Borrowdale, walled in part by high, sharp-edged crags, is located in the county’s volcanic central mountains, stretching from the head of Derwentwater south to Seathwaite.
Sty Head Pass connects Wasdale with Borrowdale. Honister Pass connects the Borrowdale and Buttermere valleys. Its glacial lake, Derwentwater, contains four islands – Derwent Island, St Herbert’s Island (named after a hermit who once lived there), Lord’s Island (the site of the first smelter in Keswick) and Rampsholme Island. Derwentwater was once joined to Bassenthwaite Lake until river-borne deposits silted up the section to the west of Keswick. The best way to enjoy Derwentwater is by a cruise on the Keswick Launch. Lodore Falls are an impressive sight after heavy rain, when the waters of Watendlath Beck discharge their load over the edge of the hanging valley, before escaping into Derwentwater.
The valley is distinctive for its “Borrowdale Volcanics‟ which poured (sometimes shot) out of volcanic vents above the Skiddaw Slates in Ordovician times, about 400 million years ago. Silurian slaty beds were then laid down on top of them, these harder Borrowdale rocks have weathered slowly and form crags and precipices above the softer soil-covered sediments to the south and east. The traces of glaciation are very easy to see in Borrowdale; there is a distinctive U-shaped section of the upper dale between Thorneythwaite and Seathwaite. In Langstrath and Greenup Gill there is a great spread of the hummocky moraine of the most recent glaciation. Other parts of the valley include roches moutonées (ice-smoothed rock outcrops), hanging valleys and abandoned erratics (large boulders dumped by the retreating ice). Rosthwaite, is built around a rocky outcrop kown as ‘the How’. Glaciers once gouged their way through the valley, plucking off lumps of rock, polishing exposed outcrops and stripping top soils. When the ice began to melt 10,000 years ago, all this eroded material was dumped in the form of moraines (linear ridges) – at least three have been identified in the Rosthwaite area. Balanced precariously on its small base below the slopes of Kings How, the Bowder Stone (approximately 1900 tons in weight) is a glacial landmark. It was popular with the Victorians, and one bored a hole through the stone. There are now steps to the top and at the bottom it is just possible to shake hands with someone on the other side. The block of stone probably fell from the cliff face.
