GSA Today最新文献_第7页

Supplemental Material: A Boost for the CURE: Improving Learning Outcomes with Curriculum-Based Undergraduate Research 补充材料：为 CURE 助力：通过基于课程的本科生研究提高学习成果

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-05-12 DOI: 10.1130/gsat.s.12290381.v2

Joseph L. Allen, Stephen Kuehn, E. Creamer

MS-CURE research activities, learning goals, and rubric for student assessment

MS-CURE 研究活动、学习目标和学生评估标准

引用次数: 1

A Guide to Graduate School Admissions in the Geosciences 《地球科学研究生入学指南》

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-05-01 DOI: 10.1130/gsatg410gw.1

S. Smidt, D. Gates

引用次数: 0

Remnants and Rates of Metamorphic Decarbonation in Continental Arcs 大陆弧变质脱碳的残余物和速率

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-05-01 DOI: 10.1130/gsatg432a.1

E. Ramos, J. Lackey, J. Barnes, A. Fulton

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.

岩浆弧中的变质脱碳作用仍然是地质碳循环模型中的一个挑战。地壳储层和变质碳通量随地壳深度、岩石类型及其地层演替以及地质年代而变化。当变质脱碳的副产物(如夕卡岩)暴露在地球表面时，它们揭示了二氧化碳(CO2)反应性运输的记录。本文讨论了不同时空尺度的变质脱碳模式，并通过内华达山脉岩基顶板垂坠进行了举例说明。我们强调利用变质脱碳模拟模型来生成整个白垩纪的一系列脱碳通量。我们的模型预测，白垩纪时期大陆弧的变质二氧化碳通量至少是目前火山累积二氧化碳通量的2倍，与先前的估计一致，并进一步表明变质脱碳是白垩纪温室气候的主要驱动因素。我们最后认为，我们的建模框架可以用来量化整个显生宙的脱碳通量，从而改进古气候重建的地球系统模型。

{"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":"30 1","pages":"4-10"},"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}

引用次数: 6

Individual Development Plans (IDPs): An Underutilized Advising Tool in the Geosciences 个人发展计划：地球科学中一个未被充分利用的咨询工具

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-04-15 DOI: 10.1130/gsat.s.12130890.v2

D. Eason, B. C. Bruno, Daniela Bottjer-Wilson

Additional program information and implementation details, advisor/mentor survey results, and a copy of the basic IDP template used in the ‘Ike Wai project.

其他项目信息和实施细节，顾问/导师调查结果，以及“艾克围”项目中使用的基本国内流离失所者模板的副本。

引用次数: 1

¡Cuba! River Water Chemistry Reveals Rapid Chemical Weathering, the Echo of Uplift, and the Promise of More Sustainable Agriculture ¡古巴！河水化学揭示了快速的化学风化、上升的回声和更可持续农业的前景

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-03-01 DOI: 10.1130/gsatg419a.1

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

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

半个多世纪以来，古巴/美国的一个联合科学团队首次合作，量化化学风化和可持续农业对古巴河流水质的影响。古巴是加勒比最大、人口最多的岛屿。在世界努力实现可持续发展目标和了解热带地区（一个研究不足的地区）景观变化率的过程中，这些数据至关重要。为了描述景观特征，我们收集并分析了古巴中部25条河流的水样，这些河流的上游土地利用从森林到农业各不相同。古巴河水具有岛下不同岩石类型的特征，许多河水的溶解负荷异常高。化学剥蚀率大多在全球前25%，与其他加勒比岛屿的测量结果相似。特定盆地中的高溶质输出率和独特的水成分表明，河流源水与新鲜的、可风化的岩石接触的流动路径——这在温暖、潮湿的热带气候中是不寻常的，因为风化应深入地表以下。构造驱动的隆起可能维持了可风化材料的供应，导致河道切开，从而暴露出许多河道中的基岩。尽管有几个世纪的农业，但对这些河流的生物地球化学影响是有限的。尽管古巴中部许多河流的河水中大肠杆菌含量很高，很可能来自牲畜，但溶解氮的浓度远低于其他实行集约农业的地区，如密西西比河流域。这表明古巴在1990年后转向保护性农业的好处，并为全世界更可持续的农业提供了一个模式。引言古巴共和国（图1）有1100多万居民，但半个多世纪以来，美国和古巴科学家之间几乎没有合作，尽管两国相距仅160公里（Feder，2018）。河流生物地球化学数据在热带地区稀少，需要这些数据来指导古巴的可持续发展，例如其他热带和岛屿国家的可持续发展。在这里，我们介绍并解释了古巴中部河水的大量新数据，这些数据是两国合作实地活动的结果。生物地球化学分析使我们能够解决基本的地质问题，如热带地区化学风化的速度，以及与河水质量和人类对小规模可持续农业取代大片工业化农业的景观影响有关的应用环境问题（《卫报》，2017）。背景和方法古巴潮湿温暖的热带景观主要是与南北海岸平行的山脉（东部海拔1917米，其他地方海拔500–700米）（图1）。主要是森林覆盖的高地下降到耕种的起伏平原和红树林成荫的低洼沿海河口。夏季气候潮湿，“古巴！河水化学揭示了快速的化学风化、隆起的回声和更可持续农业的前景，https://doi.org/10.1130/GSATG419A.1.版权所有2020，美国地质学会。CC-BY-NC。图1。古巴，高程为渐变色。黑色轮廓是图3中绘制的区域。插图显示了古巴相对于北美的位置。4今日GSA | 2020年3月至4月冬季干旱，信风阵雨和较大热带风暴带来降水。古巴地质的多样性反映了其位于北美和加勒比板块边界的构造环境。古巴中部基底岩性包括增生火成岩、沿被动边缘形成的沉积物（碎屑岩、碳酸盐岩和蒸发岩）、凸起蛇绿岩和岛弧岩（Iturralde Vinent et al.，2016）。该基底被轻微变形的年轻海洋和陆地沉积岩不整合覆盖（IturraldVinent，1994）。在河水与这些不同岩石相互作用的地方，地表水化学成分应反映下伏岩石单元的组成。古巴实行农业已有几个世纪了。土著人种植木薯、丝兰和玉米（Cosculluela，1946）。1492年开始的西班牙殖民带来了奴隶、大规模的糖农业和养牛业（Zepeda，2003）。1898年古巴从西班牙独立后，在美国的影响下，古巴的食糖产量翻了两番（Whitbeck，1922）。1959年古巴与苏联结盟时，糖业工业化以提高产量和出口成为中心目标（Pérez-López，1989）。到20世纪80年代，古巴拥有拉丁美洲机械化程度最高的农业部门（FeblesGonzález et al。，2011）；然而，1991年苏联解体促使古巴采取了减少耕作、有机土壤改良、使用覆盖作物以及用驯养的牲畜（包括马和牛）取代燃料匮乏的拖拉机（Gersper等人，1993年）。古巴中部的地表水生物地球化学监测主要集中在水库上。在古巴中部，来自四个水库的水化学数据（1986–2005）表明，主要离子浓度的主要控制因素是上游的岩石风化，这四个水库代表了两个水系和四个地质不同的盆地（Betancourt et al.，2012）；四个流域中有三个流域的水化学在旱季和雨季之间没有统计学上的显著差异。2018年8月（雨季），我们从古巴中部的25个流域采集了水样。我们选择这些地点是为了涵盖一系列土地用途、下游岩石类型、流量和流域大小，同时避开有大型水坝的河流（图2和3N）。有关详细方法，请参阅GSA数据存储库1。我们的分析假设我们测量的阳离子和阴离子浓度代表年平均值（Godsey等人，2009）。结果古巴中部的河水样本含有高浓度的溶解物质（图3和图4）。电导率和总溶解负荷较高（分别为130-1380μS/cm和117-780 mg/L，见表S1和S2[见脚注1]）；除了从森林集水区取样的河水外，河水都是浑浊的。样品pH接近中性至微碱性，碳酸氢盐碱度较高（65–400 mg/L）。As、Ba、Cr、Mn、Ni、Sr和U存在于我们分析的部分或全部古巴河水中，在所有情况下都低于饮用水标准（表S3[见脚注1]）。现场测量的溶解氧含量在59%至145%之间（平均97%）。利用特定流域的降水量（图3），以及径流估计值（Beck等人，20152017）和每个古巴水样的总溶解固体（TDS），我们估计了42至302 t km–2 y–1之间的化学风化率，平均值为161±66 t km–1。溶解有机碳（DOC）变化很大，范围从Cl>SO4>NO3>HPO4>NO2>Br>F。在现场（0.1–0.8 mg/L）和实验室（0.4–0.5 mg/L）测量阴离子正磷酸盐（as P）；现场分析和实验室分析呈正相关。阳离子的平均减少顺序为Ca>Na>Mg>Si>K.在所有样本中都发现了大肠杆菌，根据世界卫生组织的标准，大多数样本（20/24）含有足够的细菌，被认为不安全，不适合娱乐使用（最可能数（MPN）>127/100 ml）。MPN/100ml>1000的两个样品（CU-107和110）的遗传微生物来源追踪未发现任何人源细菌；相反，样品CU-110中的细菌被鉴定为有蹄类来源，并且CU-107中的细菌没有特定来源。在我们的河水样本中，阴离子和阳离子之间存在许多相关性（表S5[见脚注1]）。Na和Cl以及Na和HCO3、F、SO4、NO2、K、Ca、Br、Ti、as、Rb、Sr、Ba和U呈正相关（p<0.01）（p<0.05，均为阳性，图4）。这些元素之间也存在着积极而显著的相关性。此外，Mg与SiO2、V、Cr和Ni呈正相关（p<0.05）。NO2与电导率呈正相关。25个样本中的4个（CU-120、-121、-122和-132）都是在野外区域的西北部采集的，在地球化学上是不同的（图3、4和5）。这些样品具有最高或几乎最高的Cl、SO4、Br、NO2和Na浓度、场电导率和TDS（图4，红色符号）。这是仅有的五个样品中的四个含有低但可测量的As（1.0–1.4 ppb）。它们绘制在Piper图的一个不同区域（图5），并且与其他古巴河水样本相比，Rb、Sr、Ba和U的浓度（1.8–4.3 ppb）也更高。四个样品中有三个含有>115 mg/L的Ca和高浓度的Na、Cl

{"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":" ","pages":"4-10"},"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}

引用次数: 5

Decoupling Process from Form in Landscape Evolution Studies 景观演化研究中的形态解耦过程

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-02-01 DOI: 10.1130/gsatg422c.1

D. Hedding

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

根据Cruden(2003)的说法，“滑坡”一词最早是由J.D. Dana于1838年记录的。Varnes(1958)在其著名论文的标题中使用了“滑坡”，但随后在更新的迭代中放弃了该术语，转而使用“斜率”(见Varnes, 1978)。Varnes(1978，第11页)指出，这种变化的原因是“技术交流的改进需要深思熟虑和持续的努力来增加与单词含义相关的精度，因此术语滑动将不用于指代不包括滑动的动作。”后来，克鲁登(1991，第28页)提出，滑坡是“大量岩石、泥土或碎片沿着斜坡向下移动”，用于非正式的、非技术的用途。人们还提出了其他几个定义;然而，Shanmugam(2015)指出，“滑坡”一词缺乏概念清晰度。尽管如此，“滑坡”一词在文献中仍然根深蒂固，由于每个科学学科都使用自己的命名方案，它对不同的群体意味着不同的东西(Shanmugam, 2015)。在景观演化的研究中，在重力的影响下，大量物质下坡的转移对景观的形成起着重要的作用(Cendrero和Dramis, 1996)。因此，各种论文通常在量化侵蚀率(Roda-Boluda等人，2019)和/或构造和气候因素在风化中的作用(Emberson等人，2016)的背景下，评估斜坡过程和由此产生的质量运动在景观演变中的作用和意义。通常术语“滑坡”或“基岩滑坡”被用来描述物质下坡移动的过程(Egholm等人，2013;Roering et al.， 2001,2005)。然而，它们的使用表明对地貌学中过程和形式之间差异的认识不足，因为这些术语与作为离散地貌地貌的滑坡有着内在的联系，而与在景观演变中导致物质下坡运动的过程范围没有联系。此外，形态收敛(等性)表明，形态相似的地貌可以由不同的过程单独或联合形成，这使得正确识别地貌的过程起源变得复杂(Hedding, 2016;heding et al.， 2018)。尽管如此，术语“滑坡”通常被描述为负责物质下坡运动的过程，并且通过文献的重复和随后的接受而获得一定程度的信任(见Roering等人，2001)，而不是对实际过程-形式关系的认可。尽管措辞拙劣，“滑坡”一词有时被用作“大规模浪费”的同义词。然而，在景观演变过程中，物质下坡的运动可以通过一系列的物质消耗(运动)过程产生，从而形成地貌(例如，灾难性的泥石流和落石)，而不仅仅是物质沿着软弱面的运动，从而导致各种类型的滑坡。特别是，通过岩崩活动的物质的相对贡献可能是至关重要的，特别是在地震活跃地区，地震波沿着山脊线的地形放大，没有横向支撑，可以产生大量的碎片。因此，在地球科学所涵盖的学科(如地质学、地球化学、地貌学和沉积学)中使用的术语中，过程和形式的合并可能会导致对景观演化和剥蚀过程的理解有限，特别是在英语可能是研究人员的第二语言并且使用字面或直接解释的情况下。为了解决潜在的混淆，应该放弃“滑坡”一词，代之以地貌学中已确立的术语“大规模浪费”，以便在景观演化研究和其他地球科学中将过程与形式分离开来。质量损耗是一个包罗万象的术语，专门指造成物质下坡运动的过程。此外，在景观演化的词汇中，应该用“深层滑坡”来代替“基岩-滑坡”。为了避免进一步的混淆，有必要强调的是，“群体运动”是一个术语，用于描述通过群体消耗过程产生的最终地貌。

{"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":"30 1","pages":"6-6"},"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}

引用次数: 0

THOMPSON FIELD FORUM REPORT: Age and Carving of Grand Canyon: Toward a Resolution of 150 Years of Debate 汤普森菲尔德论坛报告:大峡谷的年代和雕刻:对150年争论的解决

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-02-01 DOI: 10.1130/gsat-tff-gc.1

K. Karlstrom, L. Crossey, E. Humphreys, D. Shuster, K. Whipple, R. Crow

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

自1869年J.W.鲍威尔探索科罗拉多河以来，美国西部大峡谷的年龄和演化一直备受争议。本文报道了2019年GSA汤普森实地论坛的结果，该论坛纪念鲍威尔首次访问150周年。在2019年GSA汤普森现场论坛上，“大峡谷的年龄和雕刻:解决150年的争论”有28名研究人员和年轻科学家参加(表1)，他们在最近的进展和正在进行的辩论的背景下讨论了大峡谷的年龄、地貌演化和切口历史的证据。目的是强调……的力量

引用次数: 0

The Future for Geoscience in the Context of Emerging Climate Disruption 新出现的气候破坏背景下地球科学的未来

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2020-02-01 DOI: 10.1130/gsat19prsadrs.1

D. Siegel

引用次数: 0

The Faint Young Sun Problem Revisited 再谈微弱的年轻太阳问题

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2019-12-01 DOI: 10.1130/GSATG403A.1

J. E. Spencer

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

由于太阳光度较低，地球和火星在其早期历史上本应是冰冻的世界，但事实并非如此，这挑战了我们对早期大气和表面条件的理解和/或对太阳演化的理解。这被称为“微弱的年轻太阳问题”。这个问题的一个解决方案是，在释放质量之前，太阳在年轻时的质量和亮度更大。然而，对恒星演化和行为的天体物理研究，包括最近对开普勒太空望远镜数据的分析，这表明质量损失既不充分，也发生得太早，不足以在大约4 Ga之后产生更明亮的太阳。或者，温室气体在温暖年轻的地球和火星方面出奇地有效。高浓度的二氧化碳和可能添加的生物CH4可能是促进太古代地球开放水域条件的主要因素。年轻的火星上有降水和流水的证据，包括数千公里长的河谷，问题更大。最近的研究表明，3-4 Ga河谷和火山口湖中的三角洲沉积物可能在<~107年内产生。在轨道参数有利的时期，高度瞬态的温暖期可能会导致在其他结冰条件下的短暂融化。大气中约1%-10%的H2和CH4更有可能出现季节性融化和径流，可能来源于火星地壳中橄榄石的蛇纹石化，并通过撞击和火山活动从冻土中释放，和/或直接来源于火山放气。最近公认的氢气和甲烷在以二氧化碳为主的厚大气层中吸收红外辐射的有效性，这一过程被称为“碰撞诱导吸收”，可能对解决火星微弱的年轻太阳问题至关重要。引言恒星能量产生所涉及的基本概念在20世纪50年代就已经为人所知，其中包括恒星光度随着时间的推移而逐渐增加的见解，因为热核聚变直接导致恒星核心密度的增加（例如，Burbidge等人，1957）（图1）。据计算，出生时的太阳光度约为现代光度的70%。地球应该有其可能冻结的年轻人的地质证据的想法逐渐被确定为与太古代地球表面液态水的越来越多的证据不一致。萨根和马伦（1972）首先解决了这个问题，他们提出大气中的氨对早期变暖至关重要。最近的机器人火星探测同样表明，火星早期地质历史上的温暖潮湿条件令人惊讶。太阳能产量低与早期地球和火星温暖之间的差异被称为“微弱的年轻太阳问题”（Ulrich，1975；Feulner，2012）。这篇文章是对太阳演化和地球和火星微弱年轻太阳问题的简要回顾，重点介绍了最近的发展。恒星能量产生恒星是由氢主导的星际气体云的引力收缩形成的。在收缩和绝热加热过程中，通过将氢核聚变为氦来增加恒星的能量生产，最终会终止引力收缩（例如，Haxton等人，2013）。数百万年来，氢聚变产生的氦积累在恒星核心，并增加核心密度，导致引力收缩和绝热加热，进而提高聚变率和能量产生。这一过程逐渐而连续地发生，导致核心温度和总光度增加（图1）（Bahcall等人，2001）。Jon Spencer，美国亚利桑那州图森市亚利桑那大学地球科学系，85721，spencer7@email.arizona.eduGSA Today，第29页，https://doi.org/10.1130/GSATG403A.1.版权所有2019，美国地质学会。CC-BY-NC。图1。太阳性质的演变（来自Bahcall等人，2001年）。还显示了日光亮度演化的简单近似（Gough的方程1，1981）。0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4

{"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":"29 1","pages":"4-10"},"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}

引用次数: 5

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 古代弧中的俯冲极性：呼吁将地质学和地球物理学结合起来，解读北美北科迪勒拉中生代构造史

Q1 Earth and Planetary Sciences

GSA Today

Pub Date : 2019-11-01 DOI: 10.1130/GSATG402A.1

T. Pavlis, J. Amato, J. Trop, K. Ridgway, S. Roeske, G. Gehrels

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

Terry L. Pavlis，德克萨斯大学地质科学系，美国德克萨斯州埃尔帕索79968;Jeffrey M. Amato，新墨西哥州立大学地质科学系，美国新墨西哥州拉斯克鲁塞斯88003;Jeffrey M. Trop，巴克内尔大学地质与环境地球科学系，美国宾夕法尼亚州刘易斯堡17837;Kenneth D. Ridgway，普渡大学地球、大气与行星科学系，印第安纳州西拉斐特47907;Sarah M. Roeske，美国加州大学戴维斯分校地球与行星科学系，美国加州95616;美国亚利桑那大学地球科学系George E. Gehrels，美国亚利桑那州图森85721

引用次数: 32