Why did much of the slave trade take place in the northern ports

What is the role of institutions in society - do they perform positive functions, or simply work in the interests of the powerful and against the powerless? (a related question here is why do our life chances vary by class, gender and ethnicity)

One of the results of the 2010 golf of mexico oil spill is the threat to various species in the goths ecosystem it disturbed and in some cases forever altered the of the gulf coast

The principle that the geoglical processes that we see today have occurred through out earths history is called