GSA Today最新文献

{"title":"Supplemental Material: A Boost for the CURE: Improving Learning Outcomes with Curriculum-Based Undergraduate Research","authors":"Joseph L. Allen, Stephen Kuehn, E. Creamer","doi":"10.1130/gsat.s.12290381.v2","DOIUrl":"https://doi.org/10.1130/gsat.s.12290381.v2","url":null,"abstract":"MS-CURE research activities, learning goals, and rubric for student assessment","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141205361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A Guide to Graduate School Admissions in the Geosciences","authors":"S. Smidt, D. Gates","doi":"10.1130/gsatg410gw.1","DOIUrl":"https://doi.org/10.1130/gsatg410gw.1","url":null,"abstract":"","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43674234","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Remnants and Rates of Metamorphic Decarbonation in Continental Arcs","authors":"E. Ramos, J. Lackey, J. Barnes, A. Fulton","doi":"10.1130/gsatg432a.1","DOIUrl":"https://doi.org/10.1130/gsatg432a.1","url":null,"abstract":"Metamorphic decarbonation in magmatic arcs remains a challenge to impose in models of the geologic carbon cycle. Crustal reservoirs and metamorphic fluxes of carbon vary with depth in the crust, rock types and their stratigraphic succession, and through geologic time. When byproducts of metamorphic decarbonation (e.g., skarns) are exposed at Earth’s surface, they reveal a record of reactive transport of carbon dioxide (CO2). In this paper, we discuss the different modes of metamorphic decarbonation at multiple spatial and temporal scales and exemplify them through roof pendants of the Sierra Nevada batholith. We emphasize the utility of analogue models for metamorphic decarbonation to generate a range of decarbonation f luxes throughout the Cretaceous. Our model predicts that metamorphic CO2 fluxes from continental arcs during the Cretaceous were at least 2 times greater than the present cumulative CO2 flux from volcanoes, agreeing with previous estimates and further suggesting that metamorphic decarbonation was a principal driver of the Cretaceous hothouse climate. We lastly argue that our modeling framework can be used to quantify decarbonation fluxes throughout the Phanerozoic and thereby refine Earth systems models for paleoclimate reconstruction.","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-05-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42060921","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Individual Development Plans (IDPs): An Underutilized Advising Tool in the Geosciences","authors":"D. Eason, B. C. Bruno, Daniela Bottjer-Wilson","doi":"10.1130/gsat.s.12130890.v2","DOIUrl":"https://doi.org/10.1130/gsat.s.12130890.v2","url":null,"abstract":"Additional program information and implementation details, advisor/mentor survey results, and a copy of the basic IDP template used in the ‘Ike Wai project.","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-04-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42026860","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"¡Cuba! River Water Chemistry Reveals Rapid Chemical Weathering, the Echo of Uplift, and the Promise of More Sustainable Agriculture","authors":"P. Bierman, R. Y. S. Hernández, A. Schmidt, H. C. Aguila, Yoelvis Bolaños Alvarez, Aniel Guillén Arruebarrena, M. K. Campbell, D. Dethier, M. Dix, M. Massey-Bierman, A. Moya, J. Perdrial, J. Racela, C. Alonso-Hernández","doi":"10.1130/gsatg419a.1","DOIUrl":"https://doi.org/10.1130/gsatg419a.1","url":null,"abstract":"For the first time in more than half a century, a joint Cuban/American science team has worked together to quantify the impacts of chemical weathering and sustainable agriculture on river water quality in Cuba—the largest and most populous Caribbean island. Such data are critical as the world strives to meet sustainable development goals and for understanding rates of landscape change in the tropics, an understudied region. To characterize the landscape, we collected and analyzed water samples from 25 rivers in central Cuba where upstream land use varies from forested to agricultural. Cuban river waters bear the fingerprint of the diverse rock types underlying the island, and many carry exceptionally high dissolved loads. Chemical denudation rates are mostly among the top 25% globally and are similar to those measured in other Caribbean islands. High rates of solute export and the distinct composition of the waters in specific basins suggest flow paths that bring river source waters into contact with fresh, weatherable rock—unusual in a warm, wet, tropical climate where weathering should extend deep below the surface. Tectonically driven uplift likely maintains the supply of weatherable material, leading to channel incision and, thus, to the exposure of bedrock in many river channels. Despite centuries of agriculture, the impact on these rivers’ biogeochemistry is limited. Although river water in many central Cuban rivers has high levels of E. coli bacteria, likely sourced from livestock, concentrations of dissolved nitrogen are far lower than other areas where intensive agriculture is practiced, such as the Mississippi River Basin. This suggests the benefits of Cuba’s shift to conservation agriculture after 1990 and provides a model for more sustainable agriculture worldwide. INTRODUCTION The Republic of Cuba (Fig. 1) has more than 11 million inhabitants, but there has been little collaboration between U.S. and Cuban scientists for more than half a century although only 160 km separates the two countries (Feder, 2018). River biogeochemistry data, which are sparse in tropical regions, are needed to guide sustainable development in Cuba and, by example, in other tropical and island nations. Here, we present and interpret extensive new data characterizing river waters in central Cuba, the result of a bi-national, collaborative field campaign. Biogeochemical analyses allow us to address fundamental geologic questions, such as the pace of chemical weathering in the tropics, as well as applied environmental questions related to the quality of river water and human impacts on a landscape where small-scale, sustainable farming has replaced substantial swaths of industrial agriculture (The Guardian, 2017). BACKGROUND AND METHODS Cuba’s wet, warm tropical landscape is dominated by mountains (up to 1917 m above sea level [asl] in the east, 500–700 m asl elsewhere) running parallel to the north and south coasts (Fig. 1). Mainly forested uplands descend into","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46628841","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Decoupling Process from Form in Landscape Evolution Studies","authors":"D. Hedding","doi":"10.1130/gsatg422c.1","DOIUrl":"https://doi.org/10.1130/gsatg422c.1","url":null,"abstract":"According to Cruden (2003), the term “landslide” was first recorded in 1838 by J.D. Dana. Varnes (1958) used “landslide” in the title of his well-known paper but subsequently abandoned the term in favor of “slope” in the updated iteration (see Varnes, 1978). Varnes (1978, p. 11) states that the reason for the change is that “improvements in technical communication require a deliberate and sustained effort to increase the precision associated with the meaning of words, and therefore the term slide will not be used to refer to movements that do not include sliding.” Later, Cruden (1991, p. 28) suggested that a landslide is “the movement of a mass of rock, earth or debris down a slope” and is intended for informal, non-technical use. Several other definitions have been suggested; however, Shanmugam (2015) notes that the term “landslide” lacks conceptual clarity. Nevertheless, the term “landslide” remains entrenched in the literature and, with each scientific discipline using its own nomenclatural scheme, it means different things to different groups (Shanmugam, 2015). In the study of landscape evolution, the transfer of considerable volumes of material downslope under the influence of gravity plays a significant role in shaping landscapes (Cendrero and Dramis, 1996). As such, various papers assess the role and significance of slope processes and resultant mass movements in landscape evolution, typically within the context of quantifying erosion rates (Roda-Boluda et al., 2019) and/ or the roles of tectonic and climatic factors in weathering (Emberson et al., 2016). Often the terms “landsliding” or “bedrock landsliding” are used to describe the process by which material moves downslope (Egholm et al., 2013; Roering et al., 2001, 2005). However, their usage demonstrates a poor appreciation of the difference between process and form in geomorphology since these terms are intrinsically linked to landslides that are a discrete geomorphological landform and not to the range of process(es) that are responsible for the movement of material downslope in landscape evolution. In addition, form-convergence (equifinality) suggests that morphologically similar landforms can be generated by different processes, on their own or in combination, which complicates the correct identification of the process-origin of landforms (Hedding, 2016; Hedding et al., 2018). Still, the term “landsliding” is often described as the process responsible for the movement of material downslope and has received a level of credence (see Roering et al., 2001) through repetition and subsequent acceptance in the literature, rather than recognition of the actual process-form relationships. Notwithstanding the poor phrasing, the term “landsliding” is sometimes used as a synonym for “mass wasting.” However, the movement of material downslope in landscape evolution can be generated through a suite of mass wasting (movement) processes resulting in landforms (e.g., catastrophic mudflows and rockf","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46372245","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THOMPSON FIELD FORUM REPORT: Age and Carving of Grand Canyon: Toward a Resolution of 150 Years of Debate","authors":"K. Karlstrom, L. Crossey, E. Humphreys, D. Shuster, K. Whipple, R. Crow","doi":"10.1130/gsat-tff-gc.1","DOIUrl":"https://doi.org/10.1130/gsat-tff-gc.1","url":null,"abstract":"The age and evolution of the Grand Canyon, in the western USA, have been debated since J.W. Powell’s exploration of the Colorado River in 1869. This paper reports results of a 2019 GSA Thompson Field Forum that honored the 150th anniversary of Powell’s first trip. INTRODUCTION The 2019 GSA Thompson Field Forum, “Age and Carving of Grand Canyon: Toward a Resolution of 150 Years of Debate” involved 28 researchers and young scientists (Table 1) who discussed the evidence for the age, geomorphic evolution, and incision history of Grand Canyon in the context of recent advances and ongoing debates. The objective was to emphasize the power of","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43171555","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Future for Geoscience in the Context of Emerging Climate Disruption","authors":"D. Siegel","doi":"10.1130/gsat19prsadrs.1","DOIUrl":"https://doi.org/10.1130/gsat19prsadrs.1","url":null,"abstract":"","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47669150","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Faint Young Sun Problem Revisited","authors":"J. E. Spencer","doi":"10.1130/GSATG403A.1","DOIUrl":"https://doi.org/10.1130/GSATG403A.1","url":null,"abstract":"Earth and Mars should have been frozen worlds in their early history because of lower solar luminosity but were not, which challenges our understanding of early atmospheres and surface conditions and/or our understanding of solar evolution. This is known as the “faint young Sun problem.” One resolution to the problem is that the Sun was more massive and luminous in its youth before blowing off mass. Astrophysical studies of stellar evolution and behavior, however, including recent analysis of Kepler space-telescope data, indicate that mass loss is both insufficient and occurs too early to allow for a more luminous Sun after ca. 4 Ga. Alternatively, greenhouse gases were surprisingly effective at warming young Earth and Mars. High concentrations of CO2 with the possible addition of biogenic CH4 are likely dominant factors promoting open-water conditions on Archean Earth. Evidence of precipitation and flowing water on young Mars, including river valleys thousands of kilometers long, is more problematic. Recent studies indicate that 3–4 Ga river valleys and delta deposits in crater lakes could have been produced in <~107 years. Highly transient warm periods during times of favorable orbital parameters possibly led to brief melting under otherwise icy conditions. Seasonal melting and runoff would be more likely with ~1%–10% atmospheric H2 and CH4, perhaps derived from serpentinization of olivine in the martian crust and released from frozen ground by impacts and volcanism, and/or derived directly from volcanic outgassing. The recently recognized effectiveness of hydrogen and methane at absorbing infrared radiation in a thick CO2-dominated atmosphere, in a process known as “collision-induced absorption,” is probably essential to the solution to the faint young Sun problem for Mars. INTRODUCTION The basic concepts involved in stellarenergy generation were known by the 1950s and include the insight that stellar luminosity gradually increases over time because of increasing density in stellar cores resulting directly from thermonuclear fusion (e.g., Burbidge et al., 1957) (Fig. 1). Solar luminosity at birth was calculated to be ~70% of modern luminosity. The idea that Earth should have geologic evidence of its presumably frozen youth was gradually determined to be inconsistent with growing evidence for liquid water at the surface of Archean Earth. The problem was first addressed by Sagan and Mullen (1972), who proposed that atmospheric ammonia was crucial to early warming. More recent robotic exploration of Mars similarly indicates surprisingly warm and wet conditions during its early geologic history. The discrepancy between low solar-energy production and warm early Earth and Mars is known as the “faint young Sun problem” (Ulrich, 1975; Feulner, 2012). This article is a brief review of solar evolution and the faint young Sun problem for Earth and Mars that highlights recent developments. STELLAR ENERGY PRODUCTION Stars form by gravitational contraction","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43586585","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Subduction Polarity in Ancient Arcs: A Call to Integrate Geology and Geophysics to Decipher the Mesozoic Tectonic History of the Northern Cordillera of North America","authors":"T. Pavlis, J. Amato, J. Trop, K. Ridgway, S. Roeske, G. Gehrels","doi":"10.1130/GSATG402A.1","DOIUrl":"https://doi.org/10.1130/GSATG402A.1","url":null,"abstract":"Terry L. Pavlis, Dept. of Geological Sciences, University of Texas, El Paso, Texas 79968, USA; Jeffrey M. Amato, Dept. of Geological Sciences, New Mexico State University, Las Cruces, New Mexico 88003, USA; Jeffrey M. Trop, Dept. of Geology and Environmental Geosciences, Bucknell University, Lewisburg, Pennsylvania 17837, USA; Kenneth D. Ridgway, Dept. of Earth, Atmospheric and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA; Sarah M. Roeske, Earth and Planetary Sciences Dept., University of California, Davis, California 95616, USA; and George E. Gehrels, Dept. of Geosciences, University of Arizona, Tucson, Arizona, 85721, USA","PeriodicalId":35784,"journal":{"name":"GSA Today","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41872208","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}