The Structural Glaciology of a Temperate Valley Glacier: Haut Glacier d’Arolla, Valais, Switzerland

Abstract

This paper describes the structural glaciology of Haut Glacier d’Arolla, a small valley glacier fed by two distinct accumulation basins in the Swiss Alps. A considerable body of field data is presented alongside observations from ground and aerial photographs. Suites of structures identified in the field and from aerial photographs are first described in nongenetic terms before being assigned regular structural terms. Haut Glacier d’Arolla is dominated by primary stratification, which is progressively folded and eventually transposed into longitudinal foliation as it moves into the glacier tongue. Crevasses and crevasse traces cross-cut and in places displace primary stratification and longitudinal foliation. Crevasse traces are formed by the closure of crevasses or may represent tensional veins. On their journey downglacier, crevasse traces become increasingly rotated. Close to the snout, some crevasse traces become reactivated as thrust faults. Strain ellipses, derived from the velocity field, show progressive deformation downglacier (cumulative strain). The shapes of the strain ellipses agree with inferences made concerning the orientation and magnitude of strain from observations of structures in the field. Independent modeling of cumulative strain shows good agreement with the development of longitudinal foliation in a simple shear regime. However, there are inconsistencies in the relationship between modeled cumulative strain and other structures.