The lithosphere, which is the rigid outermost shell of a planet (on Earth, the crust and upper mantle), is broken up into tectonic plates. On Earth, there are seven or eight major plates (depending on how they are defined) and many minor plates. Where plates meet, their relative motion determines the type of boundary; convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries. The lateral relative movement of the plates typically varies from zero to 100 mm annually. Movement of these tectonic plates can be one cause of earthquakes as happened recently in Nepal.
Having just mentioned Nepal……
My craft group have agreed to Knit for Nepal. This is really good news. Any Knitting comrades who would like to support this very worthy cause please get in touch.We plan to donate via an Orphaned child charity whose project is “Keep a child warm”. Watch this space for more information.