I'm going to tell you about a very scary phenomenon, about earthquakes. Usually, they happen suddenly, mostly in countries that are located near to the borders of the lithospheric plates. An earthquake is a shaking of the ground caused by a sudden movement of a large sections of earth, of tectonic or lithospheric plates. They cause injuries and deaths of a lot of people, they also damage a lot of buildings.
In our bid country earthquakes don't happen often ( mostly on Kamchatka and in the Kavkaz area). The situation is much worse in countries that are placed on islands ( Hawai, Japan, Caribs) or on the coast of big continents, for example Chile. The most powerful earthquake ever recorded, was in Chile on 22 May 1960. It was rated 9.5 on the magnitude scale.
Also, earthquakes can cause tsunami. There was a big earthquake and tsunami in Japan on 11 March 2011. It was very damaging, more than 15 thousands of people died.
Lately, more earthquakes happened in Chile, East Asia ( China) and Kamchatka.
In the Middle Ages people thought that earthquakes were punishment from God, they were afraid of them. Things have changed since then, but still people can't surely predict when exactly a strong earthquake would begin. In some countries there isn't enough of special supplies to warn and evacuate people. So be carefull, and if you get in to an earthquake then, If you are indoors, get yourself under a doorframe, or a large table, or other such object. If you are outdoors, remain in open ground away from any trees and buildings, and don't return indoors until the shaking ends.