388 Leonard Hawkes—Buirlding up the North Atlantic 
ANALOoGoUS Deposits or tHE Moprern Lava Deserts. 
There is no region which better illustrates the conditions under 
which the greater part of the Tertiary volcanic series of the North 
Atlantic lands was built up than the great Oda%ahraun desert which 
stretches in a northerly direction from the Vatna Jokull, and covers 
an area of over four thousand square kilometres. It is a plateau of 
lavas, a stony sea out of which the tuff cones loom like islands. 
Many of the flows have a ropy surface (see PI. XVI, Fig.22): 
I have never seen such surfaces in the Tertiary series of Iceland, 
nor do they seem to have been noted in the British Isles—the fact is 
a curious one. : 
In the summer of 1914 a journey was made across the Oda%ahraun 
to the Askja crater, and four circumstances were noted which have 
a bearing on the problem of the red partings. These are: (1) the 
fresh and unweathered nature of the lava surfaces; (2) the almost 
complete absence of plant and animal life; (3) the lack of water; 
(4) the dust-storms. The freshness of the surfaces of lavas, the 
outpourings of which we have no historic mention of, was evidenced 
by the sound metallic clang of the horses’ hoofs as they picked their 
way over the uneven ground. The rough (aa) lava surfaces also 
showed very little evidence of any chemical denudation, though 
where markedly cindery some mechanical weathering down had 
produced a black sand. I saw no sign in the Oda%ahraun or in the 
wastes to the east of Namufjall, Myvatn, of any weathering of lavas 
giving a product comparable with the red partings. ‘The only 
equivalent to the latter were the loose fragmental deposits of volcanic 
ash and sand which covered certain areas. When at rest these 
deposits are a great boon to the traveller enabling him to make 
fairly rapid progress over ground that would otherwise be impassable, 
but they are greatly dreaded when winds arise, being caught up and 
carried forward as a brown dust cloud. Even in the houses bordering 
the desert, though door and window be carefully barred, still the fine 
particles make their way into the room. To quote from Thoroddsen : 
‘¢ Blown sand is of varied quality and origin. It may be coarse or 
finer; it is sometimes so fine that it penetrates everywhere. During 
violent storms in sandy districts the fine dust is carried to the most. 
remote quarters of the island and is deposited as a fine layer all over 
the surface; it even falls on vessels in mid-Atlantic. But naturally 
most dust falls in districts bordering on the tuff-belt or situated in 
it, as the dust chiefly originates from the tuff. The atmosphere 
in distant regions is often yellowish brown because of the fine dust 
suspended in the air, and this dust cloud is known in Iceland as 
‘mistur’. This tuff dust has played a very important part in the 
formation of the Icelandic soil and subsoil, and it can be demonstrated 
almost everywhere’? (5, p. 243). . 
Tuer INTERPRETATION OF THE Rep PaArtINGs. 
It seems that these fragmental deposits are the equivalents of the 
majority of the red partings, and that these latter do not represent 
weathered lava-flows. This conclusion has been felt hard of 
acceptance by some who have been impressed by the lack of 
