The Earth is said to have a molten core within an outer crust.

The greater part of the crust is covered by sea water.

The core and the crust are not homogeneous, that is not the same throughout.

Supposedly, the earth's core is cooling, causing changes in the crust. The crust evidently is made up of tectonic plates. Expansion/contraction, particularly where these plates  join or overlap, results in earthquakes, tsunamis and tidal waves.

We understand that changes within the core affect where the magnetic poles are located.

Ponder This ...

What impact does changes emanating from the core have on the earth's balance and does this contribute to changes in climate ?