Correcting Ice Sheet Mass Balance for Refreezing of Infiltrated Surface Melt: The Forgotten Grand Problem
by W. Tad Pfeffer
Abstract: Recent images showing vastly expanded regions of surface melt on the Greenland Ice Sheet are testimony to the climatic anomalies now occurring in the Arctic with ever greater frequency and duration. What these images tell about the overall mass balance of the Greenland Ice Sheet, on the other hand, is another question, not directly addressed by determination of surface melt rates. The significance of that increased melt depends greatly upon whether the water thus produced runs off directly to the ocean via near-surface hydrologic pathways, or drains to the base of the ice sheet where it may influence ice sheet sliding, or percolates some short distance vertically to be retained, possibly as saturated firn or as refrozen “infiltration ice.” At present the observational evidence needed to investigate this problem is sparse (but not altogether absent), and relevant theory is in development, but incomplete. Significantly, there is still no observational method for directly measuring the outflow of water from the Greenland Ice Sheet, and all evaluations of the surface mass balance of the ice sheet depend to some extent on modeled runoff, based on unconfirmed assumptions about the mobility and transport of water once it has been generated by surface melt.
The fate of surface-generated melt on the Greenland Ice Sheet has been the focus of studies going back to the 1950s and 1960s when research motivated by Cold War military objectives was conducted on internal firn structure, and trafficability of the ice sheet surface. The earliest comprehensive global studies on future sea level rise began in the late 1970s, leading to research specifically on Greenland’s overall mass balance. At that time, retention of infiltrating melt water by refreezing was identified as a crucial unknown to be resolved if the mass balance of polar glaciers, and the Greenland Ice Sheet in particular, was to be modeled based on projections of future temperature. Subsequent developments in surface energy balance measurements and modeling have yielded a robust capacity to model the generation of surface melt, but to date the near-surface transport of that melt has at best been handled by one-dimensional models of infiltration and refreezing. Observations show, however, that melt water infiltration in subfreezing, heterogeneous, stratified firn is highly non-linear and typically involves the development of vertical channels, or “flow fingers,” where water flows downward through firn of higher relative saturation and hydraulic conductivity. The differences in transport characteristics between one-dimensional, homogenous and three-dimensional, heterogeneous infiltration can be dramatic.
I will review the fundamental physics of the problem of melt water infiltration in cold, permeable snow, trace its history as a research issue in the context of forecasting future sea level rise, discuss some interesting and very new developments, and make an initial evaluation of the effect of this unsolved problem on sea level projections.
Biography: W. Tad Pfeffer is a glaciologist, geophysicist, and photographer at the University of Colorado at Boulder. He is a Fellow of the University’s Institute of Arctic and Alpine Research and Professor in the Department of Civil, Environmental, and Architectural Engineering. Pfeffer’s research is focused on glacier mechanics and dynamics, and particularly on dynamics of oceanending glaciers and glacier contributions to sea level. He has done field research for more than 30 years in glacier regions from Alaska to Antarctica to the summit of Mt. Kilimanjaro. Pfeffer also leads the long-term study of Columbia Glacier, on Alaska’s South Central Coast, one of the world’s most extensively studied and most rapidly changing glaciers. He has served as an advisor to the United Nations Environmental Program (UNEP), the Arctic Monitoring and Assessment Program (AMAP), and is a Lead Author for Chapter 13 (Sea Level Change) in the IPCC Fifth Assessment/Working Group I. In addition to his scientific work, Pfeffer’s photography has appeared in many publications in the US and Europe. He is the author of The Opening of a New Landscape: Columbia Glacier at Mid-Retreat, published by the American Geophysical Union in 2007.
Evaluating the History of Vadose-Water Flow Through Yucca Mountain, Nevada, Using Secondary Hydrogenic Minerals – A Case for Slow and Steady
by James B. Paces, Ph.D.: USGS, Geoscience and Environmental Change Science Center, Denver, CO
Abstract:Yucca Mountain, the erstwhile repository site for the Nation’s high-level radioactive waste, represents one of the most extensively studied patches of real estate on the planet. Although the waste-disposal program was suspended in 2010, a large body of science provided unprecedented insights into the geologic, hydrologic, and climate histories and processes, and how these features contribute to a natural barrier for isolating hazardous wastes over geological time periods. One of the most critical mechanisms affecting repository performance is the flow of water through the 500- to 700-m-thick vadose zone, which has the potential to interact with waste packages and transport radionuclides to the accessible environment. In addition to understanding present-day conditions, reliable performance evaluations require knowledge of hydrologic responses to climate changes expected over a functional life span of more than 100,000 years for a repository.
Secondary hydrogenic minerals formed in this environment, mostly calcite and opal, contain physical, chemical, and isotopic information that can be used to decipher the history of past flow at various time scales. In addition, the mineral deposits allow the investigation of the mechanisms and processes of fracture flow, the source of the solutions, and the physical conditions under which the minerals formed. Information derived from these deposits represents an important means of evaluating hydrologic flow and transport models that are based largely on computer simulations of rock properties rather than direct observations.
The presentation will describe the general nature of the problem of understanding vadose flow through time as well as the evolution of how the mineral record was deciphered by scientists working on the Yucca Mountain Project at the USGS. Isotopic compositions of secondary calcite and opal confirm a meteoric source of infiltration and downward percolation that has remained more-or-less constant despite large variations in surface-water availability caused by fluctuations in Pleistocene climate. Those records reflect a substantial degree of hydrological stability which is likely to be maintained for hundreds of thousands of years or longer.
Biography: Jim Paces is a research geologist at the USGS who specializes in radiogenic isotope and geochronological studies. He received a Ph.D. degree from Michigan Technological University in 1988 that was focused on understanding the petrogenesis of flood basalts associated with the Proterozoic Midcontinent Rift. After completing a USGS-NRC postdoc working on lower crustal nodules from northern Michigan and mafic rocks of the Duluth Complex, he was hired by the Yucca Mountain Project Branch where he contributed to studies of paleoseismology, geomorphology, paleohydrology, and paleoclimate. After the Branch was disbanded in 2010, his focus has broadened to include areas outside of southern Nevada and his current work includes geochemical and isotope studies of speleothems, peat-rich wetland deposits, archeological materials, calcic soils, ground -water discharge deposits, and hydrologic flow systems.
Regional Analysis of Flood Hazards Along the Colorado Front Range
by John Pitlick, Profesor of Geography, University of Colorado, Boulder
Abstract: The hazards associated with rare but intense rainfall are well known in Colorado, and many communi-ties along the Front Range have taken action over the years to mitigate potential damage and loss of life from rare floods. In September 2013, we had the opportunity to observe firsthand what it is like to get half a years-worth of precipitation in one or two days, and we can begin to appreciate how the actions taken to reduce flood risks in the city of Boulder benefited the community as a whole. Nonetheless many questions have arisen in the aftermath of the 2013 flood. For example, media reports have sug-gested that this was a 100-yr flood. What is the basis for that estimate? How do published maps of in-undation for floods with different return periods compare with the extent of flooding in 2013? Did burned areas contribute disproportionately to the floods? We don’t have complete answers to all these questions just yet, thus my goal in this talk is to share results from past work (my own, plus others) that will help put the September 2013 floods in perspective.
Biography: John Pitlick’s research focuses on linkages between surface-water hydrology and geomorphology in high-gradient river systems. The primary objective of this work is to develop a more complete un-derstanding of the coupling between rivers and their surrounding landscapes. Field work is an im-portant component of his research; the strategy used in many projects is to integrate field data with modeling techniques to quantify the effects of sediment transport on the natural functioning of river systems, often at spatial scales >100 km. Several past projects, done in collaboration with aquatic ecologists, have focused on the role of fluvial-hydraulic processes in modifying habitats for fish and benthic organisms. Dr. Pitlick has worked extensively in Colorado and also in the Pacific Northwest and the northern Rocky Mountains. He is co-director of the Graduate Program in Hydro-logic Sciences at CU-Boulder. John received his Ph.D. from Colorado State University in 1988.
The Mid-Wisconsin Human Colonization of North America:
A Call for Archaeological Investigations in Older Geological Deposits
by Steven R. Holen and Kathleen Holen, Center for American Paleolithic Research, Fort Collins, CO
Abstract: The hypothesis that humans entered North America during the mid-Wisconsin via Beringia was proposed by Muller-Beck in the 1960s. The Mammoth Steppe Hypothesis presented here suggests that humans entered North America from Siberia during the relatively warm mid- Wisconsin, 40,000 to 22,000 rcybp. A mammoth steppe biome extended from Europe across Siberia to Alaska, and in modified form, into the Great Plains of North America. The authors offer evidence of a mid-Wisconsin human presence in the North American mid-continent, including Colorado. The hypothesis that Upper Paleolithic populations successfully adapted to the mammoth steppe biome and entered mid-continent North America before the Last Glacial Maximum ice sheet covered Canada is supported with enough evidence to justify further research. We suggest that it is important for archaeologists to investigate older geological deposits in their search for archaeological components and to educate and collaborate with paleontologists who do work in these deposits.
Biographies: Steven Holen has more than 40 years of archaeological experience in the Great Plains and has worked on all types of archaeological sites dating from historic to pre-Clovis. Recently, Steve has concentrated his efforts on determining when humans first arrived in North America. He has excavated several mammoth sites with impact-fractured and flaked bone that suggest humans were present on the Great Plains during the Last Glacial Maximum when Canada was covered with glaciers from coast to coast. This evidence indicates that humans must have arrived before the route from Siberia to the Great Plains was closed about 22,000 years ago. Steve also researches Clovis lithic procurement and mobility on the Central Plains. Steve recently retired as Curator of Archaeology at the Denver Museum of Nature & Science. He then joined his wife Kathleen in a new nonprofit organization, the Center for American Paleolithic Research, with the goal of searching for evidence of early humans in the Americas.
Kathleen Holen retired as a Geriatric Nurse Practitioner after more than 26 years in practice and more than 10 years of avocational archaeology. In 2009 she received her MA in archaeology from the University of Exeter, Devon, United Kingdom. She is interested in early human dispersals into the Americas from the perspective of human cognition and behavior. She has participated in Steven Holen’s research by studying prey animal bones and methods for differentiating human made bone modifications from other causes. She is co-director of the Center for American Paleolithic Research.
In the Footsteps of the Early Bone Diggers:
Locating Historic Photographic Sites in the Bridger Basin of Southwest Wyoming
by Emmett Evanoff, University of Northern Colorado
Abstract: The early paleontologists and geologists of the late 1800s and early 1900s did not have detailed topographic maps or aerial photographs to locate their fossil localities. However, they did employ photographers to take im-ages of the intricately eroded badlands in which their fossils occurred. The earliest of these photographs (taken between 1868 and 1870) were to provide Congress and the public a visual record of the bizarre erosional fea-tures of the badlands. The photographs supplemented the geologic survey’s annual reports so that Congress would grant their yearly funding. By the earliest twentieth century, scenic photographs started to take a second-ary role to documenting fossil localities. These photographs now provide not only a historical record of the early surveys; they also provide the only record of the precise locations of important fossil localities, many of which were type localities of important fossil vertebrates and invertebrates.
The historic photographs of the Bridger Basin that we have been studying are available from websites of the archives of the U.S. Geological Survey and the American Museum of Natural History. We have downloaded and printed copies of the historic images, and taken these images into the field. Two decades of geologic study in the Bridger Basin by Evanoff and colleague Paul Murphey allows us to identify the general location of most of the photographs. We hike to areas where the images were taken where we match as closely as we can the background and foreground features on the images to features seen in the field. We then take digital images of the same view of the original photograph, determine its position on a topographic map and by GPS coordinates, take directional azimuths of features in the background (using a Brunton compass), and record the time and date of the repeat photograph. To date, we have relocated 32 historic photograph sites. Finding a photo site is an exciting experience, knowing that you are standing at the same place as the famed early photographer Wil-liam H. Jackson or the famous paleontologist Walter Granger stood over a century ago.
The earliest photograph in the Bridger Basin is one of Church Butte that was taken by A.J. Russell in 1868 that shows the edge of the Oregon-California-Mormon Trail and the first transcontinental telegraph line. William H. Jackson in 1870 took a series of photographs of the badlands at and near Church Butte, while he was travelling with the Hayden geologic survey. These photographs document Hayden’s men collecting verte-brate fossils in the badlands, some of which became the type specimens for a number of fossil mammals. The American Museum of Natural History in New York made a paleontologic survey of the Bridger Basin between 1903 and 1905. The photographs of this survey were taken by Albert Thomson and Walter Granger. These photos include panoramas of badlands, fossil localities, local ranches, and campsites. The reimaging of these historic photographic sites reveals details of the erosion of the outcrops and changes in vegetation over the past century.
Biography: Emmett Evanoff is an Associate Professor at the University of Northern Colorado, De-partment of Earth and Atmospheric Sciences, as well as a research associate at the University of Colorado Museum in Boulder and the Denver Museum of Nature and Sci-ence. He has extensively studied the middle Cenozoic sedimentary rocks of the Great Plains and Rocky Mountains. His specialty is the stratigraphy, sedimentology, and paleontology of distal volcaniclastic sequences such as the White River Group and the Bridger Formation. Professor Evanoff has worked for over a decade in Badlands Na-tional Park in South Dakota, as well as on the deposits of Florissant Fossil Beds Na-tional Monument. He has a broad range of interests ranging from Cenozoic terrestrial land snail and vertebrate faunas, to the distribution and origin of Cenozoic volcanic ash deposits, to the changes of Rocky Mountain and Great Plains landscapes during the Cenozoic, to the history of geological studies in the Rocky Mountains and Great Plains. He is a past-president of the Colorado Scientific Society, and has helped organize two symposia for CSS. He has also been active in pre-senting talks and organizing topic sessions for the Geological Society of America, the Society of Vertebrate Paleon-tologists, and the Western Interior Paleontological Society. He received his Ph.D. in 1990 at the University of Colora-do, Boulder.
Student Night Participants and Presentations
Comparison of Economic Risk from Post-Wildfire Debris Flows at Three Sites in the Western United States
Kevin McCoy, Department of Geology and Geological Engineering, Colorado School of Mines
Changes in Morphology In and Around the North St. Vrain River Due to the September, 2013 Flood
Linda Glickstein, Department of Earth Sciences, University of Northern Colorado
A Landslide Risk Evaluation and Reduction Matrix for Lower Income Communities in Guatemala City
Ethan J. Faber, Department of Geology and Geological Engineering, Colorado School of Mines
Lava Lake Thermal Pattern Classification Using Self-Organizing Maps and Relationships to Eruption Processes at Kilauea Volcano, Hawaii
Amy M. Burzynski, Department of Earth Sciences, University of Northern Colorado
Geology of the North Amethyst Au-Ag Epithermal Deposit, Creede District, Colorado
Mario Guzman, Department of Geology and Geological Engineering, Colorado School of Mines,
Using Geochemical Indicators to Distinguish High Biogeochemical Activity in Sediments
Amy M. Kenwell, Department of Geology and Geological Engineering, Colorado School of Mines
20 Years After: A Brief Update on the Study of Telluride Minerals and Deposits
by Dr. Bruce Geller, Director of the Colorado School of Mines Museum
Much research has been conducted on telluride deposits (those containing the element Te), applying new tools and insights, in the twenty years since the completion of my doctoral studies (Geller, 1993). Telluride has become a more sought-after commodity, since its application in modern photovoltaic (PV) cells, thermoelectric devices (in military and medical applications), certain memory chips, and guided missiles (George, 2013a). Twenty years ago, telluride was only employed in industrial applications, such as metal alloying, rubber vulcanization, and in glass/ceramic pigments, but continues to be used in these industries today (George, 2013b). It is likely that demand for telluride will grow, as technology advances, catalyzing better understanding of telluride mineral distribution, exploration for more telluride deposits, and improved methods of telluride extraction. All telluride produced until re-cently, came as a by-product from processing sulfide ores. Only one deposit in China has recently been mined specifically for its telluride.
Although telluride remains one of the rarest elements on earth, the IMA has approved 85 un-oxidized telluride minerals (those lack-ing O in their formulae). These are found in diverse geologic environments, generally in the trigonal crystal system. Despite similar chemical behavior with selenium, only about 9% of worldwide telluride deposits have any reported selenium species (Ralph, 2014). Literature reported correlations of tellurides with vanadium minerals are also over-exaggerated and run only at about 6% (Ibid). Nineteen elements have been found to bond with telluride in nature, the most common being bismuth, sulfur, and silver. There is no known natural Cd telluride phase. Ralph (2014) reports that the six most typically occurring tellurides on earth (referred to in this talk as ‘the big six’) in order of occurrences are: hessite, tetradymite, altaite, petzite, sylvanite, and calaverite, which strongly cor-roborates data presented in my dissertation, but not entirely in that order.
Tellurides have been reported on six continents. From data in Ralph (2014), many countries now report tellurides that did not in 1993. China has seen the largest increase in the number of telluride deposits. In 1993, the Boulder Telluride Belt (BTB) in Colorado had the largest diversity of telluride minerals in the geologic literature. Today, eight districts on four continents eclipse the BTB in this distinction (cover photo).
The countries with the most telluride occurrences as reported by Ralph (2014) are: the United States, China, Canada, and Russia, which correlates well with their overall land size. Colorado had the most telluride occurrences per square kilometer of any region in the U.S. in 1993 (Geller, 1993). Extrapolating from data presented by Ralph (2014), Colorado presently has the most telluride oc-currences per square kilometer of any known region in the world, statistically.
In the future, more tellurides will be discovered, from more worldwide occurrences, from type localities and occurrences with ex-tremely diverse telluride mineralogy, but they will remain rare, occur in trace amounts, and probably possess similarities to “typical” telluride chemistry (the predominance of Bi, S, Ag, Pb, Pd, Cu, Au, etc.). The ‘big six’ will continue to dominate world occurrences. This study corroborates the value of mineral databases in mineral research.
Geller, Bruce Alan, 1993, Mineralogy and origin of telluride deposits in Boulder County, Colorado, Univ. of Colorado at Boulder Ph.D. dissertation, 731p.
George, M.W., 2013a. “Mineral resource of the month, Tellurium.” Earth Magazine. March 2013, p.57.
George, M.W., 2013b, “Tellurium,” Mineral Commodity Summaries, U.S. Geological Survey, January 2013, http://minerals.usgs.gov/minerals/pubs/commodity/selenium/mcs-2013-tellu.pdf.
Ralph, J. (2014). Retrieved from http://www.mindat.org/
Continental glaciation: some remarkable impacts on the geomorphic and geologic record; CSS President’s Address
by Scott Lundstrom, U.S. Geological Survey, 2014 CSS President
Abstract: Glaciation has produced significant effects in the geologic record and has left a remarkable, extensive, and varied legacy on landscapes of North America and other glaciated regions. Largely since the mid-19th century, the geologic and geomorphic effects of Pleistocene ice ages have been readily recognized and extensively studied, but basic aspects of the glacial geologic record remain yet to be well-understood. Such aspects thus represent an important scientific frontier to the extent that improved understanding could potentially lead to better predictive capabilities. Major glacial intervals recognized in the Cenozoic, Paleozoic (Gondwanaland glaciations), Late Proterozoic (Cryogenian), and early Proterozoic (and possibly Archaean) are known to have profoundly affected sea-level (eustatic, isostatic, and other effects on the geoid), ocean chemistry, sequence stratigraphy, biologic evolution, paleoenvironments and mineral resources. In this address, I will discuss some enigmatic geomorphic and stratigraphic aspects of the late Pleistocene glacial geologic record from the Great Lakes and Great Plains regions.
Tunnel valley networks and subglacial flow-field bedforms, including drumlin/flute fields, form common and overlapping elements within landscape records of deglaciated Pleistocene ice sheets, yet the origins of these landforms and associated glacial geologic frameworks are not well understood. Analysis of geologic maps, subsurface framework, and surface morphology from North American glacial records show relations between forms and geology that (along with geophysics and continuity) constrain processes relevant to the subglacial origin of these features. For example, the morphologically concordant occurrence of bedrock-cored drumlins within drumlin fields provides evidence that subglacial erosional processes are necessary to their development. Aligned with similar orientations as bedrock-cored forms, drumlins and fluted forms with cores of unconsolidated sediment are a combination of erosional remnants of preexisting substrate (similar to bedrock cores) and later secondary accretionary mantle. Such a mantle is not essential to the drumlin form, but was accreted from debris-rich basal ice and/or advected subglacial sediment after the erosion of the swales that surround and created the core of the drumlins. In many areas, inter-drumlin networks of swales have a more deeply incised tunnel valley network superimposed upon them. Morphologic relations provide evidence that tunnel valley formation occurred during relatively late stages of glaciations and after drumlin formation. Drumlin form and dimensions generally do not vary in relation to proximity to tunnel valley margins, except for individual drumlins that adjoin and appear to be truncated at the margins of larger tunnel valleys. These relations indicate a transformation of erosional subglacial hydraulic conditions from a partially but not entirely distributed system (possibly linked cavity; but not sheetflow) to a more channelized regime of the tunnel valley network. Such relations are common within large areas beneath the southern sector of the Laurentide ice sheet, especially within the Great Lakes region, and exemplified by the glaciated landscape of the Grand Traverse Bay region, Michigan.
Along the glaciated areas and margins of the Great Plains, we have morphologically contrasting records produced during late Pleistocene timing that overlaps that of the Great Lake region. One notable example is that of the latest Pleistocene record of the James lobe of South Dakota. Here, the late Pleistocene Laurentide ice sheet advanced southward across eastern South Dakota to within 6 km of its maximum Wisconsin extent along the modern Missouri River valley. This significant glacial advance occurred during latest Pleistocene time of the latter part of the Bølling/Allerød interstadial warm period. Maximum ages on the southward advance of at least 160 km are on 14C dates (12,880 – 12,050 14C yrs BP; ~14.5 ka cal) on wood that was deeply buried (up to 58 m) by late Wisconsin glacial deposits (mainly till). These dates are from 12 sites in 10 counties, and are consistent with paleoecologic studies that indicate that spruce parkland occupied the region that was partially overridden by the glacial advance. Close minimum ages on the glacial advance are provided by 230Th/U dates ranging from 13.02 + 0.23 to 10.48 + 0.57 on travertine laminae of groundwater discharge deposits that overlie the glacial deposits; as well as ages on younger Laurentide moraines of readvances to positions 300 km to the northeast and that preceded Lake Agassiz. Consistent with geochronology, loess cover is largely absent to very thin on till surfaces in the James River lowland except for areas near postglacial sources such as the Missouri River valley. The sparsity of loess contrasts with thick loess mantles in adjacent glaciated areas of southeastmost SD, eastern Nebraska, and northwest Iowa. The 14C dates span the Bølling time interval that ice core records show was markedly warmer than preceding glacial conditions. Thus, the late Wisconsin readvance of the James lobe, and similarly timing of readvances of the Des Moines and Lake Michigan lobes, may be complex dynamic responses of the Laurentide ice sheet to climatic warming, and increased meltwater production.
Though located outside of the footprint of the Laurentide ice sheet, the nonglaciated river systems of the Great Plains have been markedly influenced by continental glaciation through controls on base level, as exemplified by the late Quaternary geomorphic history of the Niobrara River.