PHYSICAL GEOGRAPHY 



231 



growth. While plant-growth is abundant in the neighbourhood of 

 the alkaline hot springs, from the vicinity of the sulphur springs 

 it is almost absent. In places where surface-water or underground 

 water is found, mud-holes are formed, or larger or smaller sloughs, 

 in which clayey mud of various colours boils and bubbles; it is 

 sometimes ejected a few feet upwards, whereby crater-like mounds 

 are formed around the larger pits, bearing a weird resemblance to 



Fig. 12. Solfataras of Krisuvik. 



large cauldrons of boiling porridge. The majority of the sulphur 

 springs occur on Reykjanes, in Hengill, near Krisuvik and at Cape 

 Reykjanes where the large slough of Gunna is well-known. More- 

 over, extensive sulphur-spring districts (Namufjall, Krafla, Fremri- 

 namur) occur near Myvatn, and Kerlingarfjoll near Arnarfellsjokull 

 is another, upon the interior plateau. Carbonic acid springs 

 (olkeldur) and Mofettes occur here and there, especially on Snse- 

 fellsnes in western Iceland; the best-known carbonic acid spring 

 is found near Raudimelur in Hnappadal. Ores, metals and stones 

 of any great commercial value are not found in Iceland. Here and 

 there some lignite occurs which is utilized by the neighbouring 

 inhabitants. The gathering of sulphur is no longer lucrative, but, 



