dryas

Dryas is a small genus of flowering plants in the rose family (Rosaceae), commonly known as mountain avens. The genus comprises a few species native to Arctic and alpine regions of the Northern Hemisphere, most notably Dryas octopetala and Dryas drummondii. Dryas plants are low-growing, evergreen perennials that form cushion-like mats in rocky habitats. They have rounded, lobed leaves and white flowers that bloom in spring and summer, contributing to alpine and arctic flora as ground cover and early-season nectar sources.

The term Dryas also appears in geoscience as the Younger Dryas, a climatic re-advance that briefly interrupted the gradual warming at the end of the last Ice Age. The Younger Dryas lasted roughly from 12,900 to 11,700 years ago and is characterized by a sudden return to cool conditions in the Northern Hemisphere, followed by a return to warmer Holocene conditions. It is named after Dryas pollen found in European sediment records, which indicates a prominent Dryas-type vegetation during that interval and serves as a stratigraphic marker. Various hypotheses have been proposed for its cause, including changes in Atlantic Ocean circulation, freshwater input from melting ice sheets, and disruptions to global climate systems. The end of the Younger Dryas coincided with the onset of the current warm Holocene epoch.