The different kinds of lava are more fully described in the article Volcano.
Denudation has continued active ever since, and now, owing to greater hardness and consequent power of resistance, the glassy lava stands up as the prominent and picturesque ridge of the Scuir, while the basalts which formerly rose high above it have been worn down into terraced declivities that slope away from it to the sea.
The soil, usually of a reddish-brown colour, is for the most part disintegrated lava mixed with decayed vegetation; occasionally there is also a mixture of disintegrated coral limestone.
The last phase in the history of the Caucasus was marked by the growth of the great volcanoes of Elbruz and Kasbek, which stand upon the old rocks of the central zone, and by the outflow of sheets of lava upon the sides of the chain.
Volcanic activity took place around its shores at the end of the Tertiary or during the Quaternary Age, and great streams of lava cover the Sayan and Khamar-daban mountains, as well as the valley of Irkut.
Ejections of basaltic lava have been observed on the southern slope vo of this range, extending over wide areas on the plateau itself, over a stretch of more than 600 m.
Or more, annually) on the Westward or windward slope, and there they are heavily forested; but the rainfall is light on the eastward slope and the piedmont district is dry; hence the forests thin out on that side of the range and treeless lava plains follow next eastward.
Late in the Tertiary period vast sheets of lava poured from many points of the Great Dividing Range of eastern Australia.
These lava streams, which are of a doleritic character, flowed before the Glacial age, or during its continuance, out of lava cones with gigantic crater openings, such as may be seen at the present day.
A few persons reside on the little island Allegranza, a mass of lava and cinders ejected at various times from a now extinct volcano, the crater of which has still a well-defined edge.