Rensselaer Union, Volume 3, Number 15, Rensselaer, Jasper County, 5 January 1871 — The Phenomena of Earthquakes. [ARTICLE]

The Phenomena of Earthquakes.

In earthquake*, says the People t Mnqatine, we see the conservative agency of fire called in to "counteract the destructive agency of water. Wind and rain, heat and cold, are continually at work rending in pieces and grinding down the solid rock; the disintegrated portions of the rock form the soil of the lowlands, and this in its turn is eaten away by running streams, swept down by heavy rains, to be carried by the rivers and deposited in the sea. It is-thus that the shallows and great river deltas are formed; and the materials so brought down are gradually, by the action of the waves, distributed over the bed of the ocean. This action, if suffered to continue without interruption, would in time level the highest mountain ranges; and in the place of a varied surface of land and water there would be a uniform shallow sea covering the whole earth. Here the working of fire steps in to counteract the destructive agency of w T ater. It acts suddenly and with terrific force, nnd therefore it is more noted and more feared than the work which is done so silently and slowly, yet so irresistibly, by the gentle flow of the rivers. Of one thing we are sure, that they are caused by the internal heat of the earth. They usually occur in volcanic regions ; they arc frequently accompanied by volcanic eruptions; during their continuance flames arc said to burst from the earth, springs of boiling water rise from the sdil, and new volcanoes have been raised as their result. We know that at a com paratively small depth below the surface of the globe there is a temperature very far exceeding anything which w r e experience at the surface. Whether we accept the hypothesis of a vast central fire, or consider that this heat is generated by chemical .action or by electric currents, we know that there are stored up beneath our feet vast reservoirs of heat. What gases are stored under pressure in the cavities of the earth we know not. But we know that the increased expansive force of an elastic fluid under a comparatively small increase 01 temperature would be sufficient to rend asunder the solid rock and produce the effects we see. Perhaps a fissflre so opened may admit water to the heated nucleus, there to be instantly converted into steam with vast increase of volume. This exerting enormous pressure against the rocky walls of the cavity in which it is formed causes a wave of compression in the zone of the rock immediately surrounding it, and this wave is propagated onward through the rock, just as a wave travels through water. The confined fluid strikes the walls of its prison chamber a fierce blow, and this causes a shudder to run through the earth, which passes along the surface a shock, whose intensity is the only measure wo have of the forces causir git.