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Plural: creithiau rhewlifol a lenwyd â chlogfeini a choblau
Definition: Cynefin morol lle ceir rhych a adewir mewn is-haen galed o graig gan weithrediad rhewlif, sy’n llawn cerrig mawr. Yn aml, maent yn hafan i gregyn gleision a rhywogaethau morol eraill.