TWO GLACIAL SIGNATURES: IN OR OUT

Glaciated landscapes possess a distinctive geomorphic signature. Thus it is not surprising that examination of landform associations over several spatial scales reveals common patterns. Ice geometry either abuts topographic obstructions forming an embayment in the ice margin (In) or follows lowland depressions extending along the depression (Out) and each has a slightly different signature derived from a common forcing.

Is: Obstacles typically mark ice margin positions. Interior of the margin are channel complexes, which give way to streamlined topography. Most of the constructional drift exterior to the margin is planer outwash and associated channels.

Out: The lowlands display a systematic pattern. The outer rim is often diffuse, typically lacks well-developed landforms and may be difficult to distinguish in all but the flattest terrain. Next in are distinct moraine loops and a significant increase in meltwater channels. Lineated topography lie interior to ice-margin positions. Further up flow line are depressions containing lakes.

It is contended that these landscape patterns result from the same climate cycle driving the glacial advance retreat pattern – the cold pushes the glacier out with little erosion, oscillating climate conditions produces moraine belts, and warming generates abundant meltwater prior to the final collapse of the glacier system. Ice-flow speed differences impart varied lineation types.