which has erupted no less than fifteen times since the year 900.
It now presents nothing but a deep valley filled with snow, cutting
into the very heart of Myrdals Jökull; it is one of the largest
examples of breached craters in the world. The principal phenomena
attending eruptions of this volcano are stupendous floods of heated
water and the prodigious quantities of sand ejected. It has, I
believe, never been known to produce lava, but upon the base of the
mountain I found numerous ancient lava streams, proving that at
one time Kötlugiá was no exception to its neighbouring volcanoes.
The floods from Kötlugiá during eruptions have often submerged a
district of 280 square miles, continuing sometimes for days, in
spite of the rapid outflow to the sea. These floods are produced
not only by the melting of the snow at the time of eruption,
but in all probability by the bursting of large cavities in and
beneath the mountain, in which water might have been for years
accumulating. This aqueous phenomenon is, however, by no means
peculiar to Kötlugiá, although it occurs on the largest scale,
for during the 13th and 14th centuries all the volcanoes in the
south of Iceland erupted water. The most extensive eruption that
ever occurred in Europe during historic times proceeded from the
south-west portion of the Vatna, named the Skaptar Jökull. This
volcano has only been known to have erupted upon that occasion,
viz., A.D. 1783, when it produced two of the most extensive lava
streams in Europe. The highest volcano in Iceland is Örœfa Jökull,
which reaches the height of 5927 feet.
The volcanoes which erupted so violently in the spring of 1875,
and one of which wrought such damage in the north of Iceland,
are--the Öskjugjá (or the chasm of the oval casket), situated in
the Dyngjufjöll mountains upon the north of the Vatna, and a chasm
some twelve miles in length, which opened in the Mývatns Örœfí (or
sandy desert of Mývatns), but as these have already been described
at some length I need only casually mention them.
Having briefly enumerated the more important volcanoes of
Iceland, we will now consider their products. First there are
the agglomerates, which form such an important feature in the
geology of Iceland, formed either directly by debacles at periods
of eruption, or indirectly by streams and atmospheric influences.
Secondly we come to the lavas; these occur either as stony streams
that have flowed from the volcanoes, or as pumice which has been
hurled high into the air and fallen in a destructive shower of
vesicular cinders. Another class of lavas we must likewise mention,
namely, the glassy, but we must for the present confine ourselves
more particularly to the physical geology of Iceland, leaving the
character of the Icelandic rocks for other consideration. Of the
stony streams of lava we have two very good examples; first, the
huge lava streams which flowed from Skaptar Jökull in 1783, being
50 miles long and 15 wide; and the other 40 miles in length and
seven broad, being in some places 500 feet in depth. It has been
computed that the entire mass exceeds in bulk that of Mont Blanc.
This lava is basaltic and highly ferruginous, and impregnates very
strongly the waters of the river Eldvatn, which flows through
it. The second example is the lava stream which has flowed into
the far-famed valley of Thingvellir, wherein the Althing, or
Parliament, of Iceland used to hold their meetings, and the
wonderful rifts of the Almanna-gjá and the Raven’s-gjá occur. At
some remote period of the geological history of Iceland a large
river of lava flowed from Mount Skjaldbreið, which is about thirty
miles distant, into the valley of Thingvellir; a crust, of course,
soon formed on the surface, and upon the cessation of the eruption,
the still liquid lava at the bottom of the stream continued to flow
into the deeper parts of the lake which occupies the south-east end
of the valley of Thingvellir, leaving the unsupported crust, which
was now of great thickness, to sink down to the present level
of the valley, occasioning lateral rifts upon either side of the
stream, viz., the Almanna-gjá on one side, and the Raven’s rift
upon the other. The valley of Thingvellir is likewise traversed
by many smaller fissures and crevasses, which in many instances
enclose and almost inosculate large masses of lava; the Lögberg,
or “hill of laws,” is such an island of rock, and is rendered
inaccessible, except at one point, by deep yawning crevasses. It
was on account of these natural fortifications that it was chosen
as a forum for the ancient court of Althing, which assembled there
once a year. Such are the monuments of Iceland, which take the
place of the ruined castles and abbeys of other countries, simply
the rude rocks of nature ennobled by brave deeds of history or some
touching romance of love.
We now come to the hot springs of Iceland. The chief of these,
_par excellence_, is, of course, the Great Geysir; it has been so
often described and re-described that it scarcely needs a remark
from me. Professor Forbes calculated its age, from the thickness
of the siliceous sinter which surrounds its basin, at 1000 years.
The Great Geysir is surrounded by numerous other springs of all
temperatures and sizes, whose deposits differ according to the
character of the rocks through which they pass. There are numerous
hot springs scattered about in various parts of Iceland, some of
which owe their existence to earthquakes, which instantaneously
called them into being--in 1339 a hot spring sixty feet in diameter
suddenly opened at Mosfell--and during the earthquakes which
preceded the great eruption of Skaptar Jökull in 1783, no less
than thirty-five new hot springs made their appearance. We may not
dwell longer upon these interesting phenomena, but we will turn our
attention to the huge ice mountains or Jökulls of Iceland, which
constitute such an important feature in the physical geography of
the country. The principle ones are the Vatna, Arnarfells, Hofs,
Lang, Myrdals, Godalands, Eyjafjalla, Dránga, and Glámu Jökulls. Of
these remarkable features in the physical geography of Iceland we
could not find a better example than the Vatna Jökull, which has
formed the principal subject of this little book: until recently it
was almost a _terra incognita_, and until this year had resisted
all attempts to cross it.
The Vatna Jökull is a vast accumulation of volcanoes, ice, and
snow, comprising an area of over 3000 square miles. It is for the
most part surrounded by a wilderness, formed by the destructive
outbursts of its volcanoes, and the constant drifting of the
glacial torrents which flow from its melting snows. The Vatna
Jökull and its immediate surroundings constitute the most lofty
portions of Iceland, and I believe the oldest, for we find lava
streams which have flowed from its volcanoes in a state of ruin
and decay unequalled in any other part of the country; and, again,
we find it bounded upon the south by sea cliffs that were washed
by pre-historic oceans when many other parts of the island must
necessarily have been under water, unless very serious depressions
have taken place since the waters which washed the south outlying
hills of the Vatna receded to their present limit. The Vatna
Jökull comprises by far the most important mountain section in
Iceland, and a far greater area is covered by its snows than could
be occupied by the sum of all the remaining snow-clad mountains
in Iceland. As may be supposed, perhaps half the river water of
Iceland flows either directly or indirectly from the Vatna Jökull,
either issuing in torrents from the extremity of its glaciers, or,
after filtering for long distances through the loose and cavernous
ground, appearing as land springs at a lower elevation. The rocks
of the Vatna, as far as I have had an opportunity of judging, are
purely and simply the product of this very remarkable cluster of
volcanoes, which have piled up layer after layer of ash, sand, and
agglomerate, until a mountain heap was formed of such a height that
it allowed snow and ice to accumulate upon it to such an extent as
to render the summer’s warmth quite inadequate to remove it. This
vast snow pile then grew of its own accord, and glaciers commenced
to creep down the sides of the barren mountains upon which it
rested. Volcanoes continued to erupt, but the effect of their fires
upon the accumulating snow must have been purely local and limited
in the extreme; for volcanic productions are the worst possible
conductors of heat, and I should imagine that a lava stream,
unless it be of gigantic proportions, conducts itself beneath the
profound snows of the Vatna much as a lava stream would beneath
the sea, without producing any very violent commotion. Thus this
vast mountain mass was accumulated, growing with each succeeding
winter and each eruption. The Vatna Jökull rises by a very gradual
slope upon the south, and it is not until more than thirty miles
of snow fields have been traversed that the highest part of the
Vatna, viz., 6,150 feet, can be reached from that direction. I
have at present omitted any mention of the snow line in Iceland;
this is on account of its variable nature, incidental to local
causes. Thus upon the Vatna we have the snow line much lower upon
its southern than northern slopes, the cause of which we will
consider presently. Of late years the volcanic forces of Iceland
appear to have retreated to the Vatna Jökull and its immediate
neighbourhood, and volcanic eruptions have been witnessed in force
in several directions. The Kverkfjall we found to be smoking and
Öskjugjá can only be regarded as a lateral crater of the Vatna,
and, I doubt not, had we been favoured with better weather, we
should have found many other eruptive vents; but so rapid is the
accumulation of snow upon the Vatna, and so bad a conductor of heat
are all volcanic eruptions, that the traces of them are very soon
obliterated. As may be supposed, such a prodigious accumulation
of ice and snow as the Vatna Jökull produces a very sensible and
marked effect upon the climate of certain parts of Iceland. It has
this effect--it deluges the country to the south of it with rain,
and gives to those districts which lie to the north of it a happier
climate than they would otherwise possess. The snowy heights of
the Vatna attract to themselves the aqueous vapours which travel
northwards from more southern latitudes, depositing them upon their
broad shoulders in the form of snow and hail, and refrigerating and
drying the vapours which travel across their snows, thus rendering
the south wind a wet one in the country to the south of the Vatna
and the north wind a dry one, whilst in those districts which
lie to the north of it the reverse is the case. And since by far
the greater part of the aqueous vapours which reach Iceland are
borne thither from the more readily evaporating waters of southern
oceans by that bugbear to travellers in the south of Iceland, the
southerly wind, we see at once why the snow line is lower upon
the south than the north of the Vatna Jökull. When we inspect the
glaciers which fringe the south of the Vatna Jökull, we find they
have decidedly advanced; indeed, at one point so much so as to
almost destroy communication along that part of the south shore.
Upon the north we find that a huge tongue of glacier has flowed
down full ten or twelve miles beyond the utmost limit assigned to
it by Gunnlaugsson some forty years ago, while the route traversed
by that enterprising man is completely overrun by the ice, and the
traditionary road of the Vatna Jökull’s verge is now amongst the
high snows of the Vatna. Icelanders, as a rule, are loth to admit
the advance of their glaciers, and vainly appeal to striated rocks
at much lower altitudes than most of the Icelandic glaciers of the
present day, and to moraines stranded upon the plains beneath some
of the principal mountain sections; but since it is impossible
to say when these rocks were scratched, or even whether the very
rocks to whose striæ they so confidently point were not erupted
long before Northern Europe and America disappeared beneath the ice
and snow of the earlier glacial period, what is the use of such
evidence? The very moraines may have been produced by the glaciers
which have strewn even our own country with erratic boulders and
glacial _débris_. Again, it is no uncommon thing in Iceland for
huge masses of glaciers to slide down the mountain side during
periods of eruption, scratching the harder and furrowing the softer
rocks in their progress, and leaving heaps of _débris_ in no way
distinguishable from terminal moraines. These facts are rather
startling. True, the glaciers of Iceland may, and, no doubt, do ebb
and flow, but they gain upon the whole, and never would increase
to this extent was not the annual accumulation vastly in excess of
the waste. It may be said this is due to a cycle of unpropitious
seasons. Possibly; but we find this advance of northern glaciers is
not peculiar to Iceland. Dr. Nordenskjöld has proved a considerable
advance in the glaciers of Spitzbergen; Greenland gives us the same
intelligence. This seems to point to something more than a local
advance, compensated for by a retreat in other places. It is too
rapid an advance to be accounted for by astronomical causes; but
cannot we suggest some comparatively slight physical changes which
may account for it? Granted that above a certain latitude the earth
only receives as much heat during the summer as it does during the
winter, and that in one winter it will accumulate just as much
snow and ice as the summer’s heat will suffice to melt, if it were
all employed for that purpose. Now we are perfectly aware that snow
and ice having once accumulated, a greater part of the succeeding
summer’s heat would be reflected back into space and not employed
in melting them, while the aqueous vapours condensing above it
would screen the snow from solar influence. Thus a new glacial
period would creep upon us, heralding its approach by an advance
band of low temperature of its own production were it not for the
warm oceanic and atmospheric currents, for the beneficial influence
of which we have only to look at the varying temperature of many
localities in similar latitudes to appreciate. A great alteration
in temperature and climate would certainly take place supposing
any variation should occur in the direction of these currents--in
the Gulf Stream, for instance. Supposing that its waters, instead
of reaching so far north, were deflected southwards, then not
only would Arctic climates and Arctic ice be less affected by it,
but the deflected stream would heighten the temperature of the
waters of lower latitudes, and cause an increased evaporation;
consequently there would be an increased condensation upon northern
mountains and Polar shores, and an increased reflection of the
succeeding summer’s sun. It is rather a curious fact that less
American driftwood has been brought to the northern shores of
Iceland during late years, and an increased amount has been cast
upon its southern coast. This little fact of course proves nothing
in itself; but when we see northern glaciers advancing to the
extent they have done one naturally asks the reason. Astronomical
causes we must put on one side, for the glacial advance is too
rapid to admit of that solution. But if northern glaciers continue
to advance, it will be a matter of some interest if we could
ascertain whether those mysterious forces which give birth to the
earthquake and the volcano have wrought any alteration in the flow
of that guardian angel of the north--the Gulf Stream.
We will now pass on to the volcanic rocks of which Iceland is
constituted. The foundation of Iceland is palagonitic tuff of
sub-aqueous origin, disturbed and at times metamorphosed by
enormous masses of amygdaloidal basaltic lava whose cavities abound
with zeolites, being traversed by dykes and layers of interjected
basaltic and trachytic lava at all times dislocated and confused by
the various earthquakes which from time to time have shaken Iceland
to its nethermost stone. These rocks are overlaid by lava streams
of sub-ærial origin, pumiceous tuffs and agglomerates that have
been formed by debacles and atmospheric influences. Concerning
the strike and dip of the various layers of trap and basalt there
is no general inclination, no uniformity--all is confusion. The
loose soil of Iceland is entirely composed of disintegrated and
decomposed volcanic rocks and decayed vegetable matter, and would
be very fruitful if it were in a lower latitude. The vast period
of time which it must have taken to decompose the huge lava
streams that we find almost entirely converted into humus may be
appreciated when we look upon pre-historic lava fields, grey with
lichens, like that of Thingvellir, while the actual decomposition
of its surface scarcely amounts to half-an-inch. We may divide the
lavas of Iceland, like those of most other volcanic districts,
into two classes; first, the basalts passing into dolerites, and
secondly, the trachytic lavas. The more ancient basalts occur
most frequently as intruded masses of amygdaloidal character; the
doleritic lavas of Iceland are the more recent products of its
volcanoes, varying only in this respect, that the earlier erupted
lavas contain crystals of olivine, in addition to the felspar and
augite which occur in most of the lavas of our own time.
Trachytic lava occurs but sparingly in the parts of Iceland that I
have visited. It has for a long time been assumed that a trachytic
band was disposed upon a fissure which bisected Iceland from N.E.
to S.W., namely from Cape Langanes to Reykjanes upon which the
principal centres of eruption were supposed to be situated. This,
however, is a presumption unwarranted by investigation. A glance at
the map will show us that there are many other centres of volcanic
activity which do not occur in this imaginary trachytic band.
True most of the more recently active volcanoes occur upon this
rectilinear, but there are Myrdals Jökull, Eyjafjalla and Örœfa
Jökull, all volcanoes that have erupted comparatively recently, and
a host of more ancient volcanoes distributed over other portions of
the island, which might lead us to surmise that there were a dozen
instead of one great fissure in the superficial rocks of Iceland.
Trachytes, principally I believe in an altered condition, have been
found around and between Hekla and the Geysers, and notably at the
volcano of Rauðarkamb. I was informed, however, that we must look
for the greater part of the trachyte of Iceland other than in a
pumiceous form upon the peninsulars of Snæfells Jökull. Certainly
I found that trachytic lava almost died out upon the north side of
the Vatna Jökull, or else it is so covered up with recent volcanic
productions as to be undiscernible. The obsidians of Iceland, which
are found so universally distributed in fragmentary forms upon the
sides of the volcanoes are seldom to be met with _in situ_, indeed
the only instance that I have met with of obsidian _in situ_ was at
Mount Paul, in the heart of the Vatna Jökull. That mountain, as we
have already seen, is entirely composed of obsidian, varying from
the vitreous to the grey stony variety.
The obsidians of Iceland seldom contain the beautiful felspar
crystals, so characteristic of the Arran pitch-stones, but some
of them are of a porphyritic nature, showing under the microscope
crystals of quartz much fissured and split about, no doubt during
the process of cooling. We must also regard the greater part of
the pumice which was ejected last year from the Öskjugjá as an
obsidian, in spite of its remarkably vesicular character. The
fine dust which was carried to Norway during the eruption of last
Easter-day resembled powdered glass, and led geologists there to
come to the conclusion that the mountain which was erupting must
have been pouring out great quantities of obsidian. As compared
with the lavas of Vesuvius, I cannot help suggesting that many of
the more ancient lavas in both instances are of a more trachytic
and porphyritic character. In the Vesuvian lavas especially, the
crystals contained by the older rocks have crystallized out of the
uncrystalline or semi-crystalline mass. A prevalent mineral in the
older Vesuvian lavas is leucite, which corresponds to the olivine
that occurs so frequently in the older erupted lavas of Iceland,
while those minerals are seldom to be met with in the more recent
lavas of either Iceland or Italy.
I must now bring these few pages to a close. I dare say they
contain a great deal of what is not worth reading; but as they give
the only account of the Vatna Jökull and the part of the Ódáðahraun
which I traversed, I trust those that may take the trouble to read
them, will accept them as the best and the most accurate account of
those districts that I am able to give.
INDEX.
PAGE.
Agglomerates 183
Akreyri 143
Alderjufoss 159
Arnarfell-hið-Mikla 166
Ásberg 136
Askja, plain of 86
Birch-tree 20
Borðeyri 138
Breiðamerkr Glacier 17, 24
” ” Sandr 23
Climate 180
Crater Lakes 122
Dettifoss 119
Dyngjufjöll 83
” ascent of 101
Equipment 28
Eyrarbakki 8
Glaciers 190
Grafalandá River 76
Grímstaðir 70
Heiði 11
Hekla 181
Hengill, volcano of 6
Herðubreið 65, 103
Hot Springs 185
Hraun 7
Hrossaberg 75
Húsavík 133
Iron Pyrites, sublimation of 174
Jökulls 186
Jökulsá-á-fjöllum 61
Kaldbakkr 14
Kálfafellsfjall 30
Kálfafellstaðr 25
Kiðagil 160
Kistufell 54
Kötlugiá 181
Krafla 123
Lœkjarbotn 5
Lake Grœnavatn 126
” Mývatn 111
Lavas of Iceland 183, 193
” ” Mývatns Orœfí 108, 155
Laxá River 131
Lindá River 77
Lómagnúpar 19
Mount Paul 36
Mud-pools 115
Mývatns Orœfí, eruption of 146
Námufjall 113
Núpstað 15
Núpstaða-skógr 21
Núpsvatn River 18
Obsidian 36, 124
Ódáðahraun 95
Ölfusá, river of 8
Öskjugjá, crater of 88
” volcano of 84
Pemmican, preparation of 26
Perlite 38
Provisions 29
Pumice 63, 78
Querkfjall 63
Reykjahlíð 112
Rivers, diversion of 57
Seljalandsfoss 13
Shark-liver oil 144
Skeiðarár Sandr 18
Skjaldbreið, ascent of 83, 96
Skjálfandifljót 145
Skógarfoss 11
Snow, camping in 32
Solfataras 174
Spherulite 38
Sprengisandr 165
Storms on the Vatna 46
Sulphur mines 112, 129
Svartfugl 23, 25
Swans 13
Thjórsá 10, 167
The “Great Kettle” 129
Trachytic lava 170
Vaðalda Hills 61
Vatna Jökull 32, 186
” ” Housie 41
Volcanic mud 84, 88, 92
Water, eruption of 89
FOOTNOTES:
[1] So called from a particular kind of bird, called Lómi,
which frequents this mountain.
[2] Not marked on the map.
TRANSCRIBER’S NOTE
For consistency all occurrences of a.m. and p.m. have been changed
to A.M. and P.M.
Icelandic names often have accents and hyphens, but they are applied
inconsistently in the original text. Names in the etext have
been adjusted to be consistent and follow the most common variant in
the text. For example Reykjahlid, Reykjahlið, Reykjahlíð, have all
been rendered as Reykjahlíð.
Five occurrences of Öskjagjá have been changed to Öskjugjá.
Eight occurrences of Dyngjufjall have been changed to Dyngjufjöll.
Seven occurrences of Reykjahlaíð have been changed to Reykjahlíð.
Obvious typographical errors and punctuation errors have been
corrected after careful comparison with other occurrences within
the text and consultation of external sources.
Except for those changes noted below, all misspellings in the text,
and inconsistent or archaic usage, have been retained: for example,
sandbank, sand-bank; mid-day, midday; grass land, grass-land;
under weigh; negociated; felspar; enwrapped; indurated; coign.