Where lava has been piled up in successive nearly horizontal sheets, with occasional layers of tuff or other softer rock between them, it offers conditions peculiarly favourable for the formation of escarpments, as in the wide basalt plateaus of the Inner Hebrides.
The rocks on the verge of the Kisumu province of East Africa are mainly volcanic (basalt, tuff, lava, kenyte).
Like the rest of the cluster, the island is of volcanic origin, with tuff, trachyte and obsidian among its ordinary rocks.
In the Rudolf province there and are the basalt, lava, tuff and kenyte of the volcanic mineralogy.
The lavas are usually porphyrites, which occur in sheets, with intercalated bands of volcanic tuff that are sometimes strongly felsitic. One of the vents by which such materials were ejected occurs in the Braid Hills on the south side of Edinburgh.