Cuillin He partnered Louis Agassiz on his trip to Scotland in 1840 and although they subsequently argued, Forbes went on to publish other important papers on Alpine glaciers. In 1904 Alfred Harker published "The Tertiary Igneous Rocks of Skye", the first detailed scientific study of an extinct volcano. The Cuillin encompasses a wide range of habitats, changing with altitude. At the base there are conifer plantations, coastal woodlands and areas of heather moorland and rough grassland. The lower slopes are covered by various different types of bog, with grassland on the better-drained slopes that are found above 400 m. Higher up,
Geology of Skye Part of the magma chambers for the volcanoes are exposed at the surface as major intrusions of gabbro and granite. These coarse-grained igneous rocks are relatively resistant to erosion and now form the Cuillin hills. The Black Cuillin are formed of gabbro, which erodes to form the characteristically jagged outlines, although this is in large part due to the many minor intrusions, such as dykes and cone sheets that cut the gabbro. The Red Hills are formed of granite and have a more rounded topography. All pre-Quaternary rock types on the island are affected by a major swarm of dykes,