Drumlin Drumlin A drumlin, from the Irish word "droimnín" ("littlest ridge"), first recorded in 1833, and in the classical sense is an elongated hill in the shape of an inverted spoon or half-buried egg formed by glacial ice acting on underlying unconsolidated till or ground moraine. Drumlins occur in various shapes and sizes, including symmetrical (about the long axis), spindle, parabolic forms, together with transverse asymmetrical forms; their long axis is parallel to the direction of movement of the formative flow at the time of formation. Drumlins are typically long, less than high and between wide. Drumlins generally have a length:width
Glacial survival hypothesis Glacial survival hypothesis According to the northern cryptic glacial refugial hypothesis (or glacial survival hypothesis), during the last ice age cold tolerant plant and animal species (e.g. Norway spruce and Norwegian lemmings) persisted in ice-free microrefugia north of the Alps in Europe. The alternative hypothesis of no persistence and postglacial immigration of plants and animals from southern refugia in Europe (southern refugia paradigm) is sometimes also called the tabula rasa hypothesis. Over the past plants and animals have persisted through long periods of climate change including several glacial and interglacial periods. There is a long-standing debate on what happened to