Jackson, Ian. Cumbria Rocks — 60 extraordinary rocky places that tell the story of the Cumbrian landscape. Newcastle upon Tyne : Northern Heritage, 2022.
The richly illustrated and accessible book series of Cumbria, Northumberland and Durham Rocks are available to purchase from Northern Heritage.
Theme: Climate and landscape change
39 Helvellyn — aretes and cirques. The summit is a strenuous 7 kilometre return hike from the car parks south of Thirlspot
This is not so much about the top of England’s third highest mountain, more about the ridges that lead to its summit and the tarn that separates them.
Climb all 950 metres of Helvellyn from the east and you will need to scramble along one of two sharp ridges: Striding Edge or Swirral Edge. Both are aretes, the narrow razor of rock left when glaciers carve out the valleys on either side. The freezing and thawing of snow and ice, plus gravity, then sharpen the ridges further. In between these two Edges, lying in a deep bowl, is Red Tarn. In Scotland the bowl would be a corrie, in Wales a cwm, in France a cirque. Red Tarn is typical, it has three steep sides and a low ridge across its fourth side. The bowl it sits in was carved out by snow that turned to ice, which then progressively eroded and deepened the hollow. Aretes and cirques are characteristic erosional features of high mountain landscapes everywhere. The rocks that form the bedrock of Helvellyn are volcanic ash and rock fragments which were erupted 450 million years ago. The glaciers which eroded the aretes and cirques are much younger, less than 2.6 million years old. There have been several Ice Ages during that time; the last major one melted around 15,000 years ago. Then around 12,000 years ago there was a short cold period and small ice caps and glaciers formed again in the Lake District’s high mountains. All these events have cumulatively helped to sculpt the dramatic landscape that we enjoy today.
The crags at the back of the Red Tarn cirque are one of Cumbria’s botanical hotspots, with many montane plants. They include rose-root, mountain sorrel, moss campion and purple saxifrage – particularly where cracks in the rocks have become filled with calcite (calcium carbonate). Helvellyn is probably a Celtic (Cumbric) name meaning pale yellow upland. That sounds right as the top is a flat grassy plateau and not the sharpest summit in the Lake District. But its razor ridges and the panoramic views from its summit make for a great hike.