The Botany of Iceland - 01.12.1914, Blaðsíða 66

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THORODDSEN
often occurs above the clay, and then more recent river-deposits,
alternating with móhella, volcanic gravel, etc. Here and there, these
formations are exposed at the surface and form an almost barren
gravelly ílat (melar), which, far into spring, is quite slushy, owing
to the melting snowr, whicli cannot drain away on account of the
sub-surface ice and the clayey subsoil. In tlie eastern part of the
southern lowland tract, under the boggv ground, occur enormous
river-deposits (Landejqar) — delta formations from Markartljót and
other rivers. But higher up, where the soil is drier (Rangárvellir),
the subsoil is composed of thick móhella-formations; nearer to the
sea occur fine sand and downs.
In several districts in the lowlands there are a great many
rocky ridges (holt), which protrude through the morasses and grass-
land. They vary in nature according to the character of the underlying
rock, and generally consist of hasalt or dolerite, rarely of palagonite-
breccia. These ridges usually bear clear evidence of the action of
the glaciers during the Ice Age. Thev are highly ice-striated and
often have two distinct sides, one bearing traces of having been
exposed to the direct force of the ice, while the leeward side is
comparatively destitute of such marks. Their external form is some-
times dependent upon the direction of the inclination of the basalt-
layers. In some places (Mýrar and Breidifjörður) they originate from
fragments of a deeply sunk basal rock. The surface i's usually stony,
with solid rocks, larger loose stones, and smaller gravel; sometimes
a great many erratic blocks are scattered upon the ridges. As re-
gards plant-growth, these ridges should be characterized as rocky
flats more or less covered with vegetation, and protruding like small
islands above the grass-covered, usually boggy level lands. In several
places the ridges, in olden times, have been clothed with coppice
woods, but it is centuries since the coppice has been destroyed bjr
sheep and goats. Such ridges are found scattered over a great part
of the island in the lowlands and valleys, and often impart a cha-
racteristic feature to the landscape. The farm-buildings are often built
upon them. In the low-lying marshy land of Mýrar, at the edge of
Faxaflói, they occur scattered in hundreds in the bogs, and in the
southern lowland district they are frequent in the eastern part of
Flói and the upper part of Holt, while elsewhere large stretches of
this lowland area are completely ílat. In other districts they are
so large that they are most properly described as small moun-
tains (fell, hálsar). In the valleys the old moi-aines are often trans-