Acta naturalia Islandica - 01.02.1946, Page 38

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TRAUSTI EINARSSON
of its activity, its discharge consisted mainly of dust and stones”.
(1 c. p. 108 — 9).
In the Faroes 8 or 9 necks are now known and I quote here from
Walker and Davidson’s description of these necks17).
“In most cases the vents are wholly filled with a volcanic ag-
glomei’ate formed of both rounded and angular fragments of basalts
of different petrographic types, frequently scoriaceous and invari-
ably much decomposed, ranging in size from minute particles up to
masses 2 feet in diam. Sometimes the ashes are bedded, dipping to-
wards the middle of the section; sometimes there is no trace of
stratification” (1. c. p. 873).
In the neighbouring and related volcanic series a material has thus
been erupted which is in many respects similar to that of our con-
glomerates, the eruption of rounded blocks being especially inter-
resting.
Of special interest is also a comparison with the volcanic tuffs of
Schwaben in Germany.18) They are very similar to the British occur-
rences and like these are thought to be of purely volcanic (explosive)
origin. But contrary to what appears to have been the case in Bri-
tain they have for some time been considered to be of glacial origin
and only by a thorough research has it been proved that they are
in no way genetically connected with ice. Branco quotes e.g. the
following passage from Deffner: “Den Nachweis, dass auch dort
alle Erscheinungen daftir sprechen, dass Gletscher die vulkanischen
Auswurflinge (des Gebietes von Urach) mit dem anderen Gesteins-
schutt zusammengeschoben und in jenen sonst unerklárlichen
Schutthugeln angeháuft haben .... muss ich mir fur einen and-
eren Ort vorbehalten” (1. c. p. 563). And Branco himself writes:
“Mehr wie einmal ist mir selbst bei der Untersuchung unserer
merkwiirdigen Tuffbreccien, unserer gewaltigen Schuttmassen aus
Weiss-Jura und der durch diese wie jene gebildeten Berge im Vor-
lande der Alb, der Gedanke vor die Seele getreten, ob hier nicht doch
das Werk von Gletschern sich verrate”. (1. c. p. 564). Further
on he asks “ob nicht von den Alpen oder vom Schwarzwald her ein
Gletscher diese Massen gebracht habe, welche hier das Bild nord-
deutscher oder gewisser alpiner Moránen vor seinen Augen auf-
tauchen lassen”. But Branco proves that these masses are purely
volcanic and have in spite of their appearance nothing to do with
ice-work.