Greycrag Tarn has largely disappeared under plant life, and there are now only tiny patches of open water. The size of the area of damp plant life suggests that this was once quite a sizeable tarn. Quite what happened is unclear. The 1881-2 Ordnance Survey map shows the tarn as open water, as did Hodgson's 1828 map. However in 1865 it was described as 'almost entirely overgrown' and 'backed by a stretch of most horrible bog'.
This bog grains into Galeforth Gill, which flows down into Longsleddale. At the top of the gill there is a collapsed piece of stonework, with a gap in the middle. To me this looks like an old pack horse bridge on an old forgotten route across the fells, but it could also be an old dam, which would explain the presence of a larger tarn here, if not the purpose.
The bog can be crossed most easily either along the line of the fence to its north, or along its southern edge, although there are some damp patches.
Grid Reference of centre: NY 492 076
How to Reach
The terrain to the north and east of the tarn is generally easy, although lacking paths and with long approach walk requires. The easiest route comes from Sadgill in Longsleddale, where there is a small amount of parking. Climb up the field east of the road, heading for a stile visible in the upper wall. A clear path leads up to a very easy gully, and beyond it another wall. The path runs right along this wall for a short distance then crosses over and heads up Great Howe. A clear path heads along Great Howe towards Tarn Crag and Sleddale Fell. This crosses a fence and then curves away for Sleddale Fell. To reach the tarn leave this path before it begins to curve away to the right and head up a dry gully towards the skyline. This brings us to the eastern edge of Greycrag Tarn's bog.
Currently none of our walks reach Greycrag Tarn
No streams flow into the boggy area.
Galeforth Gill flows south from the bog then turns west to flow into Longsleddale before joining the River Sprint.