A spread zone is an area whose geographical characteristics are conducive to the spread of language families across a large area, resulting in consecutive language replacement and low linguistic diversity (as opposed to a residual zone). The term was coined by linguist Johanna Nichols.
An example of a spread zone is northern Eurasia, where large areas (the Eurasian Steppe in particular) are covered by relatively few language families, most of which are possibly related to each other in a single superfamily (see Mitian).
- Nichols, Johanna. 1992. Linguistic diversity in space and time. Chicago: University of Chicago Press.