Such concentrations are usually created by geological events, such as volcanic eruptions and tectonic plate shifts that steer hot metal-bearing fluids into upper, accessible partsofthe Earth's crust, erosion, or massive sedimentary movements.
If this were to change, and theEarth became unstable, then partsofthe world could experience much greater temperature swings than we are used to through any given year, with freezing Arctic temperatures in winter followed by blazing hot temperatures in summer.