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Det europæiske Nordhav, der 1876. 1877 og 1878
var Gjenstand for den norske Expeditions Undersøgelser,
kan i Udstrækning ikke maale sig med de store
Verdenshave. men det frembyder ved sin Beliggenhed en i flere
Retninger særegen Interesse.
Dette gjælder ikke mindst om dets geologiske
Forhold. Naar vi tager clisse i Betragtning, maa vi kunne
gjøre os et Begreb om enkelty af de Betingelser, der er
givne for Dannelsen af Bundens Afleiringer i dette Hav.
Vi finder det fra forskjellige Sider begrændset af Øer
og Kontinenter, hvor glaciale og vulkanske Kræfter har
været og endnu er i Virksomhed. Norge er vel et af de
Lande, der fortrinsvis har været udsat for Istidens furende
og afgnavende Evne, og Spidsbergen og Grønland befinder
sig endnu i den glaciale Tilstand.
Medens vi altsaa i disse Lande kan iagttage Isens
Virkninger i den nuværende og i den forbigangne Tid, har
vi paa Øerne Island og Jan Mayen de vulkanske Kræfter
repræsenterede i et lignende historisk Forhold. Jan Mayen
er et nedlagt Værksted, hvor der ikke paa mange hundrede
Aar har fundet noget større Udbrud Sted, men Islands
Vulkaner fortsætter fremdeles sin Virksomhed,
Skjønt vi nu vanskelig kan gjøre os nogen Ide om, i
hvör høi Grad de ovennævnte Naturkræfter kan bidrage til
Havets Afleiringer, ved vi dog, at de begge spiller en
medvirkende Rolle. Det er saaledes almindelig bekjendt,
hvorledes Isen — understøttet af Bræelvene — formaar at bære
det Materiale, den har erobret fra det faste Land, ud i
Havet. Her naar den som Drivis ud til de fjerneste Egne.
Det er ogsaa en Nødvendighed, at der ved Vulkanernes
Virksomhed maa samle sig mange mineralske Stoffe paa
Havbunden. At disse kan være af væsentlig Betydning for
dens Afleiringer er — for de store Verdenshaves
Vedkommende — godtgjort ved Mr. Murrays Undersøgelser.
Foruden de oveunævnte Kræfter har vi i Nordhavet
ogsaa andre, der i fremtrædende Grad virker i den samme
Retning. Beeren Eiland er saaledes et mærkelig Exempel
paa, hvorledes Bølgerne til Fordel for Havets Sedimenter
formaar at udgrave og afslide det faste Land.
Ved Betragtning af disse mest iøjnefaldende
Naturforhold kan vi gjøre os et Begreb .om, hvorledes der
udenfra kan tilføres Havet Materiale, men paa den anden Side
ved vi ogsaa, at Dyrelivet ved sine kemiske Virkninger kan
give mægtige Bidrag til de sedimentære Nydannelser.
Hvorledes nu de forskjellige Kræfter virker i Forening, hvem
der har en større og hvem der har en mindre Betydning,
og hvad der er det endelige Resultat af deres Samvirken —
er Spørgsmaal, som vi ikke kan besvare, førend vi har hentet
Materialet til vor Undersøgelse op fra selve Havbunden.
Ifølge Planen for den norske Nordhavsexpedition var
der bestemt, at der paa alle de Stationer, hvor
Dybdemålinger foretoges, tillige skulde optages Prøver fra
Bunden. For at anskueliggjøre de Redskaber, der tjente til
The Seas of Northern Europe scientifically
investigated on the Norwegian Expedition in 1876, 1877, and 1878,
though in point of extent they cannot compare with the
great oceans of the globe, are yet. by reason of their
geographical position, in many respects peculiarly attractive as
a field of exploratory research.
And not least does this apply to their geological
character, which, if rightly apprehended, cannot but afford a
clew to some of the conditions determining the formation
of sedimentary deposit over the bed of the North Atlantic.
The tract in question is bounded on several sides by
islands and continents where glacial and volcanic agency
has been and still continues in operation. Few regions of
our planet can in like degree with Norway have been
exposed to the furrowing and grinding action of glaciers
during the great ice age: - and Spitzbergen and Greenland
are even now in a glacial state.
Thus, whilst the past and present effects of glacial
action may be observed in those regions, the islands of Jan
Mayen and Iceland exhibit a similar historic relation as
regards volcanic agency. The former is, so to speak, a
long since abandoned workshop, in which for hundreds of
years there has been no considerable eruption, whereas the
volcanoes of Iceland continue as active as ever.
Now. though we oan hardly determine in what degree
the said forces tend to increase oceanic deposits, we know
that both play a co-operative part in their formation. Thus,
for instance, it is a well-known fact, that the ice. in
conjunction with glacier torrents, bears down all manner, of debris
to the ocean. From here it find its way as drift-ice to the
most distant regions. Moreover, it is obvious that to volcanic
agency must be ascribed the occurrence of many mineral
substances present in oceanic deposit, of which they are
shown by the results of Mr. Murray’s investigations — as
regards at least the great ocean basins — to-constitute an
important feature.
But. apart from the action of glaciers and volcanoes,
we have other potent forces operating with like effect in
the North Atlantic. Thus, Beeren Eiland signally
exemplifies the remarkable instrumentality of the waves in
accumulating sedimentary deposit over the ocean-bed by
excavating and wearing away the rocks of the shore.
A glance at these salient physical conditions will
suffice to show from what extraneous sources oceanic
deposit can be derived; and on the other hand, we know that
animal life, so abundant in the waters of the sea, must
largely contribute to such new formations. But how the
several forces act in conjunction, what is the product of
each, arid what the joint result of their eo-operation, —
these are questions the bearing of which we cannot venture
to infer till such time as samples of deposit shall have been
brought up from the sea-bed itself.
Pursuant to the Scheme of Work for the Norwegian
North-Atlantic Expedition, a sample of the bottom was, if
possible, to be . obtained at every sounding-station. The
following extracts from "The Apparatus, and how used,’’ one
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