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Why are drumlins aligned with the direction of ice flow?

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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.

Drumlins are oval or elongated hills formed by the streamlined movement of glacial ice sheets across rock debris or till. Their alignment parallel to the direction of regional ice flow is a result of this streamlined process, which shapes the sediment into a characteristic form.12

The physical structure of a drumlin reflects the dynamics of the ice that created it: the stoss side (the side facing the glacier) is typically high and steep, while the lee side is smooth and tapers gently in the direction of ice movement. Furthermore, the internal composition of many drumlins exhibits a specific fabric, where the long axes of individual rocks and sand grains are aligned parallel to the flow of the ice. While the precise details of their formation are not fully understood, drumlins are believed to form subglacially near the margins of ice sheets, often occurring in large groups known as drumlin fields.12