A low-level circuit through the Pentland Hills, taking in a range of geology and landscapes.

THE ROCKS: The rocks of the Pentland Hills were formed during volcanic eruptions around 400 million years ago. This low-level circuit of Black Hill takes us through a range of rock types and landforms that show how the Pentlands have been constructed and eroded. We will explore a variety of igneous rocks, formed by volcanic activity during the early Devonian period, around 400 million years ago. The rocks include andesite and microgranite, and they have been affected by a long history of deformation and uplift since they formed. We also get a glimpse beneath the volcanoes, to much older rocks formed on a vanished ocean floor.

THE WALK: From Threipmuir, we will climb towards Bavelaw and take a low-level route through the valley to the south of Black Hill. We then pick up the good track alongside Loganlea Reservoir and leave this before reaching Glencorse to take another valley route back across to Threipmuir and return to the start point. Total distance 12km. This is classified as a Moderate Walk: not always on paths, may be rough or slippery underfoot at times. It may be wet, windy and cold. Come equipped with strong footwear, good waterproof clothing, something to eat and drink.

MEETING POINT & ROUTE: Red Moss car park, south of Balerno. Grid reference: NT166638 | Nearest Postcode: EH14 7JT | What3Words: pioneered.script.fresh | Route Map.