Before revision: The Geomorphic Environments group has the following subgroups: (1) Coastal Marine and Estuarine, (2) Lacustrine, (3) Fluvial, (4) Solution, (5) Eolian, (6) Glacial, (7) Periglacial, (8) Mass Movement, (9) Volcanic and Hydrothermal, and (10) Tectonic and Structural .
After revision: In this classification, ridges are in the following subgroups: (1) Coastal Marine and Estuarine, Lacustrine, Glacial, Volcanic and Hydrothermal, Tectonic and Structural .