South Cascade Glacier is one of the four "benchmark glaciers" that is monitored by the USGS and its mass balance has been monitored since 1959.[3] Its area has declined from 2.71 km2 in 1958 to 1.8 km2 in 2015 representing an area loss of 34%.[3][4] Between 1958 and 2009 South Cascade Glacier lost nearly a half of its volume.[5]