Collaborative Research: Transient landscapes, temporally variable erosion rates, and the impact of glaciation and climate change on landscape morphodynamics

合作研究：瞬变的景观，随时间变化的侵蚀速率，以及冰川和气候变化对景观地貌动态的影响。弗吉尼亚理工大学詹姆斯·斯波蒂拉刘易斯·欧文，辛辛那提大学在过去的二十年里，地质学家已经确定，侵蚀和气候，作用于地球表面的过程，直接影响板块构造和造山，与地球动力学有关的过程？S(地壳和上地幔)。对侵蚀有效性有巨大影响的一个气候变化是温度，表现为河流侵蚀(即河流侵蚀)和冰川侵蚀之间的巨大差异。无数研究将数百万年前全球侵蚀的深刻加速归因于全球变冷和冰川扩张。这导致了这样一种想法，即冰川是绝对有效的侵蚀媒介，就像嗡嗡声的锯子一样，可以像板块构造推高山脉一样迅速地侵蚀岩石。然而，当仔细研究这一点时，有大量观察表明，这种行为更复杂。我们在构造活跃地区发现了严重冰川山脉，这些山脉可能正在非常缓慢地被侵蚀。也有冰川山脉可能经历了快速侵蚀，尽管以冰层为主(通常与缓慢侵蚀有关)和缺乏构造抬升。这些观察表明，可能存在复杂的条件，作为极快速、有效的冰川侵蚀开始的阈值。为了检验这一点，我们将量化哪些因素作为控制山脉侵蚀对冰川反应的阈值，包括岩石抬升速度、降水和构造起伏等因素。这将通过扩展冰川侵蚀控制的案例知识，通过量化四个非常不同的山区的侵蚀速度年表和侵蚀深度来实现，这四个非常不同的山区跨越一系列条件，包括阿拉斯加的Chugach和Kenai山脉、苏格兰西北部的Chugach山脉和新英格兰的总统山脉。在每个地点，我们将测试侵蚀是否随着冰川发展的特定阶段的开始而加速，方法是使用几种方法测量侵蚀速率，这些方法包括放射性氦热年代学(百万年时间尺度)和宇宙成因测年、光激发发光和沉积记录(跨越一万到一百年)。通过促进我们对侵蚀、气候和构造的理解，我们实际上将有助于满足人类与生俱来的好奇心，即我们周围的风景是如何形成的。我们还将使我们能够更好地、更具预测性地了解冰川和高山地貌如何应对气候变化，这具有及时和实际的重要性。在我们研究的同时，我们的教育和博物馆推广计划将有助于联系学生和普通公众，激发人们对地球过程的好奇心，同时传达如何通过实验来框定和检验地球科学问题的经验。

Collaborative Research: Transient landscapes, temporally variable erosion rates, and the impact of glaciation and climate change on landscape morphodynamics.James Spotila, Virginia TechLewis Owen, University of CincinnatiOver the past two decades, geologists have determined that erosion and climate, processes that work at the Earth?s surface, directly influence plate tectonics and mountain building, processes linked to the dynamics of Earth?s interior (crust and upper mantle). One climatic variation that has enormous influence of the effectiveness of erosion is temperature, as represented by the vast difference between erosion by rivers (i.e. fluvial erosion) and glaciers. A profound global acceleration in erosion several million years ago has been ascribed in countless studies to the onset of global cooling and the expansion of glaciers. This has lead to the idea that glaciers are absolutely efficient agents of erosion, acting like buzz saws that can erode rock as fast as plate tectonics pushes up mountains. Yet when this is examined in detail, there are numerous observations that suggest the behavior is more complex. We have identified heavily glaciated mountain ranges in tectonically active areas that may be eroding very slowly. There are also glaciated mountain ranges that may have experienced rapid erosion, despite being dominated by frozen beds (normally linked to slow erosion) and a lack of tectonic uplift. These observations suggest that there may be complex conditions that operate as thresholds for the onset of the extremely rapid, efficient glacial erosion. To test this, we will quantify what factors act as thresholds that control the response of mountain erosion to glaciation, including the factors of rock uplift rate, precipitation, and tectonic relief. This will be accomplished by expanding the case knowledge of glacial erosion controls, by quantifying chronologies of erosion rate over a range of timescales and erosive depths in four very different mountainous regions that span a range of conditions, including the Chugach and Kenai Ranges in Alaska, northwest Scotland, and the Presidential Range of New England. In each location we will test whether erosion accelerated with the onset of a specific stage of glacial development, by measuring erosion rates using several methods of radiogenic helium thermochronology (million year timescale) and cosmogenic dating, optically stimulated luminescence, and sedimentary records (spanning ten thousand to a hundred years). By contributing to our understanding of erosion, climate, and tectonics, we will in effect help satisfy an innate human curiosity for how the landscape around us formed. We will also enable a better, more predictive understanding for how glacial and alpine landscapes respond to climate change, which is of timely, practical importance. In parallel with our research, our educational and museum outreach program will serve to connect to both students and the general public, kindling curiosity for Earth processes while conveying an experience of how geoscience problems are framed and tested through experimentation.