Easedale Tarn in the English Lake District. Easedale Tarn is one of the larger tarns in the district, about 480 metres long and 300 metres wide. Its outflow is Sourmilk Gill, named after the milky white colour of its waterfalls, which runs east towards Grasmere. The gill displays impressive water scenery when seen from Grasmere, and from the path to the tarn.The tarn is a popular destination for walkers. Many people climb the path from Grasmere which overlooks Sourmilk Gill.