The deep red hues observed in the Painted Desert in northern Arizona are caused by iron oxide found in various amounts throughout the sedimentary layers that exist here and is due to the same chemical reaction that causes rust. The desert covers an area 100 by 200 kilometres in size and experiences hot summers and cold winters. Not a particularly dry desert, it receives more than 25 centimetres of rainfall a year, which is more than that of many cities in the American Southwest.