Maguse River thermokarst on till plain
Circular "hole" in Maguse River between Henninga and Maguse Lakes from altitude of ~100m. Several of these circular holes give the Maguse the appearance of classic "beaded drainage" (see images 0113 and 0115), but these thermokarst features are depressions in a till plain, probably created by melting ground ice. Because the till is bouldery and the flow of the river can be substantial, the upstream sides of these depressions often are distorted by delta-like deposits of boulders which build a ramp into the depression. Where well-formed, these delta ramps give the depressions an arrowhead appearance in plan view, with the "point" of the arrow downstream. These features are conspicuously developed along this reach of the Maguse River, but are so dense along the Geillini River, southeast of these photos, that they assume a distinctive en-echelon, or nested appearance. See images 0114, 0117 (Maguse River) and 0118 (Geillini River) to see the arrowhead morphology. Because they are so well developed on the Geillini River, I have informally referred to rivers ornamented with these distinctive "arrowhead features" as "Geillini Streams."
Updated 03/29/2010 AW