Why did the planters of Virginia turn to chattel slavery?

Most of the original laborers of the Virginia colony were indentured servants. Indentured servitude served as a method for less wealthy people in England to fund their settlement in the New World. Essentially, indentured servants would sign up to work for the Virginia Company, or other estate owners, for seven years in return for passage to the new world and, often, shares in the company. These laborers were necessary to complete the backbreaking work in the tobacco fields necessary to fund the colonial enterprise.
However, by the end of the seventeenth century, there was a shortage of indentured servants. To fill the labor gap, more and more enslaved Africans were brought to the region to work the tobacco fields. There had been slaves in Virginia since 1619. However, for most of the century, indentured servants were considered more skilled and profitable than slaves.
By 1700, the shortage of people in England signing up to be indentured servants was causing their price to rise dramatically. Additionally, the tobacco industry had grown substantially. There just were not enough laborers to keep up with demand. At the same time, African slaves were coming down in price as the trade grew into a major transatlantic venture. It simply became more profitable for planters to use Africans as their main source of labor. While an indentured servant had a limited term of employment and would need to be replaced after his or her term was over, a slave would work for their entire life. They also could have children born into slavery, which meant that they became a self-sustaining source of labor.
African slaves were also treated much more poorly and were often worked much harder than indentured servants were. Feelings of racial superiority played into this. A slave owner usually had fewer qualms about mistreating and overworking a slave than a fellow Englishman. All this led to the rapid growth of slavery in Virginia. In 1670, there were about 2,000 slaves in Virginia. That number grew to 100,000 by 1750.
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