Lord Dufferin, Letters from High Latitudes (1856).

A couple of hours ride across the lava plain we had previously traversed brought us to a river, where our Reykjavík friends, after showing us a salmon weir, finally took their leave, with many kind wishes for our prosperity. Left to ourselves, we now pushed on as rapidly as we could, though the track across the lava was so uneven that every moment I expected Snorro (for thus I have christened my pony) would be on his nose. The scenery of this part of the journey was not very beautiful, the mountains not being remarkable either for their size or shape; but here and there we came upon pretty bits, not unlike some of the barren parts of Scotland, with quiet blue lakes sleeping in the solitude....

After an hour's gradual ascent through a picturesque ravine, we emerged upon an immense desolate plateau of lava, that stretched for miles and miles like a great stony sea. A more barren desert you cannot conceive. Innumerable boulders, relics of the glacial period, encumbered the track. We could only go at a foot-pace. Not a blade of grass, not a strip of green enlivened the prospect, and the only sound we heard was the croak of the curlew and the wail of the plover. Hour after hour we plodded on, but the grey waste seemed interminable, boundless. As it was already eight o'clock, and we had been told the entire distance from Reykjavík to Thingvalla was only five-and-thirty miles, I could not comprehend how so great a space should still separate us from our destination. I put my pony into a canter, and determined to make short work of the dozen or so miles which seemed still to lie between us and the hills.

Judge then of my astonishment when, a few minutes afterwards, I was arrested in full career by a tremendous precipice, or rather chasm, which suddenly gaped beneath my feet, and completely separated the barren plateau we had been so painfully traversing from a lovely, gay, sunlit flat, ten miles broad, that lay -- sunk at a level lower by a hundred feet -- between us and the opposite mountains. I was never so completely taken by surprise. We had reached the famous Almanna Gja. Like a black rampart in the distance, the corresponding chasm of the Hafna Gja cut across the lower slope of the distant hills, and between them now slept in beauty and sunshine the broad verdant plain of Thingvalla.

I could scarcely speak for pleasure and surprise; Fitz was equally taken aback, and as for Wilson, he looked as if he thought we had arrived at the end of the world. After having allowed us sufficient time to admire the prospect, Sigurdr turned to the left, along the edge of the precipice, until we reached a narrow pathway accidentally formed down a longitudinal niche in the splintered face of the cliffs, which led across the bottom, and up the opposite side of the Gja, into the plain of Thingvalla. By rights our tents ought to have arrived before us, but when we reached the little glebe where we expected to find them pitched, no signs of servants, guides, or horses were to be seen.

As we had not overtaken them ourselves, their non-appearance was inexplicable. Wilson suggested that, the cook having died on the road, the rest of the party must have turned aside to bury him; and that we had passed unperceived during the interesting ceremony. Be the cause what it might, the result was not agreeable. We were very tired, very hungry, and it had just begun to rain.

Ages ago – who shall say how long – some vast commotion shook the foundations of the island, and bubbling up from sources far away amid the inland hills, a fiery deluge must have rushed down between their ridges, until, escaping from the narrower gorges, it found space to spread itself into one broad sheet of molten stone over an entire district of country, reducing its varied surface to one vast blackened level.

One of two things then occurred: either the vitrified mass contracting as it cooled, the centre area of fifty square miles burst asunder at either side from the adjoining plateau, and sinking down to its present level, left the two parallel Gjas, or chasms, which form its lateral boundaries, to mark the limits of the disruption; or else, while the pith or marrow of the lava was still in a fluid state, its upper surface became solid, and formed a roof beneath which the molten stream flowed on to lower levels, leaving a vast cavern into which the upper crust subsequently plumped down.

The enclosed section will perhaps help you a little to comprehend what I am afraid my description will have failed to bring before you.
1. Are the two chasms called respectively Almanna Gja, or Main Gja, and Hrafna Gja, or Raven's Gja. In the act of disruption the sinking mass fell in, as it were, upon itself, so that one side of the Gja slopes a good deal back as it ascends; the other side is perfectly perpendicular, and at the spot I saw it upwards of one hundred feet high. In the lapse of years the bottom of the Almanna Gja has become gradually filled up to an even surface, covered with the most beautiful turf, except where a river, leaping from the higher plateau over the precipice, has chosen it for a bed. You must not suppose, however, that the disruption and land-slip of Thingvalla took place quite in the spick and span manner the section might lead you to imagine; in some places the rock has split asunder very unevenly, and the Hrafna Gja is altogether a very untidy rent, the sides having fallen in in many places, and almost filled up the ravine with ruins. On the other hand, in the Almanna Gja, you can easily distinguish on the one face marks and formations exactly corresponding, though at a different level, with those on the face opposite, so cleanly were they separated.
2. Is the sea of lava now lying on the top of the original surface. Its depth I had no means of ascertaining.
3. Is the level of the surface first formed when the lava was still hot.
4. Is the plain of Thingvalla, eight miles broad, its surface shattered into a network of innumerable crevices and fissures fifty or sixty feet deep, and each wide enough to have swallowed the entire company of Corah. At the foot of the plain lies a vast lake, into which, indeed, it may be said to slope, with a gradual inclination from the north, the imprisoned waters having burst up through the lava strata, as it subsided beneath them. Gazing down through their emerald depths, you can still follow the pattern traced on the surface of the bottom by cracks and chasms similar to those into which the dry portion of Thingvalla has been shivered.

The accompanying ground plan will, I trust, complete what is wanting to fill up the picture I so long to conjure up before your mind's eye. It is the last card I have to play, and, if unsuccessful, I must give up the task in despair.

"What's this, Zoega?" I asked.
"Oh, this is the Almannajau."
"What! the great Almannajau, where the Icelandic Parliament used to camp?"
"Yes, sir; you see the exact spot down there below."

And, in good truth, there it was, some hundreds of feet below, in a beautiful little green valley that lay at the bottom of the gap. Never had my eyes witnessed so strange and wild a sight. A great fissure in the earth nearly a hundred feet deep, walled up with prodigious fragments of lava, dark and perpendicular, the bases strewn with molten masses, scattered about in the strangest disorder; a valley of the brightest green, over a hundred feet wide, stretching like a river between the fire-blasted cliffs; the trail winding through it in snake-like undulation - all now silent as death under the grim leaden sky, yet eloquent of terrible convulsions in by-gone centuries and of the voices of men long since mingled with the dust. Upon entering the gorge between the shattered walls of lava on either side, the trail makes a rapid descent of a few hundred yards till it strikes into the valley. I waited till my guide had descended with the horses, and then took a position a little below the entrance, so as to command a view out through the gorge and up the entire range of the Almannajau.

The appended sketch, imperfect as it is, will convey some idea of the scene; yet to comprise within the brief compass of a sheet of paper the varied wonders of this terrible gap, the wild disorder of the fragments cast loose over the earth, the utter desolation of the whole place, would be simply impossible. No artist has ever yet done justice to the scene, and certainly no mere amateur can hope to attain better success.

Looking up the range of the fissure, it resembles an immense walled alley, high on one side, and low, broken, and irregular on the other. The main or left side forms a fearful precipice of more than eighty feet, and runs in a direct line toward the mountains, a distance of four or five miles. On the right, toward the plain of Thingvalla, the inferior side forms nearly a parallel line of rifted and irregular masses of lava, perpendicular in front and receding behind. The greater wall presents a dark, rugged face, composed of immense pillars and blocks of lava, defined by horizontal and vertical fissures, strangely irregular in detail, but showing a dark, compact, and solid front. In places it is not unlike a vast library of books, shaken into the wildest confusion by some resistless power. Whole ranges of ink-colored blocks are wrenched from their places, and scattered about between the ledges. Well may they represent the law-books of the old Icelandic Sagas and judges, who held their councils near this fearful gorge! Corresponding in face, but less regular and of inferior height, is the opposite wall. In its molten state the whole once formed a burning flood, of such vast extent and depth that it is estimated by geologists nearly half a century must have elapsed before it became cool. The bottom of this tremendous crack in the sea of lava is almost a dead level, and forms a valley of about a hundred feet in width, which extends, with occasional breaks and irregularities, entirely up to the base of the mountain. This valley is for the most part covered with a beautiful carpeting of fine green grass, but is sometimes diversified by fragments of lava shivered off and cast down from the walls on either side.

The gorge by which we entered must have been impracticable for horses in its original state. Huge masses of lava, which doubtless once jammed up the way, must have been hurled over into the gaping fissures at each side, and something like a road-way cleared out from the chaos of ruin. Pavements and side-stones are still visible, where it is more than probable the old Icelanders did many a hard day's work. Eight or nine centuries have not yet obliterated the traces of the hammer and chisel; and there were stones cast a little on one side that still bear the marks of horses' hoofs - the very horses in all probability ridden by old Sagas and lawgivers. Through this wild gorge they made their way into the sheltered solitudes of the Almannajau, where they pitched their tents and held their feasts previous to their councils on the Logberg. Here passed the members of the Althing; here the victims of the Logberg never repassed again.

There are various theories concerning the original formation of this wonderful fissure. It is supposed by some that the flood of lava by which Thingvalla was desolated in times of which history presents no record must have cooled irregularly, owing to the variation of thickness in different parts of the valley; that at this point, where its depth was great, the contracting mass separated, and the inferior portion gradually settled downward toward the point of greatest depression. Others, again, hold the theory that there was a liquid drain of the molten lava underneath toward the lake, by means of which a great subterranean cavity was formed as far back as the mountain; that the crust on top, being of insufficient strength to bear its own great weight, must have fallen in as the whole mass cooled, and thus created this vast crack in the earth.

I incline to the first of these theories myself, as the most conformable to the contractile laws of heat. There is also something like practical evidence to sustain it. A careful examination of the elevations and depressions on each wall of the gap satisfied me that they bear at least a very striking analogy. Points on one side are frequently represented by hollows on the other, and even complicated figures occasionally find a counterpart, the configuration being always relatively convex or concave. This would seem to indicate very clearly that the mass had been forcibly rent asunder, either by the contractile process of heat, or a convulsion of the earth. The most difficult point to determine is why the bottom should be so flat and regular, and what kept the great mass on each side so far intact as to form one clearly-defined fissure a hundred feet wide and nearly five miles in length? This, however, is not for an unlearned tourist like myself to go into very deeply.

How many centuries have passed away since all this happened the first man who "gazed through the rent of ruin" has failed to leave on record - if he ever knew it. The great walls of the fissure stood grim and black before the old Icelandic Sagas, just as they now stand before the astonished eyes of the tourist. History records no material change in its aspect. It may be older than the Pyramids of Egypt, yet it looks as if the eruption by which it was caused might have happened within a lifetime, so little is there to indicate the progress of ages. I could not but experience the strangest sensations in being carried so far back toward the beginning of the world.

At the distance of about a mile up the "Jau" a river tumbles over the upper wall of lava, and rushes down the main fissure for a few hundred yards, when it suddenly diverges and breaks through a gap in the inferior wall, and comes down the valley on the outside toward the lake. During my stay at Thingvalla I walked up to this part of the Almannajau, and made a rough sketch of the waterfall. From the point of rocks upon which I stood the effect was peculiar. The course of the river, which lies behind the Jau, on the opposite side, is entirely hidden by the great wall in front, and nothing of it is visible till the whole river bursts over the dark precipice, and tumbles, foaming and roaring, into the tremendous depths below, where it dashes down wildly among the shattered fragments of lava till it reaches the outlet into the main valley. A mist rises up from the falling water, and whirls around the base of the cataract in clouds, forming in the rays of the sun a series of beautiful rainbows. The grim, jagged rocks, blackened and rifted with fire, make a strange contrast with the delicate prismatic colors of the rainbows, and their sharp and rugged outline with the soft, ever-changing clouds of spray.