medium-grained igneous rock compositionally equivalent to finer-grained basalt) showing crystals of olivine, that intruded into Carboniferous sediments in the north of the outcrop circa 60 million years ago. At the north end of Murlough Bay, a substantial sill (the Binnagapple sill) appears below the main Fair Head sill, separated by of Carboniferous shales. Despite the thickness, the heat from the Fair Head sill did not alter the underlying Triassic sandstone, however, shales have been converted to hornfels extending up to from the contact. The distinctive columnar jointing of the dolerite rock is the result of stresses caused by the cooling and solidifying of the melt, and there are minor crush zones associated with later compression. Although the cliff face is stable, weathering has periodically toppled some columns producing blocks of massive dimensions on the scree below. Geologists record that even major storms barely disturb these blocks (e.g. unlike the limestone blocks at Ailladie in Clare), and thus the scree may be little changed since the late-glacial period. Rock climbing Reputation and ethics The 2014 Fair Head guidebook, its 6th edition, lists over 430 routes mostly from grade VS 4b up to E6 6b, and the current climbing databases list over 445 routes at grades up to E9 6c. Fair Head is not regarded as an ideal crag for novice climbers, and the long nature of the routes (averaging over 50 metres, with many up to 100 metres), the requirement for long and intimidating abseils for access in many areas, and the high concentration of E-grade climbs, means that it is ideally a crag for intermediate and even more for expert-level climbers. There have been fatalities at the crag. An annual Fair Head Climbing Meet is held over the first weekend of June for all climbers. The cliffs abound in well-protected steep crack climbing, between one and four pitches in length, with routes that range from under to over . Many of the cracks involve hand-jamming (and even full-body jamming), and some climbers tape their hands to protect the skin from the "Fair Head rash". Some routes involve off-width or full-width chimneying, which is not often encountered in other Irish crags. As with all Irish crags, Fair Head is a traditional climbing area with no bolted or sport climbing routes allowed; the Mountaineering Ireland guidebook states that any newly placed manufactured bolts will be removed. Fair Head is considered one of