Mackenzie Delta

The maximum extent of the Laurentide Ice Sheet in the Mackenzie Delta area was 30,000 years ago. The vast delta, with its branching channels, ponds and wetlands, covers more than 13,000 km2 of alluvial coastal plain. The delta stretches nearly 210 kilometers from north to south and is 50 to 80 kilometers wide. Below Fort McPherson, the Mackenzie River divides into several major channels and hundreds of smaller tributaries, the largest of which flows north-northeast and empties into the Beaufort Sea west of Tuktoyaktuk. The Mackenzie Delta is a labyrinth of shifting channels and pseudokarst lakes. Most of the land in the delta is permafros. Bedrock is at great depth, and patches or taliks of unfrozen ground are controlled by shifting channels. Retrogressive thaw slumps, up to 200 meters wide, are common where ground ice is exposed by bank erosion. Rivers and lakes are ice-covered for more than half the year. The Mackenzie River carries a large load of sediment, transporting about 128 million tonnes to its delta each year. A characteristic feature of the delta are the numerous pingos (1400, the largest population in the world). They are conical, ice-cored, 50 meters high, and >100 meters in diameter at the base.