What type of natural disaster is characterized by the shaking of the ground?

The shaking of the ground is a defining characteristic of an earthquake. Earthquakes occur when there is a sudden release of energy in the Earth's crust, resulting in seismic waves that cause the ground to shake. This release of energy often happens along fault lines, where tectonic plates interact.

In contrast, a volcano involves the eruption of molten rock, gas, and ash, which can occur without the ground shaking significantly. A tsunami, which is a large sea wave caused by underwater disturbances such as earthquakes or volcanic eruptions, may result from seismic activity but does not describe the shaking itself. A flood involves water overflowing onto normally dry land and is not associated with ground shaking. Thus, the specific defining feature of ground shaking makes earthquakes the correct answer for this question.