The term 'HUGE SPANS' can be solved by the word 'EONS', which is a four-letter word. EONS are extremely long periods of time, usually measured in millions or billions of years. They are used to describe the immense amount of time that has passed since certain events occurred, such as the formation of the Earth or the extinction of dinosaurs. The term 'HUGE SPANS' is therefore an apt description for these incredibly long periods of time.