How do lateral moraines form along the sides of a valley glacier?

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glacier Perito Moreno Glacier, Los Glaciares National Park, Argentina.

Lateral moraines form along the sides of a valley glacier through the accumulation of rock debris derived from the adjacent valley walls. This material reaches the edge of the glacier primarily through processes of erosion and avalanche.1

As the glacier moves, it acts as a conveyor, transporting this debris along its margins. When the glacier eventually recedes, this accumulated material is deposited as an elongate ridge along the valley slopes, marking the former side margins of the ice. These features are distinct from other types of moraines, such as terminal moraines or medial moraines, due to their specific location and the process of their formation along the valley sides.231