Modern science has discovered that earthquakes occur when the internal forces of Earth are out of balance with those at its surface, sometimes resulting in surface ruptures and ground movement. These imbalances occur in many geological settings that result from the movement of lithospheric plates about Earths surface. The individual plates either converge (collide), or diverge (move away) and may do either at any angle to the plates bounding it, thus creating internal stresses. Another major cause is the movement of the plates over hotspots; which are areas where massive amounts of heat get transferred from Earths core. Rock melts when heat migrates upward, and the surrounding, weakened, lithosphere bends upward. Further faulting may occur after a volcanism when the volcano fall back into its empty magma chamber. Idaho contains much evidence for earthquake activity caused by tectonism and volcanism.
do animals seem to act so strangely before an earthquake?
It is quite common for animals to be seen engaging in bizarre behaviors right before an earthquake occurs. Examples of odd behaviors that have been observed include the following:
Animals are more sensitive to vibrations, magnetic fields, electricity, and odors than humans. This sensitivity may explain why they act so strangely before an earthquake. One theory suggests that just before a quake, microfractures are opening along the fault or stress zone. These are tiny ruptures occurring in surrounding rock, just before stresses reach the breaking point of an earthquake. It has been determined that the rupturing of microfractures actually can make very high pitched noises similar to shrieks. The sound is out of the human range of hearing, but could easily be heard by other, more sensitive species.