A glacier on the north side of the volcano also extended along the west side until recent years. The lack of references on the glacier in historical sources, however, makes it very difficult to document its evolution in (Table 0). Mention is made of the glacier accounts conquest, dimensions. dating from the period of the Spanish but no data are provided regarding its Frequent remarks are found in the old documents about the difficulties involved in crossing the levels of permanent snow before ascending to the crater from the south side of the glacier (e.g. Cort&, 0000 or Diaz de0 Castillo, 0000).