Visualizing Strain in Rocks with Interactive Computer Programs

地质学(42)应变是构造地质学中的一个基本主题，研究人员致力于量化岩石中的应变以了解变形组构的发展，并检查褶皱和断裂带的应变梯度以限制其形成机制。这个CCLI类型I项目为构造地质学专业的学生提供了从岩石中收集和分析数据并将变形与大型结构联系起来的机会。正在开发的两个计算机程序和附带的教程为学生提供了确定岩石应变的机会，并为他们提供了获得数据采集和误差分析经验的机会。学生们还将学习使所有量化应变的尝试复杂化的重要问题，例如标记对象和基质之间的延展性对比、标记对象的初始形状和分布以及变形过程中的面积或体积变化。因此，这些练习的价值远远不止是训练学生测量岩石中的应变；这些项目也为学生提供了一个机会，以批判性地检验任何试图量化自然过程的假设和限制。估算岩石应变的两种常用方法是Rf/Phi法和中心对中心法。两者都需要进行多次测量，将结果绘制在图表上，并解释图表中的模式以估计应变。学生们通常很难将变形岩石中测量的物体与图表联系起来。正在创建的程序是连续和瞬时地将岩石的图像连接起来，因为变形是通过线性变换来模拟的，图形用于计算应变。这种方法为学生提供了变形和原本抽象的图形显示之间的视觉联系。一个原型程序正在改进中，并正在创建教程，以帮助学生熟悉确定应变的RF/Phi方法。第二个类似的用中心到中心的方法测量应变的程序和教程也在开发中。第三个教程是关于应变分析的高级处理，描述了如何使用这两种方法来测量某些岩石中的应变，以将应变划分为形状变化和面积变化分量。这些程序是用Java编写的，因此它们可以在几乎任何一台计算机上运行。这些教程以带有程序屏幕截图的文本文档的形式提供，也可以以PowerPoint演示文稿的形式在课堂上使用。更广泛的影响。正在开发的程序和相关教程将影响构造地质学的教学，构造地质学是几乎所有地质学专业的核心课程。这些课程和教程通过加深对常用应变方法工作原理的理解，改善了构造地质学的本科课程。这些程序也被用来为地质学入门课程演示一些应变的基本原理。为了支持广泛传播和增加在其构造地质学课程中使用这些程序的地质学教员的数量，正在国家和地区地质学会议上举办讲习班。所有材料均可免费获取，并可从威廉姆斯学院地球科学和信息技术网页下载。

Geology (42)Strain is a fundamental topic in structural geology, and researchers endeavor to quantify strain in rocks to understand the development of deformation fabrics, and examine strain gradients in folds and fault zones in order to constrain mechanisms of their formation. This CCLI Type I project is providing students in structural geology opportunities to gain confidence gathering and analyzing data from rocks and relating deformation to large-scale structures. The two computer programs and accompanying tutorials being created are providing students with opportunities to determine strain in rocks and an opportunity for them to gain experience in data acquisition and error analysis. Students are also learning about important problems that complicate all attempts to quantify strain, such as ductility contrast between marker object and matrix, initial shape and distribution of marker objects, and area or volume change during deformation. Thus, the value of such exercises goes far beyond training students to measure strain in rocks; these projects also are providing an opportunity for students to critically examine the assumptions and limitations of any attempt to quantify a natural process.Intellectual Merit. Two common methods for estimating strain in rocks are the Rf/Phi and center-to-center methods. Both require making numerous measurements, plotting the results on graphs, and interpreting patterns in the graphs to estimate strain. Students commonly have trouble connecting the objects measured in deformed rocks with the graphs. The programs being created are continuously and instantaneously linking images of the rocks, as deformation is simulated by linear transformations, with the graphs that are used to calculate strain. This approach is giving students a visual link between deformation and the otherwise abstract graphical display. A prototype program is being refined and tutorials are being created to help students become familiar with the Rf/Phi method for determining strain. A second similar program for measuring strain by the center-to-center method and tutorials are also being developed. A third tutorial is for advanced treatments of strain analysis describing how both methods can be used to measure strain in some rocks to partition strain into shape change and area change components. The programs are being written in Java, so they can run on virtually any computer. The tutorials are available as text documents with screen captures of the programs, and as PowerPoint presentations for use in the classroom. Broader Impact. The programs and associated tutorials being developed will impact the teaching of structural geology, a core course taken by nearly all geology majors. The programs and tutorials are improving undergraduate courses in structural geology by fostering a deeper understanding of how commonly used strain methods work. The programs are also being used to demonstrate some basic principles of strain for introductory geology courses. To support wide dissemination and increase the number of geology faculty that are using the programs in their structural geology courses, workshops are being held at national and regional geology meetings. All material is freely available and is downloaded from the Williams College Geosciences and Information Technology web pages.