as kames. Mounds along the frontal edge of the ice are called moraines. Wherever a subglacial tunnel began infilling, long winding formations known as eskers would form. The sweeping plain of sand and gravel beyond the ice margin and a terminal moraine is called an outwash plain . The materials left under the glacier when it melts back is called the ground moraine or till plain. Till is highly permeable and creates a large ground reserve for water. This formation is highly desirable for human economic development as a source of water. Stages of the Wisconsin episode Role in human migration Prehistoric human migration was likely greatly influenced by this last glacial period, as during much of the Wisconsin era, the formation of a land bridge known as Beringia across the Bering Strait is believed to have allowed human occupation of this area which provided potential access for some of the first humans to move between North America and Siberia in Asia (see Settlement of the Americas). Other human migration routes also opened during interglacial periods in both Europe and Asia. Flora and fauna North American flora and fauna species were distributed quite differently during the Wisconsin era, due to altered temperatures, surface water distribution, and in some cases coverage of earth surface by glaciers. A number of scientific studies have been conducted to determine species distribution, particularly during the Late Wisconsin and early to mid-Holocene. An example of findings is from the investigation of flora species using pollen core samples in present-day northern Arizona. Here in the Waterman Hills researchers found that Juniperus osteosperma and Pinus monophylla were early to mid-Holocene dominant trees, while Monardella arizonica has been a continuously present understory plant. Celtis reticulata is an example of a plant present in the early Holocene following Wisconsin glacial retreat, a species no longer present at the Waterman Mountains site. See also Pleistocene historic names References External links and references britannica.com reference Glaciology of Canada Glaciology of the United States Ice ages Pleistocene geology Pleistocene United States Quaternary Canada Quaternary Colorado Quaternary Michigan Quaternary Minnesota Quaternary Montana Quaternary Wisconsin Quaternary Wyoming Last Glacial Period