W. Powell, 1895.

Tom Chidsey

is a senior scientist in the Energy & Minerals Program He has worked for the Utah Geological Survey for 30 years primarily conducting petroleum geologic studies. Tom is not only passionate about the geology of Utah, but history as well—especially the Civil War, World War I, and Major John Wesley Powell’s 1869 journey down the Green and Colorado Rivers He has retraced more than 800 miles of Powell’s route by raft and boat In addition, Tom was the senior author of the Utah Geological Association’s 2012 guide to the geology of Lake Powell.

Major John Wesley Powell: 1834–1902


Major John Wesley Powell: 1834–1902

by Mackenzie Cope

Major John Wesley Powell at his desk in Washington, D.C. circa 1890s (Smithsonian Institution Archives, Record Unit 7005, Box 187, Folder: 1; Record Unit 95, Box 18, Folder: 57)

Major John Wesley Powell at his desk in Washington, D.C. circa 1890s (Smithsonian Institution Archives, Record Unit 7005, Box 187, Folder: 1; Record Unit 95, Box 18, Folder: 57)

John Wesley Powell was born on March 24, 1834, in Mount Morris, New York, to Joseph Powell and Mary Dean. He grew up interested in history, literature, botany, zoology, and nature. Powell’s family moved to Ohio in 1838, Wisconsin in 1846, and settled in Illinois in 1851. In 1852, he became a teacher and attended college intermittently at the Illinois Institute, Illinois College, and Oberlin College, but never received a degree.

When the American Civil War started in 1861, Powell enlisted in the Union Army at age 27 as a topographer, cartographer, and military engineer and quickly advanced to a second lieutenant. He took leave on November 28, 1861, and married Emma Dean, the daughter of his mother’s half-brother, but returned to service soon after. On April 6, 1862, at the Battle of Shiloh in Tennessee, Powell was hit with a bullet in his right arm and field surgeons had to amputate it at the elbow. He became a recruiting officer back home in Illinois while recuperating from his injuries, but returned to active duty in 1863 and was promoted to the rank of major.

After the war, Powell taught natural sciences at Illinois Wesleyan University and later at Illinois State Normal University. In 1867, he became the curator of the Illinois Natural History Society Museum and organized a specimen-collecting expedition to Colorado where he climbed Pikes Peak and explored part of the Rocky Mountains.

In 1868 Powell organized the first of his great expeditions in the West to explore the Colorado River and its tributaries, which included his historic passage through the Grand Canyon. Funding for the trip, which started May 24 and ended August 30, 1869, came from the Illinois Natural History Society and Illinois Industrial University, with Powell’s promise of sharing data and specimens for study. Scientific instruments came from the Smithsonian Institution and the Chicago Academy of Science. Rations were provided by the U.S. Army with Congress’s authorization and transportation of the boats was courtesy of the Union Pacific railroad. The purpose of this expedition was to explore previously unmapped areas as well as study the geology and native flora and fauna.

Powell conducted a second expedition on the Colorado River from May 22, 1871, to September 7, 1872. This extended trip focused on collecting evidence and scientific data in the form of photographs, detailed maps, and observations for scientific publications. This expedition was funded by the U.S. Congress to obtain an accurate map of the Colorado River and surrounding areas. Powell wrote about his observations and data in his book, known today as Exploration of the Colorado River and Its Canyons, which is still printed and sold.

During his second Colorado River expedition, Powell employed Jacob Hamblin, a Mormon missionary from southern Utah, to help negotiate the safety of the trip. Hamblin had an excellent relationship with the Native Americans and Powell was able to study the Native American cultures of the West. From his ethnological work on his expeditions, he published Introduction to the Study of Indian Languages, with Words, Phrases, and Sentences to Be Collected in 1877 and Indian Linguistic Families of America, North of Mexico in 1891.

In 1879, Powell became the first director of the U.S. Bureau of Ethnology of the Smithsonian Institution and held the position until his death. Among the many organizations he worked for, one of Powell’s most respected achievements was serving as the second director of the U.S. Geological Survey (USGS) from 1881 to 1894, which he served concurrently with his other positions. He advocated strict water resource conservation based on his exploration of the American West’s river systems and geology. He published Report on the Lands of the Arid Regions of the United States in 1878 where one of his ideas was to draw state boundaries according to watershed areas. While he was the director of the USGS, Powell emphasized mapping and helped influence the call for nationwide 1:24,000-scale topographic maps. He resigned from the USGS in 1894 due to opposition to his water resource conservation efforts from western politicians.

Throughout his time as a geographer, geologist, and ethnologist, Powell helped organize and take part in many organizations other than the USGS. Some notable organizations include the Cosmos Club in Washington, the Anthropological Society of Washington, the Biological Society of Washington, the Geologic Society of Washington, the National Geographic Society, the Geological Society of America, and the American Association for the Advancement of Science.

Major John Wesley Powell died on September 23, 1902, at the age of 68, in his family’s vacation home in Maine and was buried in Arlington National Cemetery with full military honors. Today, Powell is remembered through landforms and natural features named after him (e.g., Mount Powell in the Uinta Mountains and Lake Powell in southern Utah) or by him (e.g., Glen Canyon in southern Utah) across the American West. He is honored for his contributions to geology, geography, ethnology, and the natural sciences as a whole.

A Google Earth© oblique view of Split Mountain and surrounding regions. Browns Park Gates of Lodore Canyon of Lodore Diamond Mountain Plateau Yampa Plateau Yampa River Echo Park Island Park Green River Green River Split Mountain Whirlpool Canyon A Google Earth oblique view

The Curious Case of the Green River in the Uinta Mountains


Glad You Asked: The Curious Case of the Green River in the Uinta Mountains

by Douglas A. Sprinkel

People often ask, Why does the Green River flow toward and through the Uinta Mountains? Or, Why does the Green River cut through the middle of Split Mountain when logically it should have flowed around it? Those questions also puzzled John Wesley Powell during the first-ever scientific exploration of the Green and Colorado Rivers in 1869 (see main article in this issue of Survey Notes).

During their month-long stay in the eastern Uinta Mountains, Powell and his companions explored the Green and Yampa Rivers as well as the side canyons and surrounding peaks. Some of our earliest state-of-the-art scientific measurements and descriptions of the geology were the result of that first expedition. Powell made a second trip down the Green and Colorado Rivers in 1871, as well as several pack trips into the territories of Colorado, Wyoming, and Utah. These overland traverses in 1868, 1869, 1874, and 1875 helped Powell formulate his understanding of the geology of the eastern Uinta Mountains.

During Powell’s first expedition, he noted that the Green River flows from its headwaters in the Wind River Mountains of Wyoming southward across a basin, toward the Uinta Mountains. However, at the foot of this mighty mountain range, instead of being deflected by the obstruction, the river flows directly into the range! This and other examples throughout the Uinta Mountains of where the Green River flows through obvious obstructions instead of around them sparked Powell’s imagination to explain such a peculiarity.

So how did the Green River achieve what seems to be an impossible route? At first Powell thought that the river simply followed established fissures within the range. However, Powell rejected that concept because “…very little examinations show that this explanation is unsatisfactory. The proof is abundant that the river cut its own channel; that the cañons are gorges of corrasion.” Powell concluded that the Green River had to have been running its course before the mountain range formed. Powell recognized that the Uinta Mountains are a large anticlinal fold that formed by uplift. He hypothesized that the uplift had to be slow enough for the Green River to cut into the rising fold without altering the river course. Thus, he surmised that the Green River cut its canyon as the range rose around it, and tributaries that fed into the Green River were agents of erosion that stripped the rock off the axis of the great arch. Had the uplift been rapid, the river would have been deflected to a new course that would take the Green River around the flanks of the Uinta Mountains. Powell coined the term “antecedent valley” for this hypothesis. He also coined the terms “consequent valley” for channels that form as a result of the existing topography and “superimposed valley” for channels that form on low-gradient surfaces over which the channel maintains its course even as the stream cuts down into pre-existing structures. The term “superimposed” has since been shortened to “superposed.” Powell also considered but rejected the notion that the Green River is a superposed stream.

Was Powell right? Work by geologists like Julian Sears in 1924 and Wilmot Bradley in 1936 provided evidence that a network of streams flowed away from the Uinta Mountains into the adjoining basins at the end of Uinta uplift during the Laramide orogeny (mountain-building event) 70 to 34 million years ago including where the Green River now flows toward the range. Sears also provided evidence that later faulting formed Browns Park and argued that the Green River was a superposed stream. However, work by Wallace Hansen from 1965 to 1986 provided the clearest picture of drainage reorganization and capture of the Green River. Stream or river capture (also called stream or river piracy) is the diversion of a stream from its current channel to the channel of the capturing stream, often causing the captured stream to reserve its flow. The lowering of the eastern Uinta Mountains by Neogene (20 million years ago to present) extensional faulting was the agent that caused the change in the eastern Uinta Mountain drainage system and the
ultimate capture of the Green River.

Powell and his companions reached Island Park on June 22, 1869, where they camped on one of the islands on the Green River. While there they explored the area noting topography and geology. They climbed the flank of Split Mountain to view the core of the mountain and the rapids within. Powell noted that the Green River entered the range through its north flank, then turned west down the axis of the fold before it turned south again to exit the mountain through its south flank.

Split Mountain is an anticline formed by uplift along the Island Park reverse fault zone, which is on the north limb of the fold. This faulting and folding are part of the general uplift of the Uinta Mountains. At the time of this deformation, the Mesozoic formations that typically overlie the Paleozoic formations were still present and involved in the folding. During a period of relative tectonic quiescence 34 to 25 million years ago, the flanks of the Uinta Mountains, including Split Mountain and the anticline, were buried by a thick blanket of sediments that became the Oligocene-age Bishop Conglomerate. The Bishop Conglomerate formed a low-gradient slope on which streams meandered. Before the Green River was captured and redirected toward the Uintas, it is thought that the Yampa River meandered across the landscape at nearly the present elevation of the Diamond Mountain and Yampa Plateaus (A). The relatively unobstructed Yampa River incised a canyon into the Bishop Conglomerate generally southwest to the Uinta Basin crossing what would become Echo Park, Whirlpool Canyon, Island Park, and Split Mountain. As downcutting continued, the canyon deepened and eventually cut into the emerging Split Mountain (B). The ancestral Yampa River probably took advantage of Laramide fractures on the flanks and crest of the anticline. The Yampa could have been captured by a stream that flowed down the anticlinal crest. Intriguing, beheaded valleys on nearby Blue Mountain, which could be either an ancestral channel of the Yampa, or of a major tributary, support this theory. Regardless, it seems clear to geologists that Split Mountain is a classic example of a superposed stream (C).

The final chapter in this story is the integration of the Green River into the Colorado River basin. Researchers now think that at Echo Park a tributary of the ancestral Yampa River occupied what is now Canyon of Lodore. In 2005, geologists Joel Pederson and Kevin Hadder argued that the tributary formed as Browns Park filled with sediment around the Gates of Lodore. This accumulation of sediment allowed the tributary to spill over and connect the drainage system in Browns Park with the Yampa River drainage and flow into the Uinta Basin, eventually joining the Colorado River below Green River, Utah. The Green River was now captured and redirected to flow toward the Uinta Mountains, through Flaming Gorge and Red Canyon, and down Browns Park to the spillpoint near the Gates of Lodore, completing the river system we see today (perhaps the river in the Uinta Basin should have been called the Yampa since the Yampa was there first!). So, Powell’s keen observations were amazingly astute, though evidence now shows a much more complicated story than he surmised.