Heat form the Earth's core,
Gravity,
The Pull of the Moon and Sun (tidal deformation),
and occasionally an incoming impactor.
Deformation
because of the folded deformation
It causes it to deform - this deformation is called "strain".
An earthquake is started when two plates (which lie under the Earths surface) rub together this creates movement which then sometimes pulls/pushes at the earths surface and creates giant cracks in the earths surface... and that is how an earthquake is started.
it creates the seasons.
Denudational processes, which includes, weathering, erosion, deformation, and exfoliation. Mass movement also plays a great role in changing the earths surface.
outer core
Few earthquakes happen in the earths mantle do to the fact that the mantle has a folded deformation. This means that the amount of pressure on the mantle caused it to deform.
The elastic force is caused by the deformation of an elastic material, such as a spring or rubber band, when it is stretched or compressed. This deformation creates a restoring force that tries to return the material to its original shape and position.
Any change in the volume or shape of Earth's crust is called crustal deformation. This can occur due to tectonic forces, such as compression, extension, or shearing, which lead to features like folding, faulting, and uplift.
day and night
it creates a tsunami