One of the scoriaceous retaining walls on either side of a lava channel. Four types are recognized: initial levées form when the yield strength of the lava permits the margins of a flow to remain stationary and crystallize while the central part of the flow continues to move; accretionary levées are formed near boccas where piles of surface clinker are accreted to the flow margins; rubble levées form when the sides of a flow expand outwards by the avalanching of surface and marginal crystalline clinker; and overflow levées form when lava repeatedly overflows existing rubble levées.