dyynityyppejä

Dyynityyppejä refers to the classification of dunes based on their shape and formation. These landforms are created by the movement of windblown sand. The most basic classification distinguishes between active dunes, which are currently shifting, and relict dunes, which are no longer subject to significant wind erosion and may be stabilized by vegetation.

Several common dune types exist. Barchan dunes are crescent-shaped with the horns pointing downwind. They form in areas with a constant wind direction and limited sand supply. Transverse dunes are also crescent-shaped but are oriented perpendicular to the prevailing wind, often forming extensive fields. Linear dunes, also known as seif dunes, are long, parallel ridges that can extend for many kilometers. Their formation is complex and is thought to involve bidirectional wind patterns. Star dunes are large, isolated dunes with multiple arms radiating from a central peak. They form in areas with variable wind directions and are often found in hyperarid environments.

Parabolic dunes are U-shaped with the arms pointing upwind. They typically form when vegetation anchors the dune crests, while the wind erodes the central trough. Climbing dunes form on the windward slopes of larger obstacles, such as mountains, where the sand is deposited as it moves upslope. Falling dunes are similar but form on the leeward side of obstacles, where sand tumbles down the steep face. The specific type of dune that forms is influenced by factors such as sand availability, wind speed and direction, and the presence of vegetation or topography.