Intermediate volcanic rocks include andesite, dacite, trachyte, and latite. Sanidine is found most typically in felsic volcanic rocks such as obsidian, rhyolite and trachyte. These falls are characterized by its trachyte andesite rocks. Volcanic equivalents would be dacite and trachyte. Rock types include trachyandesite, trachyte, syenite and amphibole - biotite granite. These consist of alkali-feldspar porphyritic quartz-trachyte and trachyte. They are formed of trachyte, dolerite and basalt. The volcanic equivalent of syenite is trachyte. Trachybasalt is a volcanic rock with a composition between trachyte and basalt. These include nephelinite, basanite and peralkaline phonolite, trachyte, and comendite lavas. Lava flows of more viscous phonotephrite and trachyte erupted after the basanite. Its component rock is trachyte and Lower Carboniferous in origin. The island is a volcanic plug of phonolitic trachyte rock of Carboniferous (Dinantian) age. It consists of trachyte of Eocene age. The western wall is made of the trachyte lava dome.