Sound Of Barra Integrated Transport Project

Eriskay - Geology

Other rock types include hornblende gneiss, pegmatite and basalt dykes. The hornblende gneiss is dark in colour and occurs as pods and bands within the lighter coloured gneiss. Pink and white pegmatite typically occurs in veins and contains coarse grained quartz and feldspar. Basalt dykes are dark grey, fine grained, later igneous intrusions which can be eroded to form gullies and cliffs.

Rock was also excavated to form the breakwater and create a marshalling area for the ferry terminal on Eriskay at Ceann a Gharaidh. Excavations in this area uncovered shear zones which may be related to the Outer Hebrides Thrust Zone, a low angled fault which trends north to south along the length of the Outer Hebrides. Pseudotachylite has been identified which is formed by the crushing action when rocks are sheared and is also associated with the Outer Hebrides Thrust Zone.

Other rock types include hornblende gneiss, pegmatite and basalt dykes. The hornblende gneiss is dark in colour and occurs as pods and bands within the lighter coloured gneiss. Pink and white pegmatite typically occurs in veins and contains coarse grained quartz and feldspar. Basalt dykes are dark grey, fine grained, later igneous intrusions which can be eroded to form gullies and cliffs.

Rock was also excavated to form the breakwater and create a marshalling area for the ferry terminal on Eriskay at Ceann a Gharaidh. Excavations in this area uncovered shear zones which may be related to the Outer Hebrides Thrust Zone, a low angled fault which trends north to south along the length of the Outer Hebrides. Pseudotachylite has been identified which is formed by the crushing action when rocks are sheared and is also associated with the Outer Hebrides Thrust Zone.