Is not my only possible practical aim the subduction of all that is Negro in me to the American?
The lines with barbs show zones of underthrusting (subduction), where one plate is sliding beneath another.
And from hence lastly doth arise the solidity of the section, by addition and subduction.
Subduction zones are found where one plate overrides, or subducts, another, pushing it downward into the mantle where it melts.
There are three types of plate boundaries: spreading zones, transform faults, and subduction zones.