Glacial lakeA glacial lake is a body of water with origins from glacier activity. They are formed when a glacier erodes the land and then melts, filling the depression created by the glacier. Near the end of the last glacial period, roughly 10,000 years ago, glaciers began to retreat. A retreating glacier often left behind large deposits of ice in hollows between drumlins or hills. As the ice age ended, these melted to create lakes. This is apparent in the Lake District in Northwestern England where post-glacial sediments are normally between 4 and 6 metres deep.
Balkan MountainsThe Balkan mountain range (Αἵμος, Haemus, known locally also as Stara planina) is a mountain range in the eastern part of the Balkan Peninsula in Southeastern Europe. The range is conventionally taken to begin at the peak of Vrashka Chuka on the border between Bulgaria and Serbia. It then runs for about , first in a south-easterly direction along the border, then eastward across Bulgaria, forming a natural barrier between the northern and southern halves of the country, before finally reaching the Black Sea at Cape Emine.
Rhodope MountainsThe Rhodopes (ˈrɒdəpiːz; Родопи, Rodopi; Ροδόπη, Rodopi; Rodoplar) are a mountain range in Southeastern Europe, and the largest by area in Bulgaria, with over 83% of its area in the southern part of the country and the remainder in Greece. Golyam Perelik is its highest peak at . The mountain range gives its name to the terrestrial ecoregion Rodope montane mixed forests that belongs in the temperate broadleaf and mixed forests biome and the Palearctic realm.
Tree lineThe tree line is the edge of the habitat at which trees are capable of growing. It is found at high elevations and high latitudes. Beyond the tree line, trees cannot tolerate the environmental conditions (usually low temperatures, extreme snowpack, or associated lack of available moisture). The tree line is sometimes distinguished from a lower timberline, which is the line below which trees form a forest with a closed canopy. At the tree line, tree growth is often sparse, stunted, and deformed by wind and cold.
