En analys av De Geer-moräners bildningsmiljö med hjälp av LiDAR-bilder

Sammanfattning: Gerard De Geer was the first one to identify De Geer-moraines, and has since then been mapped by many other studies around the world.  The focus of this study was to examine the environment the ridges form in, regarding the water depth during creation, the importance of topography and the melting rate of the ice. Using airborne Light Detection and Ranging  (LiDAR) data, De Geer- moraines were mapped around eastern Norrbotten county, including Piteå, Boden and Luleå. A total of 14 651 De Geer-moraines were identified over the selected area. Six parameters were analysed during this study; length, orientation, steepness, distance between ridges, current ground level and depth below highest shoreline. In some areas, ridges showed a high, local steepness, while other study sites showed ridges with a varied interconnected form, from straight, to convex and concave. Prominent De Geer-moraines had been identified, where the mean distance between the ridges was calculated to 345 m. Furthermore, other glacial formations (drumlins, flutings, rogen moraines and eskers) showed a relationship to De Geer-moraines, either with a similar angle or a perpendicular relation. A great water depth showed a significant role in the creation of the ridges, with 75% of the identified De Geer-moraines formed in a water depth greater than 150 m. De Geer- moraines found on topographic lows tend to have an interconnected concave form, while over or close to elevated areas; they’re slightly convex. The mean distance between prominent ridges showed a connection to the average retreat rate of the last ice, which suggests that prominent ridges had been formed annually.