Active anhydrite hydration during weathering leading to crystallisation of secondary gypsum and significant volume expansion was investigated and documented by the authors at three sites: the environs of Walkenried (Germany), Dingwall (Canada), and Pisky (Ukraine). As a result of these processes, peculiar landscape forms were created: hydration domes and ridges with empty internal chambers, some of them large enough to be called hydration caves (German: Quellungshöhlen). Currently, there are only four recognised sites on Earth featuring such a unique landscape and with a large group of hydration caves in one place (the fourth site is in the Alebastrovyye Islands, Russia). These sites constitute a particularly valuable geological and geomorphological heritage, including potential geosites and geomorphosites which require special protection. Actively growing hydration domes and caves change shape and size within a short time span, on the scale of months, years, or decades. Their study and proper protection require these changes to be monitored. Several different methods of documentation were applied in the field in order to document continuing morphological changes. The practical aspects of the use of each of these methods were assessed, demonstrating that the photogrammetric methods offer the greatest utility; not only are they the most efficient (fast and sufficiently precise) but also, compared with other methods, they yielded the most complete results. The key documentation of outcrops in Canada and Ukraine was executed with the application of terrestrial photogrammetry at Pisky (GoPro camera) and aerial photogrammetry at Dingwall (unmanned aerial vehicle). Application of these methods enabled the recording of the morphology associated with the hydration process in the form of 2.5D and 3D models as well as of orthophotomaps. The maps and the models were created using the Photoscan programme. The authors demonstrate that the photogrammetric models can be used for spatial morphological analysis of hydration forms in the ArcGIS programme. Repetition of this documentation in future will enable analysis of the morphological changes expected to occur during the progressive expansive hydration of anhydrite.

中文翻译：

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独特的水合洞穴及其推荐的摄影测量方法

作者在以下三个地点研究和记录了风化过程中主动石膏水合，导致次生石膏结晶和大量体积膨胀，这些地点分别在Walkenried（德国），Dingwall（加拿大）和Pisky（乌克兰）的三个地点进行。这些过程的结果是，形成了奇特的景观形式：水合圆顶和山脊，其内部腔室为空，其中一些大得足以被称为水合洞穴（德语：Quellungshöhlen））。目前，地球上只有四个公认的地点，具有如此独特的景观，并且在一个地方有大量的水化洞穴（第四个地点在俄罗斯的Alebastrovyye群岛）。这些遗址构成了特别有价值的地质和地貌遗产，包括需要特殊保护的潜在地理位置和地貌。活跃的水化圆顶和洞穴在短短的几个月，几年或几十年的时间内改变了形状和大小。他们的学习和适当的保护要求对这些更改进行监视。为了记录连续的形态变化，在现场应用了几种不同的记录方法。评估了每种方法使用的实际情况，表明摄影测量方法提供了最大的实用性。它们不仅效率最高（快速且足够精确），而且与其他方法相比，它们还可以提供最完整的结果。在加拿大和乌克兰，露头的主要文件是通过在Pisky（GoPro摄像机）进行地面摄影测量和在Dingwall（无人飞行器）进行航空摄影测量来执行的。这些方法的应用使得能够以2.5D和3D模型以及正射影像图的形式记录与水化过程相关的形态。地图和模型是使用Photoscan程序创建的。作者证明，摄影测量模型可用于ArcGIS程序中水化形式的空间形态分析。