Why can outlet glaciers resemble the lower sections of valley glaciers?

Outlet glaciers resemble the lower sections of valley glaciers because both are constrained by the surrounding topography as they flow through channels. While continental ice sheets typically bury the underlying landscape, their margins can become controlled by local relief where the ice is thinner. In these areas, the ice forms tonguelike protrusions known as outlet glaciers.12

When viewed in isolation, these outlet glaciers are nearly indistinguishable from the lower reaches of a large valley glacier system because both types of ice masses are channeled by the terrain and exhibit similar flow characteristics. Consequently, they often produce virtually identical landforms, though the scale of these features may differ depending on the size of the glacier system.2