Unite the country under the rule of a single, Communist government
Your answer would be Tectonic.
Tectonic plates move in various directions, and move slowly. Due to the movement of tectonic plates the earth cracks, and shakes which is called an earch quake. Tectonic plates move constently everyday, and you can't feel it because it's slow. Wehn tectonic plates move quickly, the earth starts to shake. The most common places that have tectonic plates have a higher chance of having an earthquake, even a tusnami.
High levels of dissolved oxygen
