When geologists refer to the big five what are they referring to?

They're are reffering to a rapid decrease in the biodiversity on earth. ---> Extinction event

Master planned communities outside of chicago. note: population density means people living in an area per square mile. chicago, an urban and highly populated area has a much more higher density than a desert, amish community, settlement, or nomadic region.

Answerequatorial guinea,gabon, and western sahara;