 Since the glacier was first observed to be forming and actively flowing in the late 1980s , most scientists working on the mountain have referred to it informally as the " crater glacier " . That name has been in wide use with the public ( at least those who were aware of the glacier 's existence ) for the two decades since the glacier formed , and has appeared in several scientific publications too . A single scientific paper , the most complete published study of the glacier to date , referred to it as the " Amphitheater glacier , " but that name has not been used otherwise . 
