Unstable ground under feet.
The lithosphere is divided into seven large and a couple of small plates, which are rigid, float like rafts on the underlying semi-molten mantle. The plates are moved by convection currents generated by heat from the centre of the Earth. At plate boundaries most of the major landforms occur. Also there are mainly located earthquake, volcanic and mountain-building zones.
Many big cities, like San Francisco, Los Angeles and Tokyo are located in those dangerous zones. Earthquakes are mainly located on the west shore of America (both North and South), south and central Africa, south Europe, Middle East and east Asia. They happen both in developed - USA, Japan, Italy, and in less developed countries – Armenia, Iran, India, and Mexico. And always they cause destruction and bring death with them. In Japan and in Chile there are over 10000 earthquakes every year.