Quaternary
Movements
(One 2000th of life
history)
Repeated glaciations drive species thousands of kilometers.
Northern conifers reach gulf states.
Amazon basin a grassland; forest retreats to refugia.
Huge pluvial lakes in the West -- Death Valley a 180 meter deep lake.
Aral, Caspian and Black Seas merge.
Marsupials return to North America.