The Chasms, Port St Mary

Dramatic deep fissures in quartz-arenite cliffs — some of the most striking coastal geology in the British Isles. The Chasms formed where the sea has exploited vertical joints in extremely hard, resistant Ordovician rock (quartz-arenite = quartz-rich sandstone). The fissures are tens of metres deep and barely wide enough to squeeze through. WHY VISIT: (1) GEOLOGICAL SPECTACULAR: The rock itself is fascinating — extremely hard white quartzite that has resisted erosion while softer surrounding rocks have been worn away. (2) TRACE FOSSILS: The turbidite sequences (underwater landslide deposits) contain trace fossils — worm burrows, feeding trails, and sedimentary structures that record the seafloor environment 470 million years ago. These aren't showy fossils but they're scientifically valuable. (3) COASTAL SCENERY: Simply stunning. SAFETY: The Chasms are genuinely dangerous — deep, narrow, and with sheer drops to the sea. Stay on marked paths.