Lysgi was an Irish raider
Geology:-
Porthlysgi Bay has formed through erosion of the heavily sheared Precambrian Volcanic
Tuffs and Ashs seen at the back of bay, and some Head Deposits on the west side
of the bay, which are faulted against the harder rocks to the East and West.
The East side of the bay if formed of Granophyre - a medium grained igneous Microgranite .
Ref: 3407
Date: 12/06/2008
Location: SM 732 235