Lithospheric plates
The Earth has three main parts: the crust, the mantle and the core. The crust together with the uppermost rigid part of the mantle is called the lithosphere. The lithosphere is not one piece: it is broken into several large and many small plates. The plates drift very slowly, a few centimetres a year, on the softer, flowing layer of the mantle below, the asthenosphere. Where plates collide, pull apart or grind past each other there are many earthquakes and volcanoes; the “Ring of Fire” around the Pacific Ocean is such a zone. The place underground where a quake starts is the focus (hypocentre) and the point on the surface directly above it is the epicentre. A seismograph records the shaking. Quake strength is described in two ways: magnitude (Richter scale, a measure of released energy) and intensity, the effect at the surface (a 12-point scale is used in Uzbekistan).
Model: put two thick books side by side on a table with a thin sheet of paper or cloth between them, and slowly push them together. Watch how the paper wrinkles and rises – a model of mountains forming when plates collide. Safety: do not drop heavy books on feet or trap fingers between them; also discuss what to do in an earthquake (take cover by an inside wall or under a sturdy table, away from windows and heavy shelves).