Historical geography — clay extraction

Historical file with locations where clay extraction has taken place in history. The areas suitable for clay extraction were plotted (about 60 centimetres on average) and their ground level was greatly reduced, making them well recognisable in the landscape, between the unexcavated higher plots. Several hundred hectares of clay land must have been excavated over the centuries. Clay extraction along the (former) sea dikes is linked to various phases of dike construction and reinforcement, for which the required clay was inserted as much as possible in the immediate vicinity. A number of these ‘dyks-delten’ or dike pits are now under management as a nature reserve.本历史档案收录了历史上开展过黏土开采作业的点位信息。适宜黏土开采的区域均经测绘标定（平均开采深度约60厘米），开采作业使得区域地表高程大幅降低，因此这些采坑在未被开采的周边高地景观中极易辨识。数个世纪以来，累计被开采的黏土土地面积可达数百公顷。沿（原）海堤开展的黏土开采活动与海堤建设及加固的多个阶段紧密关联，此类工程所需的黏土均尽可能就近就地取用。其中不少“dyks-delten”（海堤采坑）如今已作为自然保护区进行管护。