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THORODDSEN 



length. Groups of small slag-cones (craters) and lava-kettles (Hornitos) 

 are very common in the lava-fields; they are often gathered together 

 in hundreds upon a relatively small area and without any regularity 



Fig. 9. Lava streams in vertical section (Almannagja). 



of arrangement. These slag-cones are secondary formations, usually 

 associated with lavas which have overflowed marshy ground and 

 lakes, and have therehy absorbed quantities of water-vapour; they 

 are of frequent occurrence near Myvatn, on Reykjanes, and espc- 

 ciallv at Landbrot. 



