U    T   A    H       G   E   O   L   O   G   I   C   A   L   S   U   R   V    E    Y

Volume 43, Number 1...
The Director’s
      Perspective                                                      Although the increased rate of retir...
High-precision Global Positioning System (GPS) surveying of                   tionally, linear features of unknown origin ...
ground-water overdraft and resultant subsidence will likely cause                                               Based on t...
                                  M. Harty
  by Ashley H. Elliott and Kimm
Landslide maps for the northwestern
portion of the Kanab 30' x 60'
quadrangle as depicted in the earlier
UGS compilation (...
The Geologic Hazards Program has an ongo-     ...
The Bear Wallow landslide complex near Snowbasin
Glad You Asked
               What are the Roots of Geobotany?
by Jim Davis                                      Desert tr...
Survey Notes January 2011
Survey Notes January 2011
Survey Notes January 2011
Survey Notes January 2011
Survey Notes January 2011
Survey Notes January 2011
Upcoming SlideShare
Loading in...5

Survey Notes January 2011


Published on

Published by the Utah Geological Survey

  • Be the first to comment

  • Be the first to like this

No Downloads
Total Views
On Slideshare
From Embeds
Number of Embeds
Embeds 0
No embeds

No notes for slide

Survey Notes January 2011

  1. 1. U T A H G E O L O G I C A L S U R V E Y SURVEY NOTES Volume 43, Number 1 January 2011 UTAH'S GEOLOGIC HAZARDS
  2. 2. The Director’s Perspective Although the increased rate of retire- decade to maintain existing staffing ments represents a loss of valuable exper- levels. There is national concern about tise, it also represents opportunities for what has been called the “Great Crew new geology graduates to join the UGS. Change”: an aging workforce juxtaposed Today’s graduates leave college with dif- against an anemic supply of qualified and ferent skill sets than what their predeces- trained scientists and engineers (Status sors had—for example, almost all have of the Geoscience Workforce, American good computer skills and are GIS literate. Geological Institute Report, 2009). In addition, today’s geologic challenges Although a “Great Crew Change” seems require a broader geoscience skill set to have started at the UGS, we see little by Richard G. Allis compared to traditional geology needs evidence that the supply of graduates (or several decades ago. Despite the increased experienced candidates) is affecting the Over the past 12 months the UGS has had rate of retirements and resignations, we quality of applicants. Indeed, the number a staff turnover rate of close to 10 percent. have been able to fill all the openings with of students enrolled in Earth science post- Collectively, the outgoing staff represent talented people whom we hope will stay graduate programs at Utah’s universities a loss of over 200 years of experience. and have productive careers with the UGS. is reportedly strong. It remains to be seen About half of these were retirements, and The dominant degree for geoscientists at whether this situation will change once half were resignations. This turnover rate the UGS is a master’s degree (55 percent; the economy rebounds and the private is more than double what has been typical 30 percent have a bachelor’s degree and sector starts more aggressive hiring. for the UGS over the past 10 years. The 13 percent have a high turnover is due to a variety of factors, doctorate). This but one obvious factor has influenced the pattern is similar to retirements—that is the evolving age other state geologi- profile of staff geoscientists. Seven years cal surveys across ago the age profile for geoscientists at the the U.S., as is the UGS had a single peak between 45 and age profile with a 55 years old, and two-thirds of the staff peak between 50 were over the age of 45. Presently, that and 60 years old. age peak has moved seven years, and When these two a greater number of geoscientists are factors are consid- considering retirement. The peak has ered together, state shrunk in relative size, but the age profile geological surveys suggests the increased rate of retirements will need about will continue for another decade. A sec- 500 new master’s- ondary, younger, age peak is now showing level graduates up as replacements fill the vacancies. over the next Contents State of Utah Editorial Staff Vicky Clarke Geologic Mapping Grant Willis Gary R. Herbert, Governor Lori Douglas, Stevie Emerson, Jon King, Douglas Sprinkel, Jeremy Gleason, Jay Hill Janice Hayden, J. Buck Ehler, Department of Natural Resources Land Subsidence and Earth State Energy Program Kent Brown, Basia Matyjasik, Michael Styler, Executive Director Fissures in Cedar Valley.........................1 Chris Tallackson Don Clark, Bob Biek, Paul Kuehne Updated Landslide Maps of Utah ................4 UGS Board Denise Beaudoin, Jerriann Ernsten, Ground Water and Paleontology Kenneth Puchlik, Chair GPS Monitoring of Slow-Moving William Loughlin Jack Hamilton Brandon Malman, Jim Levy, Michael Lowe Will Chatwin, Deborah Boren, James Kirkland, Janae Wallace, Landslides .............................................6 Tom Tripp Alisa Schofield Alair Emory, Alex Dalpé-Charron, Martha Hayden, Hugh Hurlow, Liquefaction in the April 15, 2010, Mark Bunnell Donald Harris Sherry Childers, Stefan Wilson, Don DeBlieux, Kim Nay, M 4.5 Randolph Earthquake..................7 Kevin Carter (Trust Lands Alex Scott Paul Inkenbrandt, Lucy Jordan, Administration-ex officio) Glad You Asked ..........................................8 Geologic Hazards Steve Bowman Kevin Thomas, Rebecca Medina, Richard Giraud, William Lund, Walid Sabbah, Rich Emerson, Teacher’s Corner ........................................9 UGS Staff Greg McDonald, Jessica Castleton, Stefan Kirby, Scott Madsen, GeoSights .................................................10 Administration Gregg Beukelman, Chris DuRoss, Toby Hooker Survey News ............................................11 Richard G. Allis, Director Tyler Knudsen, Corey Unger, Energy and Minerals David Tabet Energy News ............................................12 Kimm Harty, Deputy Director Lisa Brown, Jim Ollerton, Robert Blackett, Craig Morgan, Barry Solomon, Adam McKean New Publications .....................................13 John Kingsley, Associate Director Mike Laine, Jeff Quick, Taylor Boden, Starr Losee, Secretary/Receptionist Geologic Information and Outreach Thomas Chidsey, Cheryl Gustin, Dianne Davis, Administrative Secretary Sandra Eldredge Tom Dempster, Brigitte Hucka, Design: Jeremy Gleason Kathi Galusha, Accounting Officer Christine Wilkerson, Patricia Stokes, Stephanie Carney, Ammon McDonald, Linda Bennett, Accounting Technician Mark Milligan, Stephanie Earls, Cover: An active landslide on the Wasatch Plateau in Ken Krahulec, Valerie Davis, Michael Hylland, Technical Reviewer Emily Chapman, Lance Weaver, the Seely Creek drainage. The lower landslide averaged Brad Wolverton, Sonja Heuscher, Robert Ressetar, Technical Reviewer Gentry Hammerschmid, Jim Davis, 14 feet of movement per year between 2004 and 2009. Mike Vanden Berg, Andrew Rupke, Photograph by Rich Giraud. Marshall Robinson Mark Gwynn Survey Notes is published three times yearly by Utah Geological Survey, 1594 W. North Temple, Suite 3110, Salt Lake City, Utah 84116; (801) 537-3300. The Utah Geological Survey provides timely scientific information about Utah’s geologic environment, resources, and hazards. The UGS is a division of the Department of Natural Resources. Single copies of Survey Notes are distributed free of charge within the United States and reproduction is encouraged with recognition of source. Copies are available at geology.utah.gov/surveynotes. ISSN 1061-7930
  3. 3. LAND SUBSIDENCE AND EARTH FISSURES IN CEDAR VALLEY, SOUTHWEST UTAH by William Lund, Tyler Knudsen, Paul Inkenbrandt, and Mike Lowe In May 2009, Enoch City contacted the Utah Geological Survey (UGS) to investigate a possible “fault” that was damaging streets, sidewalks, and curbs and gutters in a new subdivision in north Enoch. During a recon- naissance investigation, the UGS found a 2.4-mile-long earth fissure that had formed in response to land subsidence caused by ground-water over- draft of the local aquifer. In the affected subdivision, the fissure crosses Vertical displacement along the Enoch-graben-west fis- several undeveloped lots, and in addition to damaging streets and side- sure has damaged 3-year-old walks, vertical displacement across the fissure has reversed the flow direc- asphalt-concrete pavement tion of a sewer line so that it is no longer possible to gravity-drain sewage in the Parkview subdivision; effluent from the subdivision. The likely relation of the fissure to ground- view is to the south. water pumping was communicated to Enoch City, the Utah Division of Water Rights, Iron County, and the Central Iron County Water Conservancy District (CICWCD). The CICWCD subsequently funded the UGS to conduct a detailed investigation of the Enoch earth fissure, and to determine if land subsidence and earth fissures were affecting other areas in Cedar Valley. Although earth fissures have been documented in the rural Escalante Desert, the discovery of the Enoch fissure is significant because it is the first one in Utah that has encroached into a develop- ing area. In other western states, land subsid- ence and earth fissures have caused hundreds of millions of dollars in damage to buildings, roads, bridges, railroads, utilities, well casings, dams, canals, and other infrastructure. Our investigation focused on an evaluation of water-table decline and the distribution, thick- ness, and texture of basin-fill deposits in Cedar Valley—these are all critical components to land subsidence and fissure formation in the arid southwestern United States. A comparison of historical water-level data with new UGS mea- surements shows that ground-water discharge in excess of recharge since 1939 has lowered the ground-water surface in Cedar Valley by as much as 114 feet. Using nearly 300 well drillers’ logs, we produced a map and simplified cross sections of Cedar Valley’s basin-fill sediments that show a high percentage of fine-grained material (chiefly clay) that is particularly prone to compaction upon dewatering. Location of earth fissures in Cedar Valley. White lines are contours of approximately equal ground-surface elevation change (feet) since 1950, based on comparison of historical leveling and modern GPS data. JANUARY 2011 1
  4. 4. High-precision Global Positioning System (GPS) surveying of tionally, linear features of unknown origin observed on aerial photos benchmark elevations indicates that more than 110 square miles of and the presence of an isolated sinkhole south of State Route 56 are the ground surface in Cedar Valley has subsided as much as 4 feet generally along trend with the earth fissures west of Quichapa Lake, since 1950. In response to the land subsidence, at least 3.9 miles and may indicate the possibility of a more extensive zone of fissuring (total length) of earth fissures have formed in the western and north- on the west side of Cedar Valley. eastern parts of Cedar Valley. The Enoch-graben-west earth fissure Our investigation results show that the maximum amount of land is the longest (2.4 miles) fissure, and is the only fissure that exhibits subsidence and earth fissure formation in Cedar Valley coincide with vertical displacement. Significant fissure-related damage in Cedar areas of significant ground-water-level decline and the presence of Valley is currently limited to the partially developed Parkview subdi- compressible fine-grained sediment in the subsurface. We conclude vision in Enoch City; however, to the north the Enoch-graben-west that long-term ground-water pumping in excess of recharge is the fissure also trends through and has displaced the ground surface cause of the land subsidence and earth fissures in Cedar Valley. If in a heavily used livestock pasture/feeding area creating a poten- ground-water levels in Cedar Valley continue to decline 3 feet per year tial for ground-water contamination. Aerial photographs show that (current average rate of decline), average basin-wide subsidence will the Enoch-graben-west fissure began forming more than 50 years likely continue at a rate of 0.04 to 2.4 inches per year. Continued ago, and that the fissure grew approximately 900 feet to the south between 1997 and 2006. The main developed area of Enoch City lies approximately 1000 feet south of the current fissure tip. Addi- Schematic cross section showing water wells and the distribution of fine-grained sediments across southern Cedar Valley; see map of change in ground-water depth for location of cross section. ABOUT THE AUTHORS 2 Tyler Knudsen is a Project Geologist with the 3 Paul Inkenbrandt graduated from the University of Southern 4 Mike Lowe has been with the UGS since 1989 and has UGS Geologic Hazards Indiana with a B.S. degree in been involved with geologic- 1 William Lund has 38 years of experience as an engineering Program. He has a B.S. Geology in 2005. He went on to mapping projects, geologic-hazard geologist—7 years with geotechnical consulting firms in degree in Geology from work for the Kentucky Geologi- assessments, and ground-water Arizona, California, and Oregon, and 31 years with the UGS. the University of Utah and cal Survey for a year, and then investigations. He is currently He is a former deputy director of the UGS, presently is the an M.S. degree in Geol- moved to Utah to attain an M.S. manager of the Ground-Water and Geologic Hazards Program Senior Scientist, and is manager ogy from the University of degree in Geology from Utah Paleontology Program. Prior to of the UGS’ Southern Regional Office in Cedar City. He Nevada, Las Vegas. Since State University. He completed joining the UGS, he worked as a is a Licensed Professional Geologist in Utah, Registered joining the UGS in 2006, his thesis on Cache Valley aqui- well-site geologist in the petroleum Geologist in Arizona, and Certified Engineering Geologist Tyler's work has focused on fers in fall 2010. He has been industry in Texas from 1981 to in Oregon, and is a past president of the Intermountain geologic-hazard mapping with the UGS Ground-Water 1982, and was County Geologist Section of the Association of Engineering Geologists, Utah and paleoseismic studies and Paleontology Program since for Davis and Weber Counties from Geological Association, and Dixie Geological Society. in southwestern Utah. September 2009. 1985 to 1989. 2 SURVEY NOTES
  5. 5. ground-water overdraft and resultant subsidence will likely cause Based on the results of our study, the CICWCD has provided addi- existing fissures to lengthen and new fissures to form that may even- tional funding for the UGS to prepare suggested policy recommen- tually impact developed neighborhoods in Cedar Valley. Additionally, dations for managing the Cedar Valley aquifer to prevent future earth fissures could provide a direct path for contaminated surface subsidence and fissure formation, and for preventing additional water to reach the Cedar Valley aquifer, which is a major source of infrastructure damage in existing subsidence areas where fissures culinary water. either have formed or may form in the future. EXPLANATION ! ( Well estimated as pumping > 200 acre-ft/year Fissure EXPLANATION ! ( Change in ground-water depth EXPLANATION pumping > 200 acre-ft/year Cross section !! (( ! Valley ( Well estimated as ! ( in Cedar Valley from September ( Fissure floor shallow bedrock ! Well estimatedandpumping > 200 acre-ft/year Bedrock as 1939 to October 2009. Fissure section Cross Ground-water Level Change Cross section Valley floor ft (negative indicates ground-water rise) Valley floorand shallow bedrock Bedrock Bedrock - 114 Change 101 Level Ground-water and shallow bedrock Ground-waterindicates ground-water rise) ft (negative Level Change 91 - 100 ft (negative indicates ground-water rise) 101 - 114 81 - 90 101 -- 114 91 100 1 91 -71 - 80 81 100 - 90 T34S 81 -61 - 70 71 90 - 80 T34S 71 -51 - 60 61 80 - 70 T34S 61 - 70 51 - 60 41 - 50 51 - 60 41 - 50 41 -31 - 40 31 50 - 40 31 -21 - 30 21 40 - 30 21 -11 - 20 11 30 - 20 11 --20 1 10 1 - 10 1 -2 - 0 - 10 -2 - -2 - 0 0 0 1 2 3 4 00 1 1 2 2 3 Miles 34Miles 4 ! ( ´ Miles ! ( ´ ! ( ! ( ! ( ! ( ! ( ! ( ! ( 2 ! ( !! (( ! ( ! ( ! ( ks 130 ! Enoch ( ae s ka 130 ! Enoch ! ( ! ( ( eP ! ( rePe ! ! ( ( ! ( ! ( ! ( ! (! ( ! ! ( ( ! ( ! ( rhe ! ks ! ( ( ! ( e Te 130 ! ( Enoch ThTh P ea ! ( ! ( ! ( T35S ! ( The ! ( ! ( T35S ! ( ! ( ee ! ( ! ( ! ( ! ( ! ( ! ( T hr ! ( ! ( ! ( ! ( The Study Area ! ( ! ( !! (( ! ! ( ( ! ( ! ( T35S Study Area ! ( ! ( ! ! ( ( ! ! ( ( ! ( ! ( ! ( ! ( ! ( ! ( ! ! ! ( ( ( ! ( ! ( ! ( ! ( ! ( ! ( Study Area ! ( ! ( ! ( ! ( ! ( ! ( 3 ! ( ! ( ! ( ! ! ( ( ! ( ! ( ! ( R13W R13W ! ( ! ¨ ! ( ¦ ( (( § ( !! ¦ ! 15 ! ! § ( ( ¨ 15 ! ( 56 ! ( ! ( ! ( ! ( 56 ! ( Cedar Cedar ! ( City 14 City ! ( 14 Cross Cross Hollow !! (( Hollow R13W !! (( Hills Hills § ¦ ¨15 ! ( ! ( T36S T36S ! ( 56 Hamilton Hamilton Cedar Fort 4 Fort City ! ( ! ( Cross ! ( ! ( Hollow !! (( Hills ! ( ! ( ! ( T36S ! ( ! ( ! ! ( ( ! ! ( North ( ! ( North Hills ! ( Hills Hamilton ! ( Fort T37S T37S ! ( ! ( ! ( ! ( R12W R11W R10W R12W R11W ! ( R10W ! ( ! ( JANUARY 2011 3 ! ( ! ( North
  6. 6. UPDATED LANDSLIDE MAPS OF UTA H M. Harty by Ashley H. Elliott and Kimm more than 5 percent of Utah. The maps published a statewide show various types of landslides includ- map and database compila- ing generally deep-seated, slow-moving tion of landslides using pre-1989 landslides (such as rotational and trans- Significant economic losses are associ- published and unpublished sources. lational slides); fast-moving, generally ated with landslides, and Utah contains Since then, many new geologic maps and shallow landslides (debris flows and numerous landslides and landslide-prone updated studies have been published slides); earthquake-induced landslides geologic units. In the early 1980s and that show additional landslide locations. (lateral spreads and flows); and land- mid-2000s, above-normal precipitation In an effort to incorporate this new infor- slides undifferentiated from other Qua- resulted in many landslides that caused mation and improve the understand- ternary deposits (such as talus, colluvial, millions of dollars in losses. Many land- ing of landslides and their distribution and rock-fall deposits). In addition, the slides in Utah result from the reactiva- throughout Utah, we created an updated GIS data provide more-specific landslide tion of pre-existing landslides, hillslope version of the landslide maps and data- attribute information including depth of modifications of landslide-prone geo- base using a geographic information landslide deposit, type of material, type logic units, and natural gravity-related system (GIS). The updated information of movement, historical landslide events, downslope earth movements. Exposure is available in GIS format as well as PDF landslide-prone geologic units, possible to landslide hazards only increases as format and depicts 46 topographic land- movement causes, and original map ref- development expands onto hillslopes, slide maps at a scale of 1:100,000 (1 inch erences. onto alluvial fans at the mouths of flood- = 1.6 miles). The new maps add land- prone canyons, and into other landslide- Local jurisdictions, developers, geotech- slide data documented in 240 geologic nical consultants, the general public, prone areas. maps and internal UGS landslide inves- and others interested in landslides can To increase awareness of the land- tigations completed between 1989 and use the landslide maps and database to slide hazard in Utah, the Utah Geologi- mid-2007. These new data allowed us identify potential landslide hazards and cal Survey (UGS) in 1991 to refine some of the the need for site-specific geologic-hazard existing landslide and geotechnical investigations in areas boundaries and add of proposed development. Although approximately 12,000 proper planning and avoidance of land- to the approximately slide-prone areas are usually the best 10,000 previously ways to reduce landslide-related losses, documented. avoidance is not always possible. Where The maps and asso- asso avoidance is not possible, site-specific ciated GIS data geologic-hazard and geotechnical inves- provide a way to tigations can identify engineering tech- identify the loca loca- niques that may be used to stabilize tion and extent of slopes or reduce the impacts from land- previous landslid landslid- slides. ing. The more The updated Landslide Maps of Utah than 22,000 land land- (2010, by A.H. Elliot and K.M. Harty) slides depicted on are available on DVD as Utah Geological the maps cover Survey Map 246DM. Examples of damage caused by landsliding in the mid-2000s. A guest house destroyed by a 2005 rock fall in Provo (above) and damage to a house in South Weber caused by a rapidly moving landslide in 2006 (left). 4 SURVEY NOTES
  7. 7. Landslide maps for the northwestern portion of the Kanab 30' x 60' quadrangle as depicted in the earlier UGS compilation (below) and the updated compilation (right). The updated map shows added landslides and redefined landslide boundaries based on new information. For additional information on landslides in Utah, refer to the following UGS publications: Case, W.F., 2001, Landslides – what they are, why they occur: Utah Geological Survey Public Information Series 74, available online at geology.utah.gov/online/pdf/pi-74.pdf. Christenson, G.E., and Ashland, F.X., 2007, A plan to reduce losses from geologic hazards in Utah – recommendations of the Governor’s Geologic Hazards Working Group 2006-2007: Utah Geological Survey Circular 104, 30 p. Deep or unclassified landslide – Generally 10 feet (3 m) thick or more and shows characteristic Giraud, R.E., and Shaw, L.M., 2007, Landslide landslide morphology. May include areas where landslide density is too great to show individual susceptibility map of Utah: Utah Geologi- landslides separately. cal Survey Map 228DM, 11 p., 1 plate, scale Landslide undifferentiated from talus and/or colluvial deposits – May include deep or shallow 1:500,000. landslides mapped with talus and/or colluvial deposits. Utah Geological Survey, 1998, Homeowner’s Landslide and/or landslide undifferentiated from talus, colluvial, rock-fall, glacial, and soil- guide to recognizing and reducing landslide creep deposits – May include deep or shallow landslides mapped with talus, colluvial, rock-fall, glacial, and/or soil-creep deposits; primarily mapped and compiled by Roger B. Colton, U.S. Geo- damage on their property: Utah Geological logical Survey. Survey Public Information Series 58, available online at geology.utah.gov/online_html/pi/ Not classified – Includes areas not mapped in the original studies compiled for this map, as well as mapped areas with no identified landsliding. pi-58/index.htm. JANUARY 2011 5
  8. 8. GPS MONITORING OF SLOW-MOVING LANDSLIDES The Geologic Hazards Program has an ongo- by Richard Giraud and ing long-term Global Positioning System (GPS) Greg McDonald monitoring program to determine movement activity in several northern Utah landslides. Landslides may move so slowly that their move- ment is imperceptible to humans. A geolo- gist investigating a slow-moving landslide may determine it to be dormant and stable, based In contrast, slow-moving landslides generally on the landslide’s appearance and short-term An example of a clearly active display the following: landslide on the Wasatch Pla- movement monitoring. However, the landslide could be moving slowly, and the consequences • possible extensive vegetation cover, teau in the Seely Creek drain- age (above). The landslide of assuming the landslide is stable and safe to • smooth, undulating surface, shows a lack of vegetation, build on could be disastrous. Therefore, while • lack of ground cracks, and hummocky rough surface, and these landslides appear stable, precise long- • faint landslide head, toe, and internal distinctive head and toe fea- term measurements are needed to evaluate if features. tures. The lower landslide av- they are moving. Slow-moving landslides that eraged 14 feet of movement per we have targeted for monitoring can move as Ground cracks and other sharp features may year between 2004 and 2009. slowly as half an inch per year or less. develop on slow-moving landslides; however, Photograph taken September Determining if a landslide is actually moving erosion generally mutes and obscures these 24, 2009. (See front cover.) using geologic observations of the landslide sur- features as they develop. On a slow-moving face can be difficult in the case of slow-moving landslide, the features can erode faster than landslides. Landslides that move several feet they develop, giving the landslide a dormant and per year are generally easy to recognize as active because the landslide surface is rough, appears disturbed, and displays other freshly developed landslide features. Landslides with recent sig- nificant movement commonly display the fol- lowing: • lack of vegetation or disturbed vegetation (for example, tilted trees), • hummocky, rough surface, • fresh ground cracks, and • sharp, distinctive landslide head, toe, and GPS base station and transmitting antenna used for internal features. monitoring slow-moving landslides (left). The base sta- tion site is on bedrock and is assumed to be stationary with respect to nearby monitored landslides. 6 SURVEY NOTES
  9. 9. The Bear Wallow landslide complex near Snowbasin (left) is an example of a slow-moving landslide, show- ing vegetation cover and a smooth undulating landslide surface. Parts of some internal landslides within the complex have moved as rapidly as 8 inches per year, but most monitored points move 1 inch or less per year. Photograph taken December 3, 2009. LIQUEFACTION IN THE APRIL 15, 2010, M 4.5 RANDOLPH stable appearance when the landslide is actually unstable and moving slowly. Multiple measurements also provide movement rates and direction for dis- EARTHQUAKE One method of determining slow rates tinct survey points on a landslide. A by Chris DuRoss of landslide movement is with a survey- history of landslide movement aids grade GPS instrument that uses infor- in anticipating future landslide move- mation broadcast by a satellite network ment, managing landslide movement The UGS conducted a brief field reconnaissance to accurately determine the location of problems, and providing information following the April 15, 2010, magnitude (M) 4.5 points on the landslide within approxi- to aid subsequent landslide investiga- Randolph earthquake, which occurred about mately 0.5 inch horizontal and 2 inches tion. 6 miles northeast of Randolph near the base vertical. GPS monitoring involves The Geologic Hazards Program cur- of the Crawford Mountains in northern Utah. remeasuring the points on the land- rently monitors several slow-moving The Randolph earthquake was unusual in that slide surface over time. Depend- or potentially slow-moving landslides it generated liquefaction (rare for M <5), includ- ing on annual precipitation, several in northern Utah. Site selection for ing sand boils (eruptions of liquefied sand) years of monitoring may be needed monitoring is based on nearby urban along the Bear River about a half mile west of to identify movement. Our monitor- development, risk, and available moni- the earthquake epicenter. The earthquake is ing program includes collecting GPS toring resources. The following land- thus one of the smallest recorded with modern measurements once a year unless sig- slides are currently monitored: instrumentation to generate liquefaction. We nificant movement is detected; in that attribute the occurrence of liquefaction to highly • Green Pond and Bear susceptible sediments very near the epicenter; case, measurement frequency may be Wallow, Snowbasin Road, increased to collect additional data however, anomalously high ground motions State Route 226, Weber may have also contributed to the liquefaction. while the landslide is moving. Land- and Morgan Counties. slides rarely move uniformly along their entire length, so repeated moni- • Creekside Drive, Mountain Sand boils (eruptions of liquefied sand) formed along the toring of points distributed through- Green, Morgan County. Bear River during the April 15, 2010, Randolph earth- out the entire landslide is necessary to • Springhill Drive, North quake. Scale card is about 6.5 inches long. identify movement and plot its distri- Salt Lake, Davis County bution. Additional monitoring points (example of a slow-moving are needed outside the landslide to landslide in a subdivision). determine landslide boundaries. • Potato Hill and Little Valley, Our main goal is to detect repeated Draper, Salt Lake County. landslide movement over a period of several years in landslides that appear • Unnamed landslide near to be dormant or slow moving. If Mill Hollow Reservoir, movement is detected, our monitoring Wasatch County. program can be refined to determine • Coal Hill, east of Zion if the landslide moves continuously National Park, State throughout the year or seasonally (gen- Route 9, Kane County. erally during the spring). Movement Monitoring results for the Spring- patterns can then be compared with hill Drive landslide are available at records of precipitation and ground- geology.utah.gov/utahgeo/hazards/ water levels to see what associations landslide/springhill09/index.htm. may exist. Other studies have shown Additional information on landslides that periods of above-normal precipita- in Utah is available at geology.utah. tion and high ground-water levels com- gov/ghp/index.htm. monly trigger landslide movement. JANUARY 2011 7
  10. 10. Glad You Asked What are the Roots of Geobotany? by Jim Davis Desert trumpet (Eriogonum inflatum), above, on the Colorado Plateau, June 1949. Desert trumpet is an indicator plant for sulfur-rich soils and gypsiferous ore deposits. Photo by Helen Cannon, courtesy of the U.S. Geological Survey. Plants can enlighten geologists as to the rock beneath. Geobotany, also called Prince's plume (Stanleya pinnata), below, tolerates highly mineralized soil and indicates selenium and phytogeography, is the scientific study of sulfur-rich soils, and gypsum deposits. Photo courtesy of Wayne Padgett, Bureau of Land Management. the distribution of plants. Climate is con- sidered the primary control on plant life, each claim several endemic species. In but within a particular climatic region the the Uinta Basin, Graham’s beardtongue rock beneath soil—known as the parent is found only on sparsely vegetated expo- material of soil—is typically the key sures of the upper Green River Formation factor influencing the vegetation growing oil shale deposits. Graham’s beardtongue above. Rock ultimately determines soil could come under increasing threat in moisture characteristics, nutrient avail- the future due to loss of habitat from oil ability, and concentrations of essential and gas exploration, drilling, and tar sand elements. Therefore, certain plants and oil shale mining, and consequently are associated with specific rock types. has been proposed for a threatened status Limestone, dolomite, shale, gypsum, listing under the Endangered Species chert, gabbro, rock salt, and ultramafic Act. rocks (e.g., dunite, peridotite, serpenti- nite), for example, are known for their The use of plants to find ore bodies is distinctive floras. Since before the advent called geobotanical prospecting. It has been of agriculture humans have used plants effective in locating mineral deposits as a guide to find sought-after rocks and worldwide, such as tin and tungsten plants as a tool for prospecting carnotite, minerals. Today, the methodologies of in England; nickel, cobalt, and iron in a radioactive uranium ore. Cannon con- geobotany are still applicable, practical, Russia; copper and silver in Montana; firmed that Astragalus species (including and even cost-effective to the geologist. bitumen in California and by the Caspian milk-vetch and locoweed) pinpoint areas Sea; and copper and nickel in central of selenium-rich uranium ore. Cannon Dramatic changes in vegetation can occur and southern Africa. There are three also documented 50 other plants on with changes in geology. In mountain commonly applied methods in geobotan- the plateau associated with mineralized ranges of the Great Basin, big sagebrush ical prospecting: (1) mapping of indicator ground. growing on sandstone abruptly transi- plants, (2) assessing plant appearance tions to bristlecone pine on dolomite. and physiology, and (3) chemical testing For half a century, aerial photo interpreta- The distribution of the California poppy of plants known to accumulate specific tion has been used as a tool for locating in Arizona closely correlates with copper elements. indicator plants, anomalous vegetation mineralization, which in turn corre- patterns, and evaluating plant health. sponds with fault lines. In Utah, many Indicator Plant Mapping Indicator plant mapping has gained a of the state’s endemic plant species powerful tool in the past few decades Indicator plant species mark sites that are (those found nowhere else on Earth) are with remote sensing, or the imaging of likely enriched in a particular element or restricted to growing on a single geologic Earth via satellite. Remote sensing uses mineral. Usually these places are toxic or unit—the Green River, Moenkopi, parts of the electromagnetic spectrum, intolerable for other plant species, elimi- Navajo, Mancos, and Chinle Formations such as infrared or ultraviolet light, to nating any competition. Here in Utah, detect plant species otherwise undetect- prince’s plume grows in selenium- and able when just the visible-light spectrum calcium-rich soil; tufted evening-prim- is examined. These plants are then used rose, onion, wild buckwheat in calcium- to glean clues about an area’s geology. and sulfur-rich soil; and desert trumpet Because so much of Earth’s bedrock is grows in gypsiferous soil. covered by vegetation, interpreting the In southeastern Utah on the Colorado flora from imagery derived from remote Plateau, geologist Helen Cannon in the sensing has been an increasingly impor- 1940s and 1950s pioneered the use of tant technique in geologic mapping. Graham's beardtongue (Penstemon grahamii) is endemic to Utah's Uinta Basin and the adjacent Piceance Basin of Colorado. It grows only on the upper Green River Formation. Photo courtesy of Michael Vanden Berg. 8 SURVEY NOTES