Raet

Raet is the largest terminal moraine in Scandinavia. It was formed during the end of the last glacial period, 12,800–11,500 years ago, in one of the latest advances of the glaciers. The moraine system extends from Finland, where it is known as Salpausselkä, through Sweden into Østfold in southeast Norway, across the Oslofjord and around the tip of southern Norway, where Raet National Park is located in Agder, then north to northern Norway and the Kola Peninsula in northwest Russia. In several regions there is more than one moraine, an older on the coast or underwater and a younger further inland. The moraines have created numerous lakes by damming watercourses, and several stretches have been used as roads since ancient times. In Norway, both Raet National Park and Jomfruland National Park are along the moraine. The moraines were left by the retreat of the Fenno-Scandian ice sheet at the end of the Weichselian glaciation, 12,800–11,500 years ago. As the ice retreated, its furthest extent was marked by a deposit of rocks in a variety of sizes, which formed a ridge. Weathering causes the smaller material to sink, leaving large rocks on the surface. The retreating ice sheet left productive agricultural land in many places; the moraine dammed watercourses, creating lakes. In Norway, the term ra, from rǫð, an Old West Norse word for a gravel ridge, is the name of several farms located along the course of the moraine, notably Ra in Horten municipality, and has come to be the general term for a terminal moraine. The relative ages of the moraines in Østlandet have been studied. In south Finland, the two parallel moraines are known as Salpausselkä. In Sweden, they form the Central Swedish ice-edge zone; the moraine is particularly noticeable at Hindens Rev, where it forms a peninsula jutting out into the western part of Lake Vänern. The moraine crosses into Østfold in southeast Norway at Halden, crosses under the Oslofjord from Moss to Horten, then runs across Vestfold, where Riksvei 19 and the old E18 follow its course.