SURVEY NOTES

Glad You Asked: What is Utah’s Largest Meteorite?

by Jim Davis


The Drum Mountains meteorite at the Smithsonian. Flat surface at top is where the meteorite was cut for sectioning. https://commons.wikimedia.org/wiki/File:Drum_Mountains_meteorite_in_Museum_of_Natural_History.jpg

The Drum Mountains meteorite at the Smithsonian. Flat surface at top is where the meteorite was cut for sectioning. https://commons.wikimedia.org/wiki/ File:Drum_Mountains_meteorite_in_Museum_of_Natural_History.jpg

Hands down, the Drum Mountains meteorite is the biggest meteorite from Utah. The iron-nickel meteorite is more than five times heavier than the collective weight of all 25 other official meteorites of Utah. At 1,164 pounds, it was at the time of its discovery the 9th largest meteorite to be recovered in the nation. The Drum Mountains meteorite has been held at the Smithsonian National Museum of Natural History since transfer from Topaz—the War Relocation Authority’s (WRA) Central Utah Project—in October of 1944, three weeks after its discovery.

Akio Ujihara, of West Los Angeles, and Yoshio Nishimoto, of Stockton, California, found the meteorite on or before September 24, 1944, while rockhounding for chalcedony for a lesson at the Topaz Lapidary School. They at once recognized that the rock was out of place, the size of a “potato sack” and the color of “burnt sienna.” Spectacular “thumbprints,” called regmaglypts, patterned its surface. Upon striking it with a hammer they knew it was pure metal by the sound. They detached chips off the meteorite and sent one to the Smithsonian with a sketch and description. 

The letter arrives on the desk of Edward P. Henderson, Associate Curator, Mineralogy and Petrology. Henderson was keen on finding out the location of the meteorite, if there were others nearby, if it was on public land, and if a crater was present. He requests a site visit from the U.S. Geological Survey (USGS) in Salt Lake City. Two weeks after the discovery, USGS geologist Arthur E. Granger is guided to the site. Henderson writes Granger, “. . . the sample is an iron meteorite, and if his [Nishimoto’s] measurements are correct, it is a large one, and therefore an important new find.” Granger reports, “The specimen was found in an area of low hills lying between the Drum Mountains and Little Drum Mountains” and “The country rock is entirely basic or basaltic lavas . . .” Granger finds no section corner markers, but concludes from “other observations” that the meteorite is in Township 15 South, Range 10 West, and “approximately” Section 29. This section is now geologically mapped as the Drum Mountains Rhyodacite, a dark-colored volcanic rock that spans the entirety of the broad saddle between the Drum and Little Drum Mountains. Section 29 is one square mile of federal public land. 

Inexplicably, Henderson’s official report published four years later gives the location as 5 miles east-northeast of Section 29, at 39° 30’ N, 112° 54’ W. By excluding seconds in the latitude and longitude coordinates, the area cannot be defined more precisely than around one square mile and places the meteorite on gently sloping stream-deposited (alluvial) sediments—more than 2 miles from bedrock. Yet in reinforcement of the geologist’s description, G.V. Morris, Evacuee Property Officer for the WRA at Topaz, recounts the journey with Granger, “. . . more or less extensive outcroppings of some black rock and the ground immediately thereabout more or less was covered by loose boulders.” Granger and Morris are the only officials to see the meteorite in its original setting. 

A meteorite this size might have produced a small crater, but none was found, perhaps erased by erosion. It lies in loose gravel, the bulk of it above ground. Mechanical weathering from wind-blown dust highlights the internal gridded crisscrossing fabric (called Widmanstätten) that stands in relief on the exterior. The buried portion is heavily weathered, corroded from continuous contact with soil moisture, the regmaglypts replaced by corrosion pits. Granger estimates it has sat in place for at least a century, but never sees the deteriorated underside. The weathering of the exposed section of the meteorite is minimal, a few hundredths of an inch, enough to remove any flow lines, or as Henderson writes to Ujihara, “. . . delicate flight markings . . . [which] differ a little from the big pits or depressions you noted (and said resembled Swiss cheese).” Oddly, when the story is finally released, newspapers quote Ujihara and omit the most descriptive word, “Swiss.” 

After Granger’s site visit Nishimoto and Ujihara muster friends and hire “local boys” to load the meteorite and truck it back to Topaz where it was placed on display for residents to view. Nishimoto then arranges for the meteorite to be transported by rail from Delta, Utah, to the Smithsonian in Washington, D.C. 

Topaz and the Drum Mountains/Little Drum Mountains

Topaz and the Drum Mountains/Little Drum Mountains

The Drum Mountains meteorite reinforced and contributed to future court rulings on meteorite ownership, such as they are property of the federal government if found on federal lands and subject to the 1906 Antiquities Act and that meteorites cannot be acquired through mining claims on federal land. Nishimoto staked a claim, or attempted to, on the site, likely at the suggestion of Morris, who mentions this particular to Henderson in a letter. This letter prompts Henderson to write the U.S. Secretary of the Department of the Interior, Harold L. Ickes, as to whether this would be an issue obtaining the specimen. The Assistant Secretary responds to Henderson that meteorites, like caverns, are “crystalline deposits marketable as curiosities,” and not patentable under mining laws. Regardless, no record of this claim seems to exist. 

Legally, meteorites are the property of the landowner. Henderson states in his letter to Granger, “If the meteorite is now on public land it is the property of the U.S. government. . . ” The meteorite’s transfer to the Smithsonian is swift, before a news release. Morris writes Henderson, “As far as I know the knowledge of the discovery has been kept within the bounds of the immediate center, and no publicity has been released except in the residence’s local paper [Topaz Times, October 11, 1944] which ran one story inviting the resident public here to inspect the specimen.” Nishimoto and Ujihara write Henderson, “For your information, both the University of Utah and the State Government of Utah have discovered with regret that the specimen has left the State and is now in your hands.” 

Henderson writes Morris and requests specifics on Nishimoto and Ujihara and the circumstances of their discovery. Ujihara writes to Henderson on letterhead from the Topaz Lapidary School, stating, “The pleasure is mine to communicate with a great scientist like Mr. Henderson through our finding which was merely an accident. As for myself, I lost my home, business, and major part of my savings due to the evacuation. But it is only infinitesimal compared to the millions of people of war zones. My only desire is that by this incident it may benefit to the scientific world and in some way it may open a way to establish a better world for the coming generations. . . ” 

The Arizona State University (Tempe) slice of the Drum Mountains meteorite is one of several sent to meteoritic institutions around the world. This slice has been polished and treated with a nitric acid solution to reveal the Widmanstätten pattern—a latticework of ribbon-like crystals of iron-nickel alloys (kamacite and taenite) that differ in color and luster due to varying concentrations of nickel. The sample weighs about 1.4 pounds. Photo by Devin L. Schrader/Center for Meteorite Studies/ ASU. Courtesy of the ASU Center for Meteorite Studies.

The Arizona State University (Tempe) slice of the Drum Mountains meteorite is one of several sent to meteoritic institutions around the world. This slice has been polished and treated with a nitric acid solution to reveal the Widmanstätten pattern—a latticework of ribbon-like crystals of iron-nickel alloys (kamacite and taenite) that differ in color and luster due to varying concentrations of nickel. The sample weighs about 1.4 pounds. Photo by Devin L. Schrader/Center for Meteorite Studies/ ASU. Courtesy of the ASU Center for Meteorite Studies.

Although under no obligation, the Smithsonian, using funds from an endowment for obtaining specimens, allots a finder’s fee to Ujihara and Nishimoto of $700 ($11,000 adjusted for inflation). Henderson writes Ickes, “We intend to reward these men for their discovery and have reason to believe they will accept it without hesitation.” Newspapers at the time had such titles as “Utah Meteorite Purchased,” though it was not a transaction because the meteorite was recovered on federal land; rather, it was an award for efforts and to more than cover moving and shipping expenses. 

The Smithsonian has a long history of meteorite collection and curation, scientific study, and collaboration with other meteoritical institutions and has been the traditional repository of meteorites found on federal land. The Smithsonian cut the Drum Mountains meteorite and sent samples, from largest to smallest, to Chicago, Moscow, Tempe, Ann Arbor, Calcutta, Madrid, and Harvard. Henderson also arranged, entirely unconventionally, for a slice to go to Ujihara and Nishimoto. Henderson writes Morris, “Most likely these men would appreciate a small polished slice as a memento of their discovery and I see no reason why we cannot present them each one.” In February 1950, a 6-ounce polished and etched slice was sent to Nishimoto in Stockton, California, and presumably one was sent to Ujihara’s address as well. Both discoverers of the Drum Mountains meteorite persisted in their zeal for rockhounding and lapidary, continuing in gem and Earth science clubs in California and appearing in magazines and articles for their techniques and notable finds. 

*Correspondence from Smithsonian Accession 168531. Misspellings in quotations are corrected.


Author’s Note, August 2022

Twenty-six meteorite finds in Utah are listed in the Meteoritical Society’s Meteoritical Bulletin Database. The odds of finding a meteorite are slim even if you see it fall. Most disintegrate before reaching the ground. For more information on meteorites and identification, please see the following resources.

Utah’s Clark Planetarium has a few meteorite experts. Contact them for local meteorite information.

Meteorite Information
Washington University in St. Louis

A Comprehensive Guide to Meteorite Identification
Aerolite Meteorites, Tucson, AZ

Meteorite Testing and Classifying Institutions
meteorite-identification.com

Meteorite or Meteorwrong?
UGS Survey Notes, 2008

What is Utah’s Largest Meteorite?
UGS Survey Notes, 2022

Have Meteorites or Meteorite Craters Been Found in Utah?
UGS Survey Notes, 2004

Do I Have a Meteorite?
Center for Meteorite Studies, Arizona State University


SURVEY NOTES

Glad You Asked! How does Plate Tectonics make for Great Skiing?

by Jim Davis


View from south side of Little Cottonwood Canyon looking northwest. Note skiers at ridge in foreground. The north side of the canyon exhibits the Little Cottonwood stock (~30 million years old), a magma intrusion, in contact with the Big Cottonwood Formation (~900 million years old). The stock intruded into the crust and cooled about 6 miles below the ground surface. The Big Cottonwood Formation is post-rifting in age, after the Wasatch hingeline was established, and is made up of sediment brought from rivers from eastern parts of the continent. Photo courtesy of Mark Milligan.

Great snow and great skiing and snowboarding are ultimately the result of plate tectonics. Plate tectonic activity, the relative movement of independent pieces of Earth’s exterior shell, involves the Earth’s plates migrating (changing their relative position), splitting apart (allowing new crust to form where magma wells up), and colliding with each other (destroying old crust in subduction zones). This activity creates the planet’s mountain ranges, volcanic chains, rift valleys, and ocean basins, ridges, and trenches. Snow conditions are a sum of topography, elevation, latitude, and distance to the ocean. These factors constrain climate and are shaped by a history of tectonics. Mountains govern the first two factors and all four factors govern snow—its quantity, quality, and duration.

TECTONIC HISTORY
Utah’s ski resorts are located along the Wasatch hingeline, a northeast to southwest band of mountains that arcs through central Utah. The hingeline’s origins stretch back nearly a billion years before the “Greatest Snow on Earth®.” Once formed, the hingeline perpetuated an east-west division in Utah through geologic time. The hingeline commenced with the break-up of the supercontinent Rodinia. The land rifted (split apart) along the hingeline, fragmenting the landmass and allowing oceanic crust to form in the gap. As the rift widened, the region west of the hingeline subsided for a long period of time, ocean waters encroached, and Utah was at the edge of the continent.
Hundreds of millions of years of quiescence followed, with tropical beaches, coral-filled seas, mud flats, lakes, broad river plains, and vast expanses of sand dunes. Stream networks drained much of the continent through Utah to the western ocean. Then plate tectonic activity resumed with the break-up of the supercontinent Pangea. The Farallon Plate began subducting beneath the continent, forming a convergent plate boundary. By Middle Jurassic time, around 170 million years ago, volcanism began in western Utah and 70 million years later mountain building ramped up from compression from the west. West of and at the Wasatch hingeline, the crust thickened and mountains formed from thrust sheets—large bodies of rock shoved eastward and folded. Intense volcanism ensued over much of the state. Throughout this mountain building time, Utah became steadily more distant from the western ocean.
After a time the remains of these mountains underwent the next and current stage of tectonics. Basin and Range extension is stretching and thinning Earth’s crust from the Wasatch hingeline to the Sierra Nevada. This deformation produced faulting that created long and repeating mountain ranges and valleys. Vertical movement on the Wasatch fault has resulted in the Wasatch Range abruptly rising thousands of feet above the adjacent valleys.
Yet how does this tectonic history make for favorable skiing and snowboarding? Here are a few factors that make skiing great in Utah, with focus on the central Wasatch Range and how plate tectonics fits in.

Structures such as faults, folds, and thrust sheets from prior mountain building episodes add attributes to the landscape and can be viewed from ski resorts, even under the snow cover of winter. The Hellgate Cliffs opposite the Snowbird resort exhibit a thrust fault where compressional forces from the west shoved rock eastward. The cliffs are a Mississippian-age limestone capped with older Mineral Fork Tillite and Tintic Quartzite. Photo courtesy of Mark Milligan.

SNOW COVER THROUGH THE SEASON
Tectonic plate migration has taken Utah from the equatorial latitudes and landed it squarely in the mid-latitudes. In this zone extratropical cyclones, weather systems some thousand miles across, pass intermittently from the Pacific Ocean to the Rocky Mountains, delivering blizzards. In a normal year, frontal storms through the winter and spring bring fresh snow to the mountains every week or two. Abundant spring storms can extend the ski season until early summer for some resorts. High elevation keeps temperatures cold and precipitation frozen late into the year.

ACCESS TO SLOPES 
The Wasatch fault has produced steep mountains without foothills. The physiography was beneficial for settlement and subsequent growth of the Wasatch Front urban corridor, a long, narrow strip of populated area where more than two million people now reside. The valleys have fertile soils and a long growing season with hot summers. The adjacent mountains provided timber, rangeland, metallic resources, and winter snowpack as a source of water for irrigation of valley crops. Consequently, an extensive metropolitan area is now located within minutes of the mountains. Nine premier ski resorts are within a one-hour drive of Salt Lake City.

TEMPERATURE RANGE
Skiers and snowboarders prefer that snow not melt or that temperatures are not too cold for comfort. Temperature is largely a function of latitude and elevation. The Cottonwood Canyon resorts, at 8,000 to 11,000 feet above sea level, have daily high temperatures in the winter months around 31°F, and daily lows around 9° to 14°F. Although the valleys are not much warmer in the winter than the mountains, springtime offers the opportunity to ski and bike on the same day.



HIGH-QUALITY SNOW
Utah’s interior position and the presence of numerous mountain ranges between the state and the ocean make for quality snow. Utah is about 600 miles or more from the ocean. Storms driven by the prevailing Westerlies from the Pacific Ocean must track perpendicular across the Sierra Nevada or Cascade Range, then across a washboard pattern of Basin and Range mountains. Along the way, these storms drop a significant amount of their original moisture as precipitation so that Pacific air masses arrive in Utah relatively dry. Along with bitterly cold temperatures aloft due to elevation and interior location, these relatively dry storms produce a variety of snowflakes—columns, plates, needles and dendrites—typically having a moderately low density. Alta snow density averages 7.8 percent December through January and 8.5 percent for the whole snow year.

ABUNDANT SNOW
Western Utah’s Great Salt Lake Desert receives as little as five inches of precipitation a year, whereas areas of the Wasatch Range average ten times as much precipitation, with hundreds of inches of winter snow. The upper Cottonwood Canyons are among the snowiest locations on Earth. Alta and Brighton have the 4th and 10th highest average annual snowfalls, respectively, in the United States. The steep relief of the Wasatch Range induces orographic lifting—air is forced to rise up and over the range. As air rises, it expands, cools, and its relative humidity increases leading to precipitation. Great Salt Lake, averaging 1,700 square miles and never freezing over, influences local weather. The lake is a product of Basin and Range tectonics and is the most prominent of the lakes of the Great Basin—the northern and internally drained area of the Basin and Range Province. Following the passage of a cold front, lake effect snow shower bands can stretch from the lake to the south, southeast, and east across the valleys and into the mountains, boosting snowfall.

VARYING TERRAIN AND BEAUTIFUL SCENERY
Latitude and elevation contributed to modest glacial growth in the Wasatch Range in the past. Recurring ice ages in the Quaternary Period, the last one peaking around 20,000 years ago, triggered alpine glaciation in Utah’s mountains. Glaciers begin growing in the shade of the highest summits, etching out bowl-like amphitheaters and sculpting pointed peaks and jagged ridges. The streams of ice then course downslope, carving U-shaped canyons and hanging valleys from tributary glaciers. The result is ski areas with variable topography—both abrupt and gentle—and vertical relief that locally exceeds 3,000 feet.

Although glaciers have provided the finishing touches on the landscape, a composite of tectonic events have left their imprint on the Wasatch Range. Overthrust faulting, intrusions of igneous rock (plutons), and folds can be viewed and appreciated from resorts. Rock outcrops exhibit diverse chapters of tectonic history, including gneiss, schist, and quartzite from ancient continental crust, marine limestone and sandstone from the former edge of the continent, conglomerates shed from eroding mountains, and granite and tuff from volcanic activity.

SURVEY NOTES

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, information rich 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.

Interactive Maps Available on the UGS Website:


VIEW ALL INTERACTIVE MAPS

Satellite image of the evaporation ponds at Intrepid Potash Inc.’s mining operation near Moab. Image from Google Earth © 2018 Google.

SURVEY NOTES

Glad You Asked: What Are Those Blue Ponds Near Moab?

By Stephanie Carney


If you have ever visited Dead Horse Point State Park, you may have noticed bright blue ponds glistening off to the east. These are not a mirage but are solar evaporation ponds used in the process of mining potash. The mine is currently owned and operated by Intrepid Potash Inc., and the ponds cover about 400 acres of land 20 miles southwest of Moab.

Sylvite from Intrepid's potash mine, Moab, Utah.

Sylvite from Intrepid’s potash mine, Moab, Utah.

Potash, a water-soluble potassium salt, is solution mined from the Paradox Formation more than 3,000 feet below the ground. Water from the Colorado River is injected down through a well into the potash-bearing strata, where it dissolves the salts. The resulting brine is extracted from a different well and pumped into the evaporation ponds. Blue dye is added to the water to enhance evaporation. The dye increases the absorption of sunlight and therefore increases the rate of evaporation. As evaporation progresses, the ponds become shallower and turn shades of light blue while the potash precipitates out of solution and is deposited on the bottom of the pond. The ponds turn a tannish brown color when nearly all the water has evaporated and the potash is ready to be harvested.

Satellite image of the evaporation ponds at Intrepid Potash Inc.’s mining operation near Moab. Image from Google Earth © 2018 Google.

Satellite image of the evaporation ponds at Intrepid Potash Inc.’s mining operation near Moab. Image from Google Earth © 2018 Google.

“Potash” is a general term that refers to a variety of potassium salts, such as potassium chloride (KCl), that are mainly used in fertilizer products, but also in the production of soap, glass, ceramics, and batteries. Historically, the term refers to potassium carbonate (KCO3), which is obtained by combining ash from burned plant material (usually hardwood trees) with water in large iron pots. Through evaporating and leaching of the “pot ash,” a residue of potassium carbonate is left behind that historically was used in the process of making soap or glass and ceramic products as early as A.D. 500. In North America in the 17th and 18th centuries, potash became an important industrial chemical and agricultural commodity. Large asheries were built to process the timber cleared and burned by settlers as they expanded westward across the U.S. By the mid-19th century, however, asheries became obsolete after a large deposit of natural potash was discovered in Germany and the birth of potash mining began. Natural potash deposits occur all over the world, but the largest reserves are in Canada. Other significant deposits are in Russia, Belarus, China, Israel, Jordan, and the U.S.

Schematic diagram of solution mining at Intrepid Potash Inc.’s Moab operation.

Schematic diagram of solution mining at Intrepid Potash Inc.’s Moab operation.

The potash mined near Moab is from the Pennsylvanian-age Paradox Formation, which was deposited between 315 and 310 million years ago in the Paradox Basin. During the Pennsylvanian period, the basin was an embayment to a large ocean and experienced cycles of open-marine conditions with freely circulating ocean water and restricted-marine conditions where access to the open ocean was blocked. During open-marine conditions, layers of shale, siltstone, limestone, and dolomite were deposited. When the basin was closed, the hot and dry climate during this time led to high rates of evaporation, and layers of salt were deposited. The salt is mostly halite (NaCl), but layers of sylvite (KCl) and carnallite (KMgCl3.6H2O) were also deposited.

Geologists have identified at least 29 cycles in the Paradox Formation, each represented by a specific sequence of sedimentary and evaporite rock layers, though only 18 cycles are known to contain potash minerals and only a few of those may have economically viable deposits. Individual salt deposits can be up to 1,000 feet thick in some places in the basin. Under the pressure of overlying strata, salt becomes ductile and because it is less dense than other rocks, it moves upward creating folds and diapirs. The Cane Creek anticline, in which the Intrepid potash mine is located, is a large, broad fold created by salt moving upward and bowing the rock layers above it. The potash mined by Intrepid is from Paradox Formation salt cycles number 5 and 9, which occur near the top of the formation. The salt is about 200 feet thick in cycle 5 and about 150 feet thick in cycle 9. The mined potash zone within each cycle, however, is much thinner, typically less than 10 feet thick.

Paleogeographic map of Utah during the Pennsylvanian period, approximately 308 million years ago, showing the Paradox Basin as an embayment to a western ocean (map modified from Ancient Landscapes of the Colorado Plateau by Ron Blakey and Wayne Ranney).

Though the cyclic deposits of the Paradox Formation were discovered in the 1920s, it was not until the mid-1950s during exploration for oil and natural gas that a potential economic potash resource was discovered within the Cane Creek anticline. By the early 1960s, the Texas Gulf Sulfur Company had built an underground mine and began room-and-pillar mining the potash from cycle number 5. Before operations began in 1964, however, an explosion of methane gas trapped 23 men, 18 of which were killed, during construction of the mine.

Because of hazardous gas pockets, high mine temperatures, and the thin, contorted, and difficult-to-mine potash layer, the operation was converted to solution mining in 1970.

The U.S. Geological Survey estimates that the Paradox Basin contains around 2 billion tons of potash resource, though depth to the resource (more than 5,000 feet in some areas) and complex geology have made exploration for economic deposits challenging. The current market price for potassium chloride, the most commonly produced form of potash, is about $200 per short ton, but price has been quite variable in the last decade. Intrepid’s capacity is about 100,000 short tons per year of potassium chloride, from their Moab operation, which is the only potash mine in the basin. Intrepid’s Moab operation along with two other operations in other parts of Utah (see Survey Notes, v. 44, no. 3, p. 1-3) produced 444,000 short tons of potash in 2017 (which includes both potassium chloride and potassium sulfate), the value of which was approximately $210 million. Utah and New Mexico are the only two states that currently produce potash. Because potassium is an essential nutrient for life and there is no substitute, potash mining in Utah likely has a bright and long future.

Glad You Asked: What Are Ice Caves?

By Jim Davis

Ice caves are caves in bedrock that host year-round ice. They differ from caves formed within ice, which are designated glacial caves. Ice caves are exceptional because they are not only scarce, but they are located far outside zones of permafrost—at low elevations (near sea level) and low latitudes (between around 30° and 70°), where they maintain a much lower average annual temperature than that of the air above. How cold temperatures persist in these spaces is a matter of cave geometry; the physical properties of air, water, and rock; the weather; and time. In Utah, ice caves are well developed in limestone caves and sinks in the Bear River Range, Uinta Mountains, and other areas such as talus slopes and lava flows.

American explorer Edwin Swift Balch (1856–1927) attributed much of the cause of ice caves to The Winter’s Cold Theory, the idea that the cold of the winter perpetuates through the summer. Balch took the presence of ice at the entrance of caves as evidence for the theory, noting that cold winter air is a requirement for ice cave formation and that ice had never been found beyond 200 meters (650 feet) from the entrance of a cave or deeper than 150 meters (490 feet). Therefore, the presence of year-round ice was due to capture and retention of cold from the previous winter rather than any natural processes operating in the cave.

Ice caves are differentiated into two types by air flow and cave structure: static ice caves and dynamic ice caves. Static ice caves flood with cold air in winter and have little air circulation in the summer, with the chilly, dense air settling in and remaining stable. Entrances in these caves are higher than the downward-sloping body of the cave and are referred to as “cold sock,” “cold pocket,” or “cold trap” caves. Conversely, dynamic ice caves have low entrances, an upward-sloping body, and conduits to the surface at the top of the cave. Dynamic ice caves are cooled by the “chimney effect,” where cold air is sucked up the entrance in winter as warm air exits the above conduits. Air flow is reversed in summer as cold air drains downslope out the entrance and warm air is drawn in through the higher conduits. The result is a continuous annual draft of cold air at the lower section of the cave. Dynamic air circulation also produces freezing talus slopes, which can be thousands of feet below areas of permanent ice.

Ice formation requires a source of water. Fractures and fissures in the bedrock allow water to seep in and freeze, or precipitation or runoff enter directly into the cave or sink. Masses of ice and snow in the cave from previous winters thwart rising temperatures in summer, as available heat energy is sunk into melting or sublimating the ice (latent heat) and warming water (specific heat) rather than warming the cave air. Once a cave builds up a sizable mass of ice and a large volume of the surrounding bedrock becomes cold, thermal inertia propels frigid temperatures through the heat of summer.

Duck Creek Ice Cave, formed in a sinkhole on the Markagunt Plateau, is an example of a cold trap ice cave. Duck Creek is small and, although always cool, does not quite meet the strict definition of an ice cave, often melting out in late summer. Similarly, the namesake of Ice Cave Peak in the Uinta Mountains, previously containing multiyear ice, has reportedly melted out. A classic disappearing stream, Big Brush Creek Cave, estimated at nearly 5 miles in length, is not just a cold air sink but a water sink consuming Big Brush Creek into its lengthy passageways. The Vernal Express wrote in 1893 “. . . it is called the Ice Cave because all summer long the entrance, to a depth of several hundred yards, is half filled with glittering ice . . .” During years of torrential spring runoff, the heat from floodwaters melts all the ice in the cave. An immense bluish ice column just inside the entrance has endured through multiple years in historical times, reported in August 1899 in the Salt Lake Herald as being “eight feet in diameter and reaches from the ceiling to the floor” and “would perhaps remain forever were it not for the rush of an occasional flood, which sweeps it away and into the depths below.”

Ice has been reported beneath talus slopes in the Wasatch Range and Wasatch Plateau, and in the blocky lava flows of the Black Rock Desert. An extraordinary example is in the Ice Springs lava flow “cave” in Millard County where the annual mean air temperature is around 52°F, but the surface temperature of the dark basalt can exceed 140°F in summer. In his 1890 monograph, Grove Karl Gilbert labeled this the “Natural Ice House” and observed ice there in late September. Gilbert hypothesized the ice was a result of (1) accumulation of cold water from melting snow, (2) protection from the sun by “a heavy cover conducting heat poorly,” (3) shelter from wind, and (4) evaporation. Much of the causes of the Ice Springs ice cave can be attributed to the “Balch effect,” where flattish areas with coarse, blocky materials can have ground temperatures that are more than 10°F cooler than the surrounding mineral soils. Winter air descends into the spaces between the blocks, displacing lighter, warm air. In the summer the cold air remains in the spaces between the rocks. The Ice Springs cave has been without ice at times, however, as reported by the Millard County Chronicle on September 10, 1942, as dry and bare as “Mother Hubbard’s Cupboard,” with the Chronicle later reporting 36-inch-long icicles on April 22, 1948.

Akin to ice in blocky fields, humans have reproduced the conditions to make ice in places where the thermometer never dips below freezing. Allahabad, India, has no frost days, but ice was created in winter under the favorable weather of a clear night (for radiative cooling) and a dry, light northwest wind (to utilize the latent heat of evaporation). With these conditions met, small, porous earthen jars were placed on a thick bed of loose, dry rice straw for insulation in a 2-foot-deep hollow dug in the soil. The jars were filled with water, placed 6 inches below ground, and covered with mats. In the morning, thin films of ice were collected from the jars and stored in an ice house. An ice crop could be harvested when overnight temperatures dipped below 52°F. The Indian ice industry thrived in the early 19th century until supplanted by the cheaper, higher-quality New England ice, or “crystal blocks of Yankee coldness,” cut from the coastal ponds of Massachusetts and shipped to tropical ports around the world.

Humans have also unintentionally recreated ice caves as tunnels, mines, shafts, and wells. The Salt Lake Mining Review wrote in 1916 of an ice tunnel near the divide between Little Cottonwood and American Fork canyons known as the “North Pole.” In winter and in summer, the old mine tunnel had a “solid wall of ice.”


Survey Notes, v. 51 no. 1, January 2019

This soil might just look like some crusty dirt. However it’s the crust on the dirt that makes this soil so very important. Tread lightly through this “Glad you Asked” article on soil crusts to find out more!

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Have you ever been on an outdoor adventure when you found yourself faced with some kind of geological feature, only you weren’t sure which one? ..It looks like Paul Bunyan’s Woodpile, but is this it?..

Check out our “Glad You Asked” article where you can learn more about how Geographic Names came to be officially recognized, and explore the online database of where these places are located!

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While the weather has been warm, and there’s not a lot of snow or ice around, it’s a great time of year to look at the Ice Age animals of Utah. Did you know that Great Salt Lake is the remnant of Ice Age lake, Lake Bonneville? Read more about this different age in Utah in our “Popular Geology” subjects HERE.

Trilobites are always a fun find when you’re exploring the outdoors, but how much do you know about Trilobites as living organisms? Maybe you’re just interested in finding your own Trilobite fossils. Read more about the little critters in our “Glad You Asked” article HERE!

Cooler weather is on its way, so we’ve got a cool “Glad You Asked” article to compliment the changing seasons! It’s a beautiful time of the year to get out into Utah’s geology. Maybe some of you have noticed these groovy rocks out on your outdoor adventures. What are those grooves in the rocks, and how did they get that way?

Read more about Glacial Striations and Slickensides HERE!