Glaciated Landforms (NLWv3)

This layer shows the extent of Wisconsin and Würm glaciation in blue, overlapping the preceding glacial landforms shown in purple. The ages of these periods of glaciation are as follows: The Wisconsin glacial stage began approximately 75,000 to 100,000 years ago and ended around 11,000 years ago. The Würm glaciation age lasted slightly longer, spanning approximately 115,000 to 11,700 years ago. The Pre-Wisconsin Würm glaciation occurred up to 2.6 million years ago and ended prior to the Wisconsin and Würm glaciations. The glaciated landform features were identified either as being sufficiently north of the line of moraines, or by using high resolution hill-shaded relief models that showed terminal moraine features immediately south of features that had been scoured by the movement of the glaciers. This layer is part of the Named Landforms of the World version 3 (NLWv3) collection. All layers in the collection are available in the ArcGIS Online Group named Named Landforms Of the World v3 (NLWv3) Layers and Maps.本图层以蓝色标注威斯康星冰期（Wisconsin glaciation）与玉木冰期（Würm glaciation）的分布范围，与紫色所示的前期冰川地貌相互叠加。上述冰期的年代信息如下：威斯康星冰期始于约7.5万至10万年前，终止于距今约1.1万年前；玉木冰期持续时长略久，跨度约为11.5万至1.17万年前。前威斯康星-玉木冰期可追溯至260万年前，并于威斯康星冰期与玉木冰期之前结束。冰川地貌特征的识别遵循两类标准：一是位于冰碛线以北足够远的区域；二是借助高分辨率山体阴影地形模型，识别出紧邻冰川侵蚀区域南侧的终端冰碛特征。本图层隶属于《世界命名地貌第三版》（Named Landforms of the World version 3，简称NLWv3）数据集集合。该集合内的所有图层均可在名为「世界命名地貌第三版（NLWv3）图层与地图」的ArcGIS Online群组中获取。