Ein Wort über den Sitz der vulkanischen Kräfte in der Gegenwart (Mittheilung aus dem Museum für Volkerkunde zu Leipzig)

Abstract

As such a difficult subject cannot be discussed in a short, notice, it must suffice to give the author's conclusions, tie regards the globe as originally a liquid mass, which has become incrusted through loss of heat. This crust at first would be thin and incapable of offering an effective resistance to the struggles of the liquid interior. It would be ruptured at countless points, great floods of lava would be outpoured, without, however, the building up of important volcanic hills. At this epoch the earth may have even been surrounded by a photosphere. In the second stage the crust layer thickens to about 10 kilometres—the phenomena are similar in kind, but correspondingly reduced in extent. In the third stage the crust layer is about 25 kilometres, and the places of discharge from the liquid interior are fewer. Eruptions come from local reservoirs in the generally solid crust, which, however, may have a communication from beneath with the inner mass. In the fourth stage, when the;rust layer approaches 50 kilometres, there is a further decline in number, though an increase in violence, of discharges from the liquid interior, but the activity of the reservoirs is maintained, and henceforth these are the main sources of vulcanicity. That is the age of catastrophic eruption, and the photosphere is disappearing. The next stage continues the cutting off of direct communication with the interior, separation takes place in the masses of magma, and local eruptions are still very violent. This phase may correspond with that stereotyped in the moon. The sixth stage begins, the seventh ocontinues, the deposit of sediments, during which metamorphism is active in the lower beds, thus forming an outer skin to the crust layer. Eruptions continue to affect a plateau type in the earlier of these; the volume of the reservoirs is gradually being reduced, as well as the communications with the more distant interior of the earth. The eighth, in which the liquid reservoirs are few and small, and communication from within any part oof the thickened crust layer to the interior very rarely exists, is the present period.

Ein Wort über den Sitz der vulkanischen Kräfte in der Gegenwart. (Mittheilung aus dem Museum für Volkerkunde zu Leipzig.)

Von Alphons Stübel. Pp. 15; 9 figures in text, 1 coloured plate. (Leipzig: Max Weg, 1901.)