Compare this idea with H. P. Blavatsky's explanations for the other earths referred to in ancient scriptures. One such cycle is the sidereal year, which lasts 25,868 years and its relationship to periodic changes in the earth's axis and periodic changes in the global climate. One hundred years ago, scientists would have denied any violent shiftings of the earth's axis and its relation to climate. But modern geologists have changed their mind. The theory that variations in the Earth's orbit are responsible for triggering the advance and retreat of glaciers was developed by Yugoslavian scientist Milutin Milankovitch.
Modern geology recognizes many geological cycles.
There are episodic and periodic cycles. Episodic cycles recur irregularly and periodic cycles recur at fixed intervals. A volcanic eruption is episodic, but glacial periods, sea level changes and ice ages are claimed to be periodic. There are cyclical variations in the deposits of sediments that vary from centuries to a few million years. The main geological cycle that is considered by modern geologists to affect the surface of the earth is erosion, deposition of sediments, and folding and uplifting processes that form mountains.