How scientists can monitor radon gas emissions
Radon can give a clue to earthquake activity – but how does Italian scientist Giampaolo Giuliani measure the radioactive gas?
Radon is a radioactive gas, with no colour or smell. It is slightly heavier than air, chemically inert, and is made – after stages of decay and mutation – from uranium. Radon diffuses out of the earth in small, variable quantities all the time, but these can increase when reductions in pressure allow radon (or fluids carrying it in solution) to escape to the surface. Such pressure drops can accompany – or precede – the shearing of rocks in an earthquake.