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Abstract: The Red Lake is one of the few great natural lakes formed by a landslide in Romania with a surface of 30 ha. Today, specialists have two theories about the triggering mechanism. The first one accepts that the landslide was triggered in 1837 during a heavy rainfall period. The second one refers to the earthquake from January 11 (January 23 in new calendar) 1838, which had a magnitude on Gutenberg – Richter scale of 6.7 or even 7.5. During the field work we found another active landslide, situated on the old landslide, but smaller than the older one (3 ha). The materials involved are ranging from silt to boulders and the relief is chaotic. The mapping is difficult to achieve because of the thick forest, generally composed by coniferous like Picea abies and Abies alba. The motion of the new landslide was of a few meters and relatively smooth. This fact is proven by the tilted trees, which have a large parabolic trunk without visible scars. By means of dendrogeomorphology we tried dating the new landslide. The method involves extraction of increment cores from the tilted trees located on the landslide, but also of cores from undisturbed trees located near the site, necessary to build the reference chronology. For extracting the cores, an increment borer with 40 cm length and 6 mm diameter provided by Suunto was used. The increment borer was introduced into the trunk and an extractor provides a core of 5 mm in diameter. The landslide samples for dating were collected out of 20 tilted trees, 15 of them located in the front or lateral lobe of landslide. The results relieve that at least two major movements of the new landslide occurred in 1953 and 1979.

Keyword: Red Lake, landslide, natural dam, dendrogeomorphology, tilted trees.