Roineval

Also within

Ross and Cromarty County

Condition (NatureScot)

Geology & landscape

Geological Period: Paleogene

Landscape processes: Volcanic / Igneous

Description

Roineval Roineval Site of Special Scientific Interest (SSSI) is located in the hills to the north west of Sligachan on the Isle of Skye. The site incorporates the summit area of the hill called Roineval and is significant for the type example of a Palaeogene igneous composite mugearite lava flow which it encompasses. A feature of special petrological interest found in the Skye plateau lava succession is the occurrence of composite lava flows, each of which comprises two distinct members, formed from the almost simultaneous eruption of magma of different composition from within the same magma chamber. Such lava flows are rare and those of Roineval SSSI are regarded as exceptionally fine examples. The upper member contains phenocrysts of plagioclase, olivine and titaniferous magnetite and overlies a largely aphyric mugearite. At this site the boundary between the two members is gradational over several centimetres, contrasting with other similar lava flows in which the two members are separated by a sharp, more clear-cut boundary. Composite lava flows are of scientific interest for the evidence they can provide concerning the changes which can be produced in magma stored beneath a volcano prior to eruption.