The southern colonies came to rely on slavery to support their economy. what role did geography play in the spread of slavery in that region?

The geography determines the type of Commodities that the region able to produce.
In general, the regions that has the most slaves were commonly the region that managed to produce highly demanded agricultural products Such as cotton or Wheat. The slaves are an easy way to obtain cheap labor for the plantation

The southern colonies coastal ports made entry/exit easy for the slave trade. The southern colonies large amounts of fertile lands were ideal for slave work as well.