In the final book of his poem Lucretius spends some time discussing earthquakes and their causes. In accordance with the standard Epicurean practice, Lucretius considers four alternative physical mechanisms that may be responsible for the phenomenon. The first three explanations involve three different kinds of subterranean matter—rock, water and air —causing the commotion of the earth's deeper regions, which is then transmitted to the surface. The fourth type of earthquake is different, as it is produced by the seismic agent affecting (...) the surface directly and potentially causing its deformation rather than just trembling. This happens when a gust of subterranean wind exagitata foras erumpitur et simul altamdiffindens terram magnum concinnat hiatum. (shrink)