Last time popocatépetl volcano erupted?

According to the earth science reference tables, during which geologic time period were the continents of north america,south america, and africa closest together?

Why is the study of demography important to geographers

Which characteristics of temperature and salinity have the greatest influence on the movement of deep-ocean currentsa. warm and low salinityb. cold and high salinityc. cold and low salinityd. warm and high salinity