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.
OUTLINE VIEW OF THINGVALLA.
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.