B - Senegal River. Borders Senegal and Mauritania
The more people that are migrating to urban areas (urbanization) needs more crops for the citizens which causes more people to grow crops and without crop rotating or methods to prevent soil degradation. More likely answer is that more industry grows in the urbanized areas and they have poor management of the soil which causes soil degradation<span />
There where two oceanic plates; the kula and farraloon plates about 300,000 to 360,000 years ago these two plates were pushed underneath the western edge of the north american plate
