Description
Helvellyn in Cumbria is formed from igneous rocks that are part of the Borrowdale Volcanic Group, which includes volcaniclastic sandstone formed from ash and other fragments ejected from the volcanoes that were active in this area during the Ordovician period. Coming from the east the summit is accessed by two knife-edge ridges, Striding Edge to the left and Swirall Edge above Red Tarn. This type of feature, an arete, forms where there are parallel valleys, typically on the northern, and therefore shadier, side of a mountain, places that are ideal for glaciers, which slowly grind the rock to pulp. It is common for these rounded valleys or corries to contain lakes.
