It is doubtful if the Earth’s crust exceeds, or equals 1,000 miles in
thickness. The outside is held from flying to pieces by the atmosphere,
which is a sort of tire to the earth, while the inside is constantly
pressing from effect of centrifugal force. These two factors must meet
somewhere.
On the outside, near the ice belt, the water pressure gets the best of
the inner forces and drives the waters into Symmes’s Hole. In the Earth
the centrifugal force has advantage until reaching the surface; but if
a big hole could be cut at the Equator through to the center, no doubt
a man could jump into it in safety and cease to fall as he cushioned
against centrifugal influence in his descent. Earthquakes are only the
effects of internal pressure of water to get to the surface, at times
bursting large reservoirs, producing tremblings, and at others with
great force throwing up hills and mountains from the tops of which the
fountains of water burst forth. At other times they are produced by
the contact of water with heated elements in volcanoes, creating the
commotion leading to the volcanic eruption, the latter of which can
only be produced by contact of fire and water.
It is believed that this is the complete and brief explanation of
earthquake causes.