(1) The lower, elongate part of a valley glacier or outlet glacier. (2) A floating extension of a glacier or ice stream, laterally unconfined but markedly longer than wide.
Uncertain: unknown or not measured; Marked retreat: more than 20 m per year retreat; Slight retreat: 20m per year retreat; Stationary: Stationary; Slight advance: 20m per year advance; Marked advance:
more than 20m per year advancing; Possible surge: possible surge; Known surge: known surge; Oscillating: oscillating; Downwasting: stationary but rapidly losing mass through melting.