Beaded drainages are features of thermokarst (pitted, hummocky landscapes formed by melting permafrost). Necklace-like arrangements of button-shaped pools joined by short channels, these drainages form on ground underlain by vertical ice wedges. Such ice wedges develop in Arctic regions when the ground contracts and splits, allowing water to enter the rifts and freeze. Over these, streams carve narrow, deep channels through turf and peat to the sediment underneath. At intersections of melting ice wedges, pools form. When encountering smaller pools, a traveler or animal might wade or hop across. Larger ponds can be ten feet deep and eighty feet wide. Beaded drainages decorate silt lowlands of the western Canadian Arctic and northern Alaska, often in the company of pingos and thaw lakes.