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44
I. PHYSICAL GEOGRAPHY OF SWEDEN.
the Scandinavian" mountain chain was formed. Their rocks became, at
j *
the same time, much altered, and the inclosed fossils often completely
crushed and obliterated. Yet, various finds of Silurian fossils as far
up as in northernmost Lappland show that the Cambro-Silurian sea
submerged even those parts of the Scandinavian peninsula which now
rise several hundred meters above the sea. The metamorphosed Silurian
rocks referred to above, consist of many different kinds of mica-and
hornblende-schists, the so-called alpine-schists, comprised under the name
of the Köli-group, or the western Silurian facies of the alpine regions.
The Cambro-Silurian rocks are of great importance for practical
purposes. A light-coloured Cambrian sandstone is quarried and used
for building-material as well as for mill- and grind-stones. A grey,
soft, easily worked Upper-Silurian sandstone in the southern part of
Gotland has been used for many church-buildings in the island. Some
of the Silurian limestones also make an excellent building-stone. For the
burning of lime the limestone and the alum-slate are quarried in many
places in Vestergötland and Nerike, where the bituminous alum-slate
generally serves as fuel in burning the limestone. The burnt
alum-slate was formerly used as raw material for manufacturing alum.
When Sweden had gradually been raised above the sea by which
during the Silurian-period it had been covered, it retained, with the
exception of Skåne, its character as main-land during those
immeasurably long periods when, in other places, thousands of meters of
mighty formations were built up. In connection with the rising of
the land, which undoubtedly required ages for its accomplishment, the
original formation of the Scandinavian mountain-range must have begun
and been finished, while at the same time, in its northern parts, huge
mountain masses of older Precambrian formations were, in the process
of plication, overthrusted and pushed from east to west over the younger
Silurian formations, so that the succession of strata in Areskutan, in
the plateaus of Offerdal, and in many other parts of the eastern
boundary of the alpine regions now appears wholly abnormal, older
formations covering the younger. During the evolutionary period now
considered, the process of general decay, the rushing waters, and other
forces were effective in transforming and leveling the contours of the
surface. Rivervalleys were excavated and extended, plateaus and
mountain ridges were shattered and carried away, and all parts of the
relatively looser Cambro-Silurian formations that had not settled below
the surface of the surrounding Archæan rocks, or been protected by
lava-like coverings of harder eruptive rocks, were destroyed.
The present geological structure of Shine, and the distribution of
its formations, among which the trias-, jura-, and cretaceous systems are
lacking in other parts of Sweden, is chiefly caused by dislocations or
faults. Some faults are of a considerable extent, for example the one
which stretches from the coast at Höganäs in a south-easterly direction
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