High altitude snowy iced lake. A tarn (or corrie loch) is a mountain lake or pool, formed in a cirque excavated by a glacier. A moraine may form a natural dam below a tarn. They are formed when a glacier erodes the land, and then melts, filling the hole or space that it has created. A retreating glacier often left behind large deposits of ice in hollows between drumlins or hills. These lakes are often surrounded by drumlins, along with other evidence of the glacier such as moraines, eskers and erosional features such as striations and chatter marks. Alpine alp climate highland sediment sediments crater mountainous hilly snow ice fly flying glaciation. 4K UHD 3840×2160 30p.