From Don Michels
Colin Stuart’s article on what makes planets ideal homes (15 March, p 38) could have included another important feature of Earth – tectonics. Renewing mountain ranges after the levelling by weather redistributes the elements and sustains the geochemical cycling.
Without tectonic cycling, our planet would become stagnant and close to homogeneous, with few niches for the abundant life forms we now have.
Missoula, Montana, US
