Engineering Geological Map of Lower Saxony 1: 50000 – Saltstock elevations (WMS service)

Subrosion is the underground leaching and transport of mostly easily soluble rocks. Subrodable are chemical sediments, such as the easily soluble chlorides rock salt and potassium salt, sulphate rocks such as gypsum and anhydrite (sulfate carbonate) and also the heavy soluble carbonate rocks e.g. limestone (carbonate carbonate). Most damage in Lower Saxony is due to the leaching of sulphate rocks. In the case of subrosion, a distinction must be made between regular and irregular leaching. A regular leaching takes place on the surface of the subrodable rock and leads to wide-ranging, usually low drops of the terrain. Irregular leaching focuses on a small-scale, narrowly-limited area and can lead to the formation of caves, cloaks or coagulation. It progresses in solid rocks, especially along clefts or joints in the rock. Therefore, loosened mountain areas in tectonic fault zones are also usually areas of intense subrosion. If the boundary load capacity of the mountain above a cavity is exceeded, this cavity can collapse and break through to the earth’s surface (earthfall). The layer strength of the soluble rock and thus the possible size of a cavity are decisive for the size of the burglary on the terrain surface. About 50 percent of the earthfalls in Lower Saxony have a diameter of up to two meters and at about 40 percent the diameter is between two and five meters. Although these diameters seem quite small, the effects on buildings can be very large. In the map ISH50, on the basis of the Geotectonic Atlas of Northwest Germany, 1:100.000 Saltstock highlands were identified, in which salt rocks above -200 m NN – in a few exceptions above -300 m NN – occur and are surrounded by groundwater-containing layers. Here soil falls can be caused by leaching in the area of the salt level and by leaching in the area of the plaster hat. The information shown in the map does not replace ground investigation in accordance with DIN EN 1997-2 (DIN 4020).潜蚀作用（Subrosion）指对以易溶岩石为主的对象开展的地下溶蚀与搬运过程。可发生潜蚀的岩石包括化学沉积岩：如易溶的氯化物类岩盐与钾盐、硫酸盐类岩石（如石膏与硬石膏，即硫酸盐碳酸盐岩），以及高可溶性碳酸盐岩，例如石灰岩（碳酸盐碳酸盐岩）。下萨克森州的多数地质灾害均由硫酸盐类岩石的溶蚀作用引发。 针对潜蚀作用，需区分常规溶蚀与非常规溶蚀两类。常规溶蚀发生在可潜蚀岩石的表面，会引发大范围且通常幅度较小的地形沉降。非常规溶蚀则集中于小范围、受局限的区域，可形成溶洞、覆层或凝结体，并在硬质岩石中发育，尤其沿岩石的裂隙或节理扩展。因此，构造断层带内的松散山体区域通常也是潜蚀作用强烈发育的区域。 当溶洞上方山体的边界承载能力超出阈值时，溶洞便会发生坍塌并贯通至地表（即地表塌陷，earthfall）。可溶性岩层的层间强度以及由此决定的溶洞最大规模，是决定地表塌陷幅度的关键因素。下萨克森州约50%的地表塌陷直径不超过2米，约40%的塌陷直径介于2至5米之间。尽管此类塌陷的直径看似不大，但对建筑物的破坏可能极为严重。 在基于《德国西北地质构造图集》编制的ISH50地图中，已识别出1:10万比例尺的盐丘高地（Saltstock highlands）分布区：该区内赋存海拔高于-200米德国法定海平面（NN）的盐岩，少数区域的盐岩海拔高于-300米德国法定海平面（NN），且盐岩周边分布有含含水层。此处的土壤塌陷可由盐岩层面的溶蚀作用以及石膏盖层区域的溶蚀作用引发。 本地图所展示的信息，不得替代符合DIN EN 1997-2（原DIN 4020）标准的地面勘察工作。