The central band is a mix of volcanic and sedimentary rocks of mid-to-late Ordovician age comprising the lavas and tuffs of the Borrowdale Volcanic Group, erupted as the former Iapetus Ocean was subducted beneath what is now the Scottish border during the Caledonian orogeny. The northern central peaks, such as Great Rigg, were produced by considerable lava flows. These lava eruptions were followed by a series of pyroclastic eruptions which produced a series of calderas, one of which includes present-day Scafell Pike. These pyroclastic rocks give rise to the craggy landscapes typical of the central fells.