Fig. 15. Narrow bay on the left side of Segelskar, east of Hango in Finland. The bay owes its existence to the fact that the ice has laid bare a territory coursed through by fissures. Photo by I. I. Sederholm.
Fig. 16. Earthquake centres in Calabria and in Sicily. On the larger map the damaged localities are indicated, on the smaller the most prominent tremor lines. Drawn by I. I. Sederholm.
As a consequence, the fissures on Mars ought to be longer than the corresponding formations on the Earth. A thorough study of the large fissure in Calabria shows that it consists of a veritable network of smaller straight cracks (as is apparent on Figure 16, which is taken from a work by the well-known Finnish geologist Sederholm). On this map the radial cracks (see Worlds in the Making, [Fig. 16]), charted by Suess, are also shown, and their direction under the sea designated by dotted lines. The sketch in the upper left corner of [Fig. 16] is in striking similarity to a picture drawn by Schiaparelli in Mercator’s projection of the planet Mars (see [map] at the end of book). We notice on both, the numerous equidistant lines corresponding to parallel cracks and duplex canals. Not every fissure has its parallel and not every canal its mate—generally only one of the latter is visible and sometimes both disappear.
As the radial cracks in the drawing by Suess if extended meet in the Lipari Islands, so also several canals on Mars run together in a so-called lake (Lowell called them “groves” or “oases”) which evidently is a centre of collapse (many appear on [Fig. 17]). It is plain that all crossings of the “canals” are not necessarily such centres of collapse. (See maps [Figs. 17] and [17a] at end of book).
We shall consequently assume that the canals on Mars correspond to the geological dislocation fissures on the Earth. Along these fissures emerge the gases liberated in the cooling process on both planets; which are similar gases to those which escape through the volcanoes. These vapours are primarily water, next carbon dioxide and, in considerably smaller quantities, sulphuretted gases and hydrochloric acid. They discharge through cracks in regions which, geologically speaking, not so long ago were the scene of volcanic activity. In the dislocation-grooves, lakes, and water courses are often formed, as we may observe in several places in Sweden, for instance near Stockholm.
Assume now a gradual cooling of our earth. Most territories are covered by stratified, comparatively light rocks. To the dislocation fissures water gathers from the surrounding strata and occasionally from the interior, partly washes away the loose material and transforms the fissures into furrows, generally with flat bottoms. Dissolved salts are carried to the sea. As cooling proceeds, the ocean commences to freeze. Each summer the surface melts to a certain extent, as is the case now in our polar regions. Finally, the entire ocean freezes to the bottom, the ice is now to be considered as a kind of rock, flexures and dislocations cease and the ice assumes a smooth surface. In the strong sunlight during the summer this surface thaws, as do the water-courses on the mainland, and these continue to carry their salts to the open surface water. At the approach of winter the latter solidifies again but not as the water in our inland lakes from the top but from the bottom, as ordinary sea-water possesses its greatest density below the freezing point while the opposite is true of fresh water. The consequence is that the ice foundation grows upward and as the surface water becomes increasingly shallow it is turned into a concentrated salt solution. With a further drop in temperature the ice formation is accompanied by crystallization of the salts.
Something similar takes place on the Martian mainland in its flat river basins, which correspond to the salt lakes in our deserts. On account of the bitter cold and the consumption of the water in the process of disintegration (the carbon dioxide has been largely used up in the same manner), precipitation has almost ceased on Mars and most of the water in circulation emerges from the interior of the planet along the fissures. As it contains hydrochloric acid and carbon dioxide it extracts from the soil salts, such as the chlorides of sodium (common salt), of calcium and of magnesium, all present in common sea-water to which it was brought by the rivers. The compounds of calcium and magnesium are not precipitated as carbonated salts through the medium of crustacea as is the case on earth. The strong solar radiation during the summer partly evaporates the water into the thin air, leaving the salts behind. On account of the low temperature, this vaporization on Mars is probably slower than on the Earth. Along the cracks in the crust, a kind of dry salt-lakes are formed similar to the generally shallow and occasionally dry lakes common in the deserts of Central Asia as described by Hedin. We know that Mars possesses a pronounced desert climate. There finally remains in the lowest sections of the water courses a concentrated salt solution, which parts with its water more and more reluctantly, so that the salts which most strongly hold the water crystallize at the deepest points. If the winter’s cold is sufficiently severe (below -55° C. or -67° F.) ice is extracted even from the most concentrated solutions, which mainly contain chloride of calcium. In spite of such extreme temperatures, evaporation into the rare atmosphere is not negligible and the ice crystals partly vanish, to reappear in the coldest regions of the planet, that is, around the pole which at the time is turned away from the sun. On the ocean, now frozen solid throughout, a polar-cap of snow and hoar-frost is formed which finally reaches as far as the 38th parallel on the southern hemisphere (see [Figs. 18] and [19]), where winter occurs when Mars is most removed from the sun, and to the 58th parallel (see [Fig. 19]) on the northern hemisphere where winter reigns while Mars is nearest to the Sun and consequently not quite so cold. Similar conditions obtain on the Earth although not to such a marked degree.
