The Great Geoadvent: Door 9

Both the granite and slates have been intruded by a dyke swarm (a series of injections of magma) which is slightly younger than the granite and may well originate from a magma chamber not far below the surface 2 to 3 km west of Lundy. The dykes demonstrate increasing fractionation of the magma to dolerites, trachytes and rhyolites. Dykes are clearly visible in places in the cliffs with one dyke forming a face just below ‘Marisco’ Castle.

One very interesting feature of Lundy is the Earthquake, between the island’s Quarter Wall and Halfway Wall, a fissured area which is reputed to have faulted at the time of the Great Lisbon Earthquake of 1755. It is more likely, however, to be the result of mining or possibly of earlier tectonic activity.

Text & image courtesy of Naomi Stevenson.