The document discusses earthquakes, their causes, and one specific earthquake that occurred in Beijing in 2011. Earthquakes are caused by the movement and friction of tectonic plates deep within the earth. When the plates shift or collide, it releases tension in the rocks, sending shock waves that can damage buildings and infrastructure at the surface. The Beijing earthquake of June 15, 2011 toppled over 1,000 structures, killed at least 25 people, and injured 250, prompting a response from 25 firefighters.