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How do glacial landforms provide evidence of past ice ages?

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esker: Nunavut — glacial landform Eskers, or narrow ridges of gravel and sand left by a retreating glacier, wind through western Nunavut, Canada, near the Thelon River.

Glacial landforms serve as vital geological evidence of past ice ages by recording the erosional and depositional activity of ice sheets that once covered vast regions of the Earth. These features remain visible today in areas now devoid of glaciers, provided they have not been obscured by subsequent landscape processes.12

Erosional Evidence

Glaciers reshape the landscape through intense abrasion and plucking. Key indicators include:
* U-shaped Valleys: Glaciers transform narrow, V-shaped river valleys into broad, parabolic U-shaped valleys with steep sidewalls.32
* Alpine Features: The formation of cirques (amphitheatre-shaped hollows), arêtes (knife-edge ridges), and horns (sharp peaks) provides clear evidence of past alpine glaciation.32
* Striations and Gouges: Scratches and crescentic marks on bedrock, such as chatter marks, indicate the direction of former ice movement.4

Depositional Evidence

Glaciers leave behind distinct sediment deposits:
* Moraines: Ridges of till mark the former margins of ice sheets.52
* Drumlins and Eskers: Drumlins are streamlined hills aligned with ice flow, while eskers are sinuous ridges formed by subglacial meltwater.52
* Erratics: These glacier-transported rocks differ from local bedrock and were instrumental in the initial scientific recognition of past ice ages.6