Numerous plugs, small domes and flows are cut and overlie the metamorphic rocks of the Kapsikis Plateau and, according to Gouhier (1978), these form lines along two directions. The plugs are often deeply eroded to form spectacular spines up to 100 m high. Basalt, trachyte and rhyolite are represented, the olivine basalts forming extensive flows and small domes whereas the more evolved rocks form plugs. Four types of trachyte are distinguished by Gouhier (1978) namely biotite, quartz-aegirine, quartz-amphibole and alkaline trachytes, the last consisting essentially of phenocrystal and groundmass sanidine. The quartz-amphibole trachytes also contain aegirine and the amphibole is probably arfvedsonite. Rhyolites may either be cryptocrystalline with mineral phases difficult to distinguish or quartzphyric with acicular riebeckite present as globular structures. Four rock analyses are given by Gouhier (1978).